- Volume 149, Issue 7, 2003
Volume 149, Issue 7, 2003
- Review
-
-
-
Eukaryotic-type protein kinases in Streptomyces coelicolor: variations on a common theme
More LessThe increasing number of genes encoding eukaryotic-type Ser/Thr protein kinases (ESTPKs) in prokaryotes, identified mostly due to genome-sequencing projects, suggests that these enzymes play an indispensable role in many bacterial species. Some prokaryotes, such as Streptomyces coelicolor, carry numerous genes of this type. Though the regulatory pathways have been intensively studied in the organism, experimental proof of the physiological function of ESTPKs is scarce. This review presents a family portrait of the genes identified in the sequence of the S. coelicolor A3(2) genome. Based on the available experimental data on ESTPKs in streptomycetes and related bacteria, and on computer-assisted sequence analyses, possible roles of these enzymes in the regulation of cellular processes in streptomycetes are suggested.
-
-
- Microbiology Comment
-
- Cell And Developmental Biology
-
-
-
Patchiness of murein insertion into the sidewall of Escherichia coli
More LessThis paper extends, with computer techniques, the authors' previous work on the kinetics of pole wall and sidewall synthesis in Escherichia coli. These findings extend the conclusion that the nascent poles are made of entirely new material and that no new material is inserted into old poles. This requires re-evaluation of ideas in the literature about wall growth and cell division. Mechanisms of various types have been suggested for the growth of Gram-negative rod-shaped bacteria and these will also require major re-evaluation because of the finding, reported here, that the sidewall is made in several modes: patches of new murein, bands of new material largely going circumferentially around the cell, and areas of the sidewall that are enlarged by an intimate and regular admixture of new with the old muropeptides.
-
-
- Biochemistry And Molecular Biology
-
-
-
Posttranslational processing of the xylanase Xys1L from Streptomyces halstedii JM8 is carried out by secreted serine proteases
The xylanase Xys1L from Streptomyces halstedii JM8 is known to be processed extracellularly, to produce a protein of 33·7 kDa, Xys1S, that retains catalytic activity but not its cellulose-binding capacity. This paper demonstrates that at least five serine proteases isolated from Streptomyces spp. have the ability to process the xylanase Xys1L. The genes of two of these extracellular serine proteases, denominated SpB and SpC, were cloned from Streptomyces lividans 66 (a strain commonly used as a host for protein secretion), sequenced, and overexpressed in S. lividans; both purified proteases were able to process Xys1L in vitro. Three other previously reported purified Streptomyces serine proteases, SAM-P20, SAM-P26 and SAM-P45, also processed Xys1L in vitro. The involvement of serine proteases in xylanase processing-degradation in vivo was demonstrated by co-expression of the xylanase gene (xysA) and the gene encoding the serine protease inhibitor (SLPI) from S. lividans. Co-expression prevented processing and degradation of Xys1L and resulted in a threefold increase in the xylanase activity present in the culture supernatant. SpB and SpC also have the capacity to process other secreted proteins such as p40, a cellulose-binding protein from S. halstedii JM8, but do not have any clear effect on other secreted proteins such as amylase (Amy) from Streptomyces griseus and xylanase Xyl30 from Streptomyces avermitilis.
-
-
-
-
Cloning, sequencing and heterologous expression of the medermycin biosynthetic gene cluster of Streptomyces sp. AM-7161: towards comparative analysis of the benzoisochromanequinone gene clusters
More LessMedermycin is a Streptomyces aromatic C-glycoside antibiotic classified in the benzoisochromanequinones (BIQs), which presents several interesting biosynthetic problems concerning polyketide synthase (PKS), post-PKS tailoring and deoxysugar pathways. The biosynthetic gene cluster for medermycin (the med cluster) was cloned from Streptomyces sp. AM-7161. Completeness of the clone was proved by the heterologous expression of a cosmid carrying the entire med cluster in Streptomyces coelicolor CH999 to produce medermycin. The DNA sequence of the cosmid (36 202 bp) revealed 34 complete ORFs, with an incomplete ORF at either end. Functional assignment of the deduced products was made for PKS and biosynthetically related enzymes, tailoring steps including strereochemical control, oxidation, angolosamine pathway, C-glycosylation, and regulation. The med cluster was estimated to be about 30 kb long, covering 29 ORFs. An unusual characteristic of the cluster is the disconnected organization of the minimal PKS genes: med-ORF23 encoding the acyl carrier protein is 20 kb apart from med-ORF1 and med-ORF2 for the two ketosynthase components. Secondly, the six genes (med-ORF14, 15, 16, 17, 18 and 20) for the biosynthesis of the deoxysugar, angolosamine, are all contiguous. Finally, the finding of a glycosyltransferase gene, med-ORF8, suggests a possible involvement of conventional C-glycosylation in medermycin biosynthesis. Comparison among the three complete BIQ gene clusters – med and those for actinorhodin (act) and granaticin (gra) – revealed some common genes whose deduced functions are unavailable from database searches (the ‘unknowns’). An example is med-ORF5, a homologue of actVI-ORF3 and gra-ORF18, which was highlighted by a recent proteomic analysis of S. coelicolor A3(2).
-
-
-
Complexes of the uracil-DNA glycosylase inhibitor protein, Ugi, with Mycobacterium smegmatis and Mycobacterium tuberculosis uracil-DNA glycosylases
More LessUracil, a promutagenic base, appears in DNA either by deamination of cytosine or by incorporation of dUMP by DNA polymerases. This unconventional base in DNA is removed by uracil-DNA glycosylase (UDG). Interestingly, a bacteriophage-encoded short polypeptide, UDG inhibitor (Ugi), specifically inhibits UDGs by forming a tight complex. Three-dimensional structures of the complexes of Ugi with UDGs from Escherichia coli, human and herpes simplex virus have shown that two of the structural elements in Ugi, the hydrophobic pocket and the β1-edge, establish key interactions with UDGs. In this report the characterization of complexes of Ugi with UDGs from Mycobacterium tuberculosis, a pathogenic bacterium, and Mycobacterium smegmatis, a widely used model organism for the former, is described. Unlike the E. coli (Eco) UDG-Ugi complex, which is stable to treatment with 8 M urea, the mycobacterial UDG-Ugi complexes dissociate in 5–6 M urea. Furthermore, the Ugi from the complexes of mycobacterial UDGs can be exchanged by the DNA substrate. Interestingly, while EcoUDG sequestered Ugi into the EcoUDG-Ugi complex when incubated with mycobacterial UDG-Ugi complexes, even a large excess of mycobacterial UDGs failed to sequester Ugi from the EcoUDG-Ugi complex. However, the M. tuberculosis (Mtu) UDG-Ugi complex was seen when MtuUDG was incubated with M. smegmatis (Msm) UDG-Ugi or EcoUDG(L191G)-Ugi complexes. The reversible nature of the complexes of Ugi with mycobacterial UDGs (which naturally lack some of the structural elements important for interaction with the β1-edge of Ugi) and with mutants of EcoUDG (which are deficient in interaction with the hydrophobic pocket of Ugi) highlights the significance of both classes of interaction in formation of UDG-Ugi complexes. Furthermore, it is shown that even though mycobacterial UDG-Ugi complexes dissociate in 5–6 M urea, Ugi is still a potent inhibitor of UDG activity in mycobacteria.
-
-
-
Genetic dissection of trehalose biosynthesis in Corynebacterium glutamicum: inactivation of trehalose production leads to impaired growth and an altered cell wall lipid composition
More LessThe analysis of the available Corynebacterium genome sequence data led to the proposal of the presence of all three known pathways for trehalose biosynthesis in bacteria, i.e. trehalose synthesis from UDP-glucose and glucose 6-phosphate (OtsA-OtsB pathway), from malto-oligosaccharides or α-1,4-glucans (TreY-TreZ pathway), or from maltose (TreS pathway). Inactivation of only one of the three pathways by chromosomal deletion did not have a severe impact on C. glutamicum growth, while the simultaneous inactivation of the OtsA-OtsB and TreY-TreZ pathway or of all three pathways resulted in the inability of the corresponding mutants to synthesize trehalose and to grow efficiently on various sugar substrates in minimal media. This growth defect was largely reversed by the addition of trehalose to the culture broth. In addition, a possible pathway for glycogen synthesis from ADP-glucose involving glycogen synthase (GlgA) was discovered. C. glutamicum was found to accumulate significant amounts of glycogen when grown under conditions of sugar excess. Insertional inactivation of the chromosomal glgA gene led to the failure of C. glutamicum cells to accumulate glycogen and to the abolition of trehalose production in a ΔotsAB background, demonstrating that trehalose production via the TreY-TreZ pathway is dependent on a functional glycogen biosynthetic route. The trehalose-non-producing mutant with inactivated OtsA-OtsB and TreY-TreZ pathways displayed an altered cell wall lipid composition when grown in minimal broth in the absence of trehalose. Under these conditions, the mutant lacked both major trehalose-containing glycolipids, i.e. trehalose monocorynomycolate and trehalose dicorynomycolate, in its cell wall lipid fraction. The results suggest that a dramatically altered cell wall lipid bilayer of trehalose-less C. glutamicum mutants may be responsible for the observed growth deficiency of such strains in minimal medium. The results of the genetic and physiological dissection of trehalose biosynthesis in C. glutamicum reported here may be of general relevance for the whole phylogenetic group of mycolic-acid-containing coryneform bacteria.
-
-
-
Phospholipid composition of several clinically relevant Corynebacterium species as determined by mass spectrometry: an unusual fatty acyl moiety is present in inositol-containing phospholipids of Corynebacterium urealyticum
More LessA comparative study on phospholipids of Corynebacterium amycolatum, Corynebacterium jeikeium and Corynebacterium urealyticum was carried out using fast-atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometry. Data obtained indicate the presence of acylphosphatidylglycerol (APG), diphosphatidylglycerol, phosphatidylglycerol (PG), phosphatidylinositol (PI) and triacylphosphatidylinositol dimannosides (Ac3PIM2) in these bacteria. In general, octadecenoyl and hexadecanoyl fatty acyl moieties predominated in phospholipids of C. amycolatum, whereas high levels of hexadecenoyl were found in C. jeikeium and C. urealyticum. Mass spectra from purified APG and PG indicated that the sn-1 position of the glycerol was occupied by octadecenoyl in the three species studied. Notably, several major molecular species of PI and Ac3PIM2 from C. urealyticum contained significant amounts of a moiety identified as 10-methyleneoctadecanoyl, located at the sn-1 position of these molecules. On the other hand, multiantibiotic resistant and susceptible strains of C. amycolatum differed in several minor phospholipid fatty acids of 19 carbon atoms, identified as 10-methyloctadecenoic, 10-methyloctadecanoic (tuberculostearic acid) and 10-methyleneoctadecanoic. The results demonstrate an overall similarity among the phospholipids of the different species studied but also significant differences related to the acyl chains of the glycerol moiety of these compounds, notably the high levels of an unusual fatty acyl moiety in inositol-containing phospholipids of C. urealyticum.
-
-
-
Phosphoenolpyruvate phosphotransferase system and N-acetylglucosamine metabolism in Bacillus sphaericus
More LessBacillus sphaericus, a bacterium of biotechnological interest due to its ability to produce mosquitocidal toxins, is unable to use sugars as carbon source. However, ptsHI genes encoding HPr and EI proteins belonging to a PTS were cloned, sequenced and characterized. Both HPr and EI proteins were fully functional for phosphoenolpyruvate-dependent transphosphorylation in complementation assays using extracts from Staphylococcus aureus mutants for one of these proteins. HPr(His6) was purified from wild-type and a Ser46/Gln mutant of B. sphaericus, and used for in vitro phosphorylation experiments using extracts from either B. sphaericus or Bacillus subtilis as kinase source. The results showed that both phosphorylated forms, P-Ser46-HPr and P-His15-HPr, could be obtained. The findings also proved indirectly the existence of an HPr kinase activity in B. sphaericus. The genetic structure of these ptsHI genes has some unusual features, as they are co-transcribed with genes encoding metabolic enzymes related to N-acetylglucosamine (GlcNAc) catabolism (nagA, nagB and an undetermined orf2). In fact, this bacterium was able to utilize this amino sugar as carbon and energy source, but a ptsH null mutant had lost this characteristic. Investigation of GlcNAc uptake and streptozotocin inhibition in both a wild-type and a ptsH null mutant strain led to the proposal that GlcNAc is transported and phosphorylated by an EIINag element of the PTS, as yet uncharacterized. In addition, GlcNAc-6-phosphate deacetylase and GlcN-6-phosphate deaminase activities were determined; both were induced in the presence of GlcNAc. These results, together with the authors' recent findings of the presence of a phosphofructokinase activity, are strongly indicative of a glycolytic pathway in B. sphaericus. They also open new possibilities for genetic improvements in industrial applications.
-
-
-
The sulfane sulfur of persulfides is the actual substrate of the sulfur-oxidizing enzymes from Acidithiobacillus and Acidiphilium spp.
More LessTo identify the actual substrate of the glutathione-dependent sulfur dioxygenase (EC 1.13.11.18) elemental sulfur oxidation of the meso-acidophilic Acidithiobacillus thiooxidans strains DSM 504 and K6, Acidithiobacillus ferrooxidans strain R1 and Acidiphilium acidophilum DSM 700 was analysed. Extraordinarily high specific sulfur dioxygenase activities up to 460 nmol min−1 (mg protein)−1 were found in crude extracts. All cell-free systems oxidized elemental sulfur only via glutathione persulfide (GSSH), a non-enzymic reaction product from glutathione (GSH) and elemental sulfur. Thus, GSH plays a catalytic role in elemental sulfur activation, but is not consumed during enzymic sulfane sulfur oxidation. Sulfite is the first product of sulfur dioxygenase activity; it further reacted non-enzymically to sulfate, thiosulfate or glutathione S-sulfonate (). Free sulfide was not oxidized by the sulfur dioxygenase. Persulfide as sulfur donor could not be replaced by other sulfane-sulfur-containing compounds (thiosulfate, polythionates, bisorganyl-polysulfanes or monoarylthiosulfonates). The oxidation of H2S by the dioxygenase required GSSG, i.e. the disulfide of GSH, which reacted non-enzymically with sulfide to give GSSH prior to enzymic oxidation. On the basis of these results and previous findings a biochemical model for elemental sulfur and sulfide oxidation in Acidithiobacillus and Acidiphilium spp. is proposed.
-
-
-
The haem pigment of the oral anaerobes Prevotella nigrescens and Prevotella intermedia is composed of iron(III) protoporphyrin IX in the monomeric form
More LessThe haem pigment of Porphyromonas gingivalis is composed of μ-oxo bishaem, [Fe(III)PPIX]2O, but the nature of that generated by Prevotella species has not been established. Mössbauer, Raman and UV-visible spectrophotometry were used to characterize the haem pigment of Prevotella intermedia and Prevotella nigrescens. Mössbauer and Raman spectroscopy revealed the major haem species to be monomeric iron protoporphyrin IX, Fe(III)PPIX.OH (haematin). The terminal growth pH of both species on blood agar was between 5·8 and 6·0, which favours the formation and maintenance of monomeric Fe(III)PPIX.OH. Incubation of Pr. nigrescens and Pr. intermedia with oxyhaemoglobin at pH 6·5 resulted in formation of aquomethaemoglobin which was degraded to generate Fe(III)PPIX.OH which in turn became cell-associated, whilst incubation at pH 7·5 resulted in formation of [Fe(III)PPIX]2O. It is concluded that both Prevotella species degrade oxyhaemoglobin to form [Fe(III)PPIX]2O as an intermediate, which is converted to Fe(III)PPIX.OH through a depression in pH. The low pH encourages cell-surface deposition of insoluble Fe(III)PPIX.OH which would act as a barrier against oxygen and reactive oxygen species, and also protect against H2O2 through its inherent catalase activity.
-
-
-
Rapid identification of Gram-positive anaerobic coccal species originally classified in the genus Peptostreptococcus by multiplex PCR assays using genus- and species-specific primers
More LessHere, a rapid and reliable two-step multiplex PCR assay for identifying 14 Gram-positive anaerobic cocci (GPAC) species originally classified in the genus Peptostreptococcus (Anaerococcus hydrogenalis, Anaerococcus lactolyticus, Anaerococcus octavius, Anaerococcus prevotii, Anaerococcus tetradius, Anaerococcus vaginalis, Finegoldia magna, Micromonas micros, Peptostreptococcus anaerobius, Peptoniphilus asaccharolyticus, Peptoniphilus harei, Peptoniphilus indolicus, Peptoniphilus ivorii and Peptoniphilus lacrimalis) is reported. Fourteen type strains representing 14 GPAC species were first identified to the genus level by multiplex PCR (multiplex PCR-G). Since three of these genera (Finegoldia, Micromonas and Peptostreptococcus) contain only a single species, F. magna, M. micros and P. anaerobius, respectively, these organisms were identified to the species level directly by using the multiplex PCR-G. Then six species of the genus Anaerococcus (A. hydrogenalis, A. lactolyticus, A. octavius, A. prevotii, A. vaginalis and A. tetradius) were further identified to the species level using multiplex PCR assays (multiplex PCR-Ia and multiplex PCR-Ib). Similarly, five species of the genus Peptoniphilus (Pn. asaccharolyticus, Pn. harei, Pn. indolicus, Pn. ivorii and Pn. lacrimalis) were identified to the species level using multiplex PCR-IIa and multiplex PCR-IIb. The established two-step multiplex PCR identification scheme was applied to the identification of 190 clinical isolates of GPAC species that had been identified previously to the species level by 16S rRNA sequencing and phenotypic tests. The identification obtained from multiplex PCR assays showed 100 % agreement with 16S rDNA sequencing identification, but only 65 % (123/190) agreement with the identification obtained by phenotypic tests. The multiplex PCR scheme established in this study is a simple, rapid and reliable method for the identification of GPAC species. It will permit a more accurate assessment of the role of various GPAC species in infection and of the degree of antimicrobial resistance in each of the group members.
-
-
-
Bacterial lactoferrin-binding protein A binds to both domains of the human lactoferrin C-lobe
More LessPathogenic bacteria in the family Neisseriaceae express surface receptors to acquire iron from the mammalian iron-binding proteins. Transferrins and lactoferrins constitute a family of iron-binding proteins highly related in both sequence and structure, yet the bacterial receptors are able to distinguish between these proteins and uphold a strict binding specificity. In order to understand the molecular basis for this specificity, the interaction between human lactoferrin (hLf) and the lactoferrin-binding protein A (LbpA) from Moraxella catarrhalis was studied. A periplasmic expression system was designed for the heterologous expression of LbpA, which enabled the investigation of its binding activity in the absence of lactoferrin-binding protein B (LbpB). To facilitate delineation of the LbpA-binding regions of hLf, chimeric proteins composed of hLf and bovine transferrin were made. Binding studies performed with the chimeric proteins and recombinant LbpA identified two binding regions within the C-terminus of hLf. Furthermore, native LbpA from Moraxella and Neisseria spp. bound the identical spectrum of hybrid proteins as the recombinant receptor, demonstrating a conserved binding interaction with the C-lobe of hLf.
-
-
-
The paradoxical cyanide-stimulated respiration of Zymomonas mobilis: cyanide sensitivity of alcohol dehydrogenase (ADH II)
More LessThe respiratory inhibitor cyanide stimulates growth of the ethanologenic bacterium Zymomonas mobilis, perhaps by diverting reducing equivalents from respiration to ethanol synthesis, thereby minimizing accumulation of toxic acetaldehyde. This study sought to identify cyanide-sensitive components of respiration. In aerobically grown, permeabilized Z. mobilis cells, addition of 200 μM cyanide caused gradual inhibition of ADH II, the iron-containing alcohol dehydrogenase isoenzyme, which, in aerobic cultures, might be oxidizing ethanol and supplying NADH to the respiratory chain. In membrane preparations, NADH oxidase was inhibited more rapidly, but to a lesser extent, than ADH II. The time-course of inhibition of whole-cell respiration resembled that of NADH oxidase, yet the inhibition was almost complete, and was accompanied by an increase of intracellular NADH concentration. Cyanide did not significantly affect the activity of ADH I, the zinc-containing alcohol dehydrogenase isoenzyme. When an aerobic batch culture was grown in the presence of 200 μM cyanide, cyanide-resistant ADH II activity was observed, its appearance correlating with the onset of respiration. It is concluded that the membrane-associated respiratory chain, but not ADH II, is responsible for the whole-cell cyanide sensitivity, while the cyanide-resistant ADH II is needed for respiration in the presence of cyanide, and represents an adaptive response of Z. mobilis to cyanide, analogous to the induction of alternative terminal oxidases in other bacteria.
-
-
-
Different roles for the stress-activated protein kinase pathway in the regulation of trehalose metabolism in Schizosaccharomyces pombe
More LessThe Wis1p-Sty1p mitogen-activated protein kinase cascade is a major signalling system in the fission yeast Schizosaccharomyces pombe for a wide range of stress responses. It is known that trehalose functions as a protective metabolite to counteract deleterious effects of environmental stresses. Herein it is reported that the expression of genes related to trehalose metabolism in S. pombe, ntp1 + (neutral trehalase) and tps1 + [trehalose-6-phosphate (T6P) synthase], is partially regulated by the Sty1p kinase under salt-induced osmotic stress and conditions of slight oxidative stress and is fully dependent on this kinase under severe oxidative stress. This control is carried out through transcription factors Atf1p/Pcr1p during osmotic stress and through Pap1p during exposure to low levels of oxidative stress. However, all three transcription factors are needed for gene expression under conditions of extreme oxidative stress. In addition, a role for Sty1p in the modulation of post-transcriptional activation of trehalase mediated by Pka1p/Sck1p kinases, as well as in the activity of T6P synthase under such stressful conditions has been demonstrated. These results reveal a novel dual action of the Wis1p-Sty1p pathway in the regulation of trehalose metabolism in fission yeast.
-
- Genes And Genomes
-
-
-
Involvement of the cgtA gene function in stimulation of DNA repair in Escherichia coli and Vibrio harveyi
More LessCgtA is a member of the Obg/Gtp1 subfamily of small GTP-binding proteins. CgtA homologues have been found in various prokaryotic and eukaryotic organisms, ranging from bacteria to humans. Nevertheless, despite the fact that cgtA is an essential gene in most bacterial species, its function in the regulation of cellular processes is largely unknown. Here it has been demonstrated that in two bacterial species, Escherichia coli and Vibrio harveyi, the cgtA gene product enhances survival of cells after UV irradiation. Expression of the cgtA gene was found to be enhanced after UV irradiation of both E. coli and V. harveyi. Moderate overexpression of cgtA resulted in higher UV resistance of E. coli wild-type and dnaQ strains, but not in uvrA, uvrB, umuC and recA mutant hosts. Overexpression of the E. coli recA gene in the V. harveyi cgtA mutant, which is very sensitive to UV light, restored the level of survival of UV-irradiated cells to the levels observed for wild-type bacteria. Moreover, the basal level of the RecA protein was lower in a temperature-sensitive cgtA mutant of E. coli than in the cgtA + strain, and contrary to wild-type bacteria, no significant increase in recA gene expression was observed after UV irradiation of this cgtA mutant. Finally, stimulation of uvrB gene transcription under these conditions was impaired in the V. harveyi cgtA mutant. All these results strongly suggest that the cgtA gene product is involved in DNA repair processes, most probably by stimulation of recA gene expression and resultant activation of RecA-dependent DNA repair pathways.
-
-
-
-
rpoN, mmoR and mmoG, genes involved in regulating the expression of soluble methane monooxygenase in Methylosinus trichosporium OB3b
More LessThe methanotrophic bacterium Methylosinus trichosporium OB3b converts methane to methanol using two distinct forms of methane monooxygenase (MMO) enzyme: a cytoplasmic soluble form (sMMO) and a membrane-bound form (pMMO). The transcription of these two operons is known to proceed in a reciprocal fashion with sMMO expressed at low copper-to-biomass ratios and pMMO at high copper-to-biomass ratios. Transcription of the smmo operon is initiated from a σ N promoter 5′ of mmoX. In this study the genes encoding σ N (rpoN) and a typical σ N-dependent transcriptional activator (mmoR) were cloned and sequenced. mmoR, a regulatory gene, and mmoG, a gene encoding a GroEL homologue, lie 5′ of the structural genes for the sMMO enzyme. Subsequent mutation of rpoN and mmoR by marker-exchange mutagenesis resulted in strains Gm1 and JS1, which were unable to express functional sMMO or initiate transcription of mmoX. An rpoN mutant was also unable to fix nitrogen or use nitrate as sole nitrogen source, indicating that σ N plays a role in both nitrogen and carbon metabolism in Ms. trichosporium OB3b. The data also indicate that mmoG is transcribed in a σ N- and MmoR-independent manner. Marker-exchange mutagenesis of mmoG revealed that MmoG is necessary for smmo gene transcription and activity and may be an MmoR-specific chaperone required for functional assembly of transcriptionally competent MmoR in vivo. The data presented allow the proposal of a more complete model for copper-mediated regulation of smmo gene expression.
-
-
-
Genes involved in the copper-dependent regulation of soluble methane monooxygenase of Methylococcus capsulatus (Bath): cloning, sequencing and mutational analysis
More LessThe key enzyme in methane metabolism is methane monooxygenase (MMO), which catalyses the oxidation of methane to methanol. Some methanotrophs, including Methylococcus capsulatus (Bath), possess two distinct MMOs. The level of copper in the environment regulates the biosynthesis of the MMO enzymes in these methanotrophs. Under low-copper conditions, soluble MMO (sMMO) is expressed and regulation takes place at the level of transcription. The structural genes of sMMO were previously identified as mmoXYBZ, mmoD and mmoC. Putative transcriptional start sites, containing a σ 70- and a σ N-dependent motif, were identified in the 5′ region of mmoX. The promoter region of mmoX was mapped using truncated 5′ end regions fused to a promoterless green fluorescent protein gene. A 9·5 kb region, adjacent to the sMMO structural gene cluster, was analysed. Downstream (3′) from the last gene of the operon, mmoC, four ORFs were found, mmoG, mmoQ, mmoS and mmoR. mmoG shows significant identity to the large subunit of the bacterial chaperonin gene, groEL. In the opposite orientation, two genes, mmoQ and mmoS, showed significant identity to two-component sensor–regulator system genes. Next to mmoS, a gene encoding a putative σ N-dependent transcriptional activator, mmoR was identified. The mmoG and mmoR genes were mutated by marker-exchange mutagenesis and the effects of these mutations on the expression of sMMO was investigated. sMMO transcription was impaired in both mutants. These results indicate that mmoG and mmoR are essential for the expression of sMMO in Mc. capsulatus (Bath).
-
-
-
Identification of genes in the tomato big bud phytoplasma and comparison to those in sweet potato little leaf-V4 phytoplasma
More LessGenetic relatedness of phytoplasmas is commonly defined on the basis of differences in the highly conserved 16S rRNA gene, which may not resolve closely related phytoplasmas. An example of this is the closely related tomato big bud (TBB) and sweet potato little leaf strain V4 (SPLL-V4) phytoplasmas, which cannot easily be differentiated by their 16S rRNA gene sequences. This study aimed to identify genes on the TBB phytoplasma chromosome which could be used to examine genetic variation between these two closely related phytoplasmas. Random clones generated from TBB phytoplasma genomic DNA were sequenced and characterized by database analysis. Twenty-three genes were identified within 19 random clones, which contained approximately 18·0 kbp of TBB phytoplasma genomic DNA. Half of the TBB phytoplasma genes identified were involved in DNA replication, transcription and translation. The remaining TBB phytoplasma genes were involved in protein secretion, cellular processes and energy metabolism. Phylogenetic analysis of representative genes showed that the TBB phytoplasma grouped with the mycoplasmas with the exception of the TBB phytoplasma secA gene, which grouped with the onion yellows phytoplasma. PCR primers were designed based on the new genes and tested on isolates of the TBB and SPLL-V4 phytoplasmas. Most primers amplified a product from TBB and SPLL-V4 phytoplasma samples. When amplified products were subjected to RFLP analysis, the restriction patterns were the same as the respective original clones. This result confirmed that the same sequence had been amplified by PCR and showed that these isolates were indistinguishable using the new genes. This study showed that in fact the TBB and SPLL-V4 phytoplasmas are closely related even with the analysis of new genes. These new genes have, however, provided insight into the biology of the TBB and SPLL-V4 phytoplasmas.
-
-
-
An enhanced GFP reporter system to monitor gene expression in Borrelia burgdorferi
More LessBorrelia burgdorferi regulates genes in response to a number of environmental signals such as temperature and pH. A green fluorescent protein (GFP) reporter system using the ospC, ospA and flaB promoters from B. burgdorferi B31 was introduced into infectious clonal isolates of strains B31 and N40 to monitor and compare gene expression in response to pH and temperature in vitro. GFP could be assayed by epifluorescence microscopy, immunoblotting or spectrofluorometry and was an accurate reporter of target gene expression. It was determined that only 179 bp 5′ of ospC was sufficient to regulate the reporter gfp in vitro in response to pH and temperature in B. burgdorferi B31. The loss of linear plasmid (lp) 25, lp28-1, lp36 and lp56 had no effect on the ability of B. burgdorferi B31 to regulate ospC in response to pH or temperature. The amount of OspC in N40 transformants was unaffected by changes in pH or temperature of the culture medium. This suggests that regulation of gene expression in response to pH and temperature may vary between these two B. burgdorferi strains.
-
- Pathogens And Pathogenicity
-
-
-
pckA-deficient Mycobacterium bovis BCG shows attenuated virulence in mice and in macrophages
More LessPhosphoenolpyruvate carboxykinase (PEPCK) catalyses the reversible decarboxylation and phosphorylation of oxaloacetate (OAA) to form phosphoenolpyruvate (PEP). In this study, the regulation of the PEPCK-encoding gene pckA was examined through the evaluation of green fluorescent protein expression driven by the pckA promoter. The results showed that pckA was upregulated by acetate or palmitate but downregulated by glucose. Deletion of the pckA gene of Mycobacterium bovis BCG led to a reduction in the capacity of the bacteria to infect and survive in macrophages. Moreover, mice infected with ΔpckA BCG were able to reduce the bacterial load much more effectively than mice infected with the parental wild-type bacteria. This attenuated virulence was reflected in the degree of pathology, where granuloma formation was diminished both in numbers and degree. The data indicate that PEPCK activity is important during establishment of infection. Whether its role is in the gluconeogenic pathway for carbohydrate formation or in the conversion of PEP to OAA to maintain the TCA cycle remains to be determined.
-
-
-
-
Virulence attenuation of two Mas-like polyketide synthase mutants of Mycobacterium tuberculosis
The cell envelope of pathogenic mycobacteria is highly distinctive in that it contains a large number of structurally related very long multiple methyl-branched fatty acids. These complex molecules are thought to play important roles in cell envelope organization and virulence. The genetic and enzymic characterization of the polyketide synthase Mas, which is responsible for the synthesis of one such family of fatty acids (the mycocerosic acids), paved the way towards the identification of other enzymes involved in the synthesis of methyl-branched fatty acids in M. tuberculosis. In an effort to elucidate the origin of these complex fatty acids and their possible involvement in pathogenesis, the two mas-like polyketide genes pks5 and pks7 were disrupted in M. tuberculosis and the effects of their inactivation on fatty acid composition and virulence were analysed. While the disruption of pks7 resulted in a mutant deficient in the production of phthiocerol dimycocerosates, the cell envelope composition of the pks5 mutant was found to be identical to that of the wild-type parental strain M. tuberculosis H37Rv. Interestingly, both the pks5 and pks7 mutants displayed severe growth defects in mice.
-
-
-
Antigenic diversity of meningococcal enterobactin receptor FetA, a vaccine component
More LessMeningococcal FetA (FrpB), an iron-regulated outer-membrane protein and vaccine component, was shown to be highly diverse: a total of 60 fetA alleles, encoding 56 protein sequences, were identified from 107 representative Neisseria meningitidis isolates. Phylogenetic analysis established that the allelic variants had been generated by both point mutation and horizontal genetic exchange. Nucleotide substitution was unevenly distributed in the gene, which contained both conserved and variable sequence regions. The most conserved region of the translated peptide sequence corresponded to an amino-terminal domain of the protein and the most diverse region to a previously identified variable region (VR). A nomenclature system for the peptides encoded by the VR was devised which classified 24 variants into 5 FetA variant families. On the basis of these data, murine polyclonal sera specific for four FetA variants were generated. The reactivities of these sera in whole-cell ELISA experiments were consistent with the hypothesis that the VR encoded an immunodominant epitope and indicated that the sera reacted mainly with variants against which they were raised. The diversity of this protein is likely to limit its effectiveness as a vaccine component.
-
-
-
Production of the signalling molecule, autoinducer-2, by Neisseria meningitidis: lack of evidence for a concerted transcriptional response
More LessNeisseria meningitidis is a Gram-negative bacterium which is an important causative agent of septicaemia and meningitis. LuxS has been shown to be involved in the biosynthesis of a quorum sensing molecule, autoinducer-2 (AI-2), known to play a role in virulence in Escherichia coli, as well as other bacteria. Evidence that serogroup B of N. meningitidis produces AI-2, along with the observation that a luxS mutant of this strain had attenuated virulence in an infant rat model of bacteraemia, led to further investigation of the role of this quorum sensing molecule in N. meningitidis. In this study, it is demonstrated that AI-2 is not involved in regulating growth of meningococci, either in culture or in contact with epithelial cells. Furthermore, transcriptional profiling using DNA microarrays shows an absence of the concerted regulation seen in other bacteria. Taken together, these data suggest that in N. meningitidis, AI-2 may be a metabolic by-product and not a cell-to-cell signalling molecule.
-
-
-
The Escherichia coli AIDA autotransporter adhesin recognizes an integral membrane glycoprotein as receptor
More LessThe AIDA-I autotransporter adhesin, as a prototype of the AIDA adhesin family, represents a tripartite antigen consisting of the functional adhesin AIDA-I (α-domain), which mediates the specific attachment of bacteria to target cells, and a two-domain translocator (AIDAc) organized in the β 1- and β 2-domains. Cellular receptor moieties for the adhesin AIDA-I have not been identified. Here, it is demonstrated that the purified adhesin binds specifically to a high-affinity class of receptors on HeLa cells. Additionally, the adhesin was found to bind to a variety of mammalian cell types, indicating a broad tissue distribution of the receptor moiety. By using complementary techniques, including co-immunoprecipitation and one- and two-dimensional gel electrophoresis, the AIDA-I binding protein on HeLa cells was identified as a surface glycoprotein of about 119 kDa (gp119). The gp119 AIDA-I cellular receptor protein was characterized biochemically and found to be an integral N-glycosylated membrane protein with a pI of 5·2.
-
-
-
Haemagglutinin/protease expression and mucin gel penetration in El Tor biotype Vibrio cholerae
More LessVibrio cholerae of both biotypes produce a soluble Zn2+-dependent metalloprotease: haemagglutinin/protease (Hap), encoded by hapA. Hap has been shown to have mucinolytic and cytotoxic activity. These activities are likely to play an important role in the pathogenesis of cholera and the reactogenicity of attenuated vaccine strains. Production of Hap requires transcriptional activation by the HapR regulator and is repressed by glucose. The present study shows that mucin purified from two sources, bile salts, and growth at 37 °C enhanced Hap protease production. Analysis of hapA and hapR promoter fusions with the lacZ gene showed both promoters to be activated in a cell-density-dependent pattern. Glucose repressed and mucin induced the hapA promoter by a HapR-independent mechanism. Bile had no effect on either hapR or hapA promoter activity. Expression of hapA was required for vibrios to translocate through a mucin-containing gel. These results suggest Hap to play an important role in cholera pathogenesis by promoting mucin gel penetration, detachment and spreading of infection along the gastrointestinal tract.
-
-
-
EST analysis of genes expressed by the zygomycete pathogen Conidiobolus coronatus during growth on insect cuticle
More LessConidiobolus coronatus (Zygomycota) is a facultative saprobe that is a pathogen of many insect species. Almost 2000 expressed sequence tag (EST) cDNA clones were sequenced to analyse gene expression during growth on insect cuticle. Sixty percent of the ESTs that could be clustered into functional groups (E⩽10−5) had their best blast hits among fungal sequences. These included chitinases and multiple subtilisins, trypsin, metalloprotease and aspartyl protease activities with the potential to degrade host tissues and disable anti-microbial peptides. Otherwise, compared to the ascomycete entomopathogen Metarhizium anisopliae, Con. coronatus produced many fewer types of hydrolases (e.g. no phospholipases), antimicrobial agents, toxic secondary metabolites and no ESTs with putative roles in the generation of antibiotics. Instead, Con. coronatus produced a much higher proportion of ESTs encoding ribosomal proteins and enzymes of intermediate metabolism that facilitate its rapid growth. These results are consistent with Con. coronatus having adapted a modification of the saprophytic ruderal-selected strategy, using rapid growth to overwhelm the host and exploit the cadaver before competitors overrun it. This strategy does not preclude specialization to pathogenicity, as Con. coronatus produces the greatest complexity of proteases on insect cuticle, indicating an ability to respond to conditions in the cuticle.
-
-
-
Helicobacter pylori tissue tropism: mouse-colonizing strains can target different gastric niches
Studies with the mouse-adapted Helicobacter pylori strain SS1 had supported an idea that infections by this pathogen start in the gastric antrum and spread to the corpus after extensive mucosal damage. This paper shows that the unrelated strain X47 colonizes the corpus preferentially. Differences between strains in preferred gastric region were detected by co-inoculating mice with a mixture of SS1 and X47, and genotyping H. pylori recovered after 2–8 weeks of infection by vacA s allele PCR and RAPD fingerprinting. Mixed infections were found in each of 59 co-inoculated young C57BL/6J mice. On average, however, SS1 was fourfold more abundant than X47 in the antrum and X47 was threefold more abundant than SS1 in the corpus. Similar results were obtained in mice inoculated first with one strain and then the other strain 2 weeks later. SS1 was even more abundant in the antrum of elderly (>1 year old) mice (97 % of isolates). Qualitatively similar SS1 and X47 tissue distributions were seen using unrelated mouse lines (AKR/J, A/J, DBA/2J, BALB/cJ, LG/J, SM/J), but with significantly different SS1 : X47 ratios in some cases. These results suggest the existence of at least two distinct gastric niches whose characteristics may be affected by host genotype and age (physiology), and indicate that strains differ in how effectively they colonize each niche. Differences among gastric regions and the mixed infections that these allow may contribute to H. pylori diversity and genome evolution.
-
- Physiology
-
-
-
Incorporation of iron into Tritrichomonas foetus cell compartments reveals ferredoxin as a major iron-binding protein in hydrogenosomes
The intracellular transport of iron and its incorporation into organelles are poorly understood processes in eukaryotes and virtually unknown in parasitic protists. The transport of iron is of particular interest in trichomonads, which possess hydrogenosomes instead of mitochondria. The metabolic functions of hydrogenosomes, which contain a specific set of FeS proteins, entirely depend on iron acquisition. In this work the incorporation of iron into the cattle parasite Tritrichomonas foetus was monitored. Iron was efficiently taken up from 59Fe-nitrilotriacetic acid and accumulated in the cytosol (88·9 %) and hydrogenosomes (4·7 % of the total radioactivity). Using atomic absorption spectrophotometry, an unusually high steady-state iron concentration in hydrogenosomes was determined [54·4±1·1 nmol Fe (mg protein)−1]. The concentration of iron in the cytosol was 13·4±0·5 nmol Fe (mg protein)−1. Qualitative analysis of incorporated iron was performed using native gradient PAGE. The majority of the 59Fe in the cytosol appeared as the labile-iron pool, which represents weakly bound iron associated with compounds of molecular mass ranging from 5000 to 30 000 Da. Ferritin was not observed in Tt. foetus, nor in two other anaerobic protists, Entamoeba histolytica and Giardia intestinalis. Analysis of Tt. foetus hydrogenosomes showed at least nine iron-binding compounds, which were absent in metronidazole-resistant mutants. The major iron-binding compound was identified as [2Fe–2S] ferredoxin of the adrenodoxin type.
-
-
-
-
Signal-mediated cross-talk regulates stress adaptation in Vibrio species
More LessQuorum sensing systems serve as a means of ‘census taking’ of conspecific and non-conspecific bacteria in the near vicinity. The acylated homoserine lactone (AHL) quorum sensing system has been proposed to be primarily an intra-specific communication system, while the AI-2 autoinducer signalling system is proposed to be an interspecific communication system. Here it is shown that AI-2-like signalling in two marine Vibrio species, Vibrio vulnificus and ‘Vibrio angustum’ S14, induces the core response phenotypes of starvation adaptation and stress resistance, and that a signal antagonist can competitively inhibit these phenotypes. Furthermore, the signals produced by a range of Vibrio species have the ability to induce these phenotypes in V. vulnificus and ‘V. angustum’ S14, indicating that, at least in Vibrio species, AI-2-like signalling systems function as interspecies communication systems capable of ‘cross-talk’ and of regulating environmentally relevant phenotypes.
-
-
-
Transcriptional, translational and metabolic regulation of glycolysis in Lactococcus lactis subsp. cremoris MG 1363 grown in continuous acidic cultures
More LessThe physiological behaviour of Lactococcus lactis subsp. cremoris MG 1363 was characterized in continuous culture under various acidic conditions (pH 4·7–6·6). Biomass yield was diminished in cultures with low pH and the energy dedicated to maintenance increased due to organic acid inhibition and cytoplasmic acidification. Under such acidic conditions, the specific rate of glucose consumption by the bacterium increased, thereby enhancing energy supply. This acceleration of glycolysis was regulated by both an increase in the concentrations of glycolytic enzymes (hierarchical regulation) and the specific modulation of enzyme activities (metabolic regulation). However, when the inhibitory effect of intracellular pH on enzyme activity was taken into account in the model of regulation, metabolite regulation was shown to be the dominant factor controlling pathway flux. The changes in glycolytic enzyme concentrations were not correlated directly to modifications in transcript concentrations. Analyses of the relative contribution of the phenomena controlling enzyme synthesis indicated that translational regulation had a major influence compared to transcriptional regulation. An increase in the translation efficiency was accompanied by an important decrease of total cellular RNA concentrations, confirming that the translation apparatus of L. lactis was optimized under acid stress conditions.
-
-
-
Budding of melanized Cryptococcus neoformans in the presence or absence of l-dopa
More LessCryptococcus neoformans is a pathogenic fungus that produces melanin when incubated in the presence of certain phenolic substrates such as l-3,4-dihydroxyphenylalanine (l-dopa). Melanin is an enigmatic polymer that is deposited in the cell wall and contributes to virulence. Substantial progress has been made in understanding the synthesis of melanin and the mechanisms by which it contributes to virulence, but relatively little is known about how melanin is rearranged during growth and budding. In this study we used transmission and scanning electron microscopy and immunofluorescence of melanized cells and melanin ‘ghosts' to study the process of melanization during replication. Budding in melanized C. neoformans results in focal disruption of cell-wall melanin at the bud site. In the presence of l-dopa, bud-related melanin defects are repaired and daughter cells are melanized. However, in the absence of substrate, mother cells cannot repair their melanin defects and daughter cells are non-melanized. Hence, melanin in the parent cell is not carried to the daughter cells, but rather is synthesized de novo in buds. These results imply that melanin remodelling occurs during cell growth in a process that involves degradation and synthesis at sites of budding.
-
- Plant-Microbe Interactions
-
-
-
A purL mutant of Sinorhizobium fredii HH103 is symbiotically defective and altered in its lipopolysaccharide
The pleiotropic phenotype of an auxotrophic purL mutant (SVQ295) of Sinorhizobium fredii HH103 has been investigated. SVQ295 forms colonies that are translucent, produce more slime and absorb less Congo red than those of wild-type strain HH103. SVQ295 did not grow in minimal medium unless the culture was supplemented with thiamin and adenine or with thiamin and AICA-riboside (5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside), an intermediate of purine biosynthesis. Bacterial cultures supplemented with AICA-riboside or adenine reached the same culture density, although the doubling time of SVQ295 cultures containing AICA-riboside was clearly longer. S. fredii SVQ295 induced pseudonodules on Glycine max and failed to nodulate six different legumes. On Glycyrrhiza uralensis, however, nodules showing nitrogenase activity and containing infected plant cells were formed. SVQ295 showed auto-agglutination when grown in liquid TY medium and its lipopolysaccharide (LPS) electrophoretic profile differed from that of its parental strain HH103-1. In addition, four monoclonal antibodies that recognize the LPS of S. fredii HH103 failed to recognize the LPS produced by SVQ295. In contrast, 1H-NMR spectra of K-antigen capsular polysaccharides (KPS) produced by SVQ295 and the wild-type strain HH103 were similar. Co-inoculation of soybean plants with SVQ295 and SVQ116 (a nodA mutant derivative of HH103) produced nitrogen-fixing nodules that were only occupied by SVQ116.
-
-
Volumes and issues
-
Volume 170 (2024)
-
Volume 169 (2023)
-
Volume 168 (2022)
-
Volume 167 (2021)
-
Volume 166 (2020)
-
Volume 165 (2019)
-
Volume 164 (2018)
-
Volume 163 (2017)
-
Volume 162 (2016)
-
Volume 161 (2015)
-
Volume 160 (2014)
-
Volume 159 (2013)
-
Volume 158 (2012)
-
Volume 157 (2011)
-
Volume 156 (2010)
-
Volume 155 (2009)
-
Volume 154 (2008)
-
Volume 153 (2007)
-
Volume 152 (2006)
-
Volume 151 (2005)
-
Volume 150 (2004)
-
Volume 149 (2003)
-
Volume 148 (2002)
-
Volume 147 (2001)
-
Volume 146 (2000)
-
Volume 145 (1999)
-
Volume 144 (1998)
-
Volume 143 (1997)
-
Volume 142 (1996)
-
Volume 141 (1995)
-
Volume 140 (1994)
-
Volume 139 (1993)
-
Volume 138 (1992)
-
Volume 137 (1991)
-
Volume 136 (1990)
-
Volume 135 (1989)
-
Volume 134 (1988)
-
Volume 133 (1987)
-
Volume 132 (1986)
-
Volume 131 (1985)
-
Volume 130 (1984)
-
Volume 129 (1983)
-
Volume 128 (1982)
-
Volume 127 (1981)
-
Volume 126 (1981)
-
Volume 125 (1981)
-
Volume 124 (1981)
-
Volume 123 (1981)
-
Volume 122 (1981)
-
Volume 121 (1980)
-
Volume 120 (1980)
-
Volume 119 (1980)
-
Volume 118 (1980)
-
Volume 117 (1980)
-
Volume 116 (1980)
-
Volume 115 (1979)
-
Volume 114 (1979)
-
Volume 113 (1979)
-
Volume 112 (1979)
-
Volume 111 (1979)
-
Volume 110 (1979)
-
Volume 109 (1978)
-
Volume 108 (1978)
-
Volume 107 (1978)
-
Volume 106 (1978)
-
Volume 105 (1978)
-
Volume 104 (1978)
-
Volume 103 (1977)
-
Volume 102 (1977)
-
Volume 101 (1977)
-
Volume 100 (1977)
-
Volume 99 (1977)
-
Volume 98 (1977)
-
Volume 97 (1976)
-
Volume 96 (1976)
-
Volume 95 (1976)
-
Volume 94 (1976)
-
Volume 93 (1976)
-
Volume 92 (1976)
-
Volume 91 (1975)
-
Volume 90 (1975)
-
Volume 89 (1975)
-
Volume 88 (1975)
-
Volume 87 (1975)
-
Volume 86 (1975)
-
Volume 85 (1974)
-
Volume 84 (1974)
-
Volume 83 (1974)
-
Volume 82 (1974)
-
Volume 81 (1974)
-
Volume 80 (1974)
-
Volume 79 (1973)
-
Volume 78 (1973)
-
Volume 77 (1973)
-
Volume 76 (1973)
-
Volume 75 (1973)
-
Volume 74 (1973)
-
Volume 73 (1972)
-
Volume 72 (1972)
-
Volume 71 (1972)
-
Volume 70 (1972)
-
Volume 69 (1971)
-
Volume 68 (1971)
-
Volume 67 (1971)
-
Volume 66 (1971)
-
Volume 65 (1971)
-
Volume 64 (1970)
-
Volume 63 (1970)
-
Volume 62 (1970)
-
Volume 61 (1970)
-
Volume 60 (1970)
-
Volume 59 (1969)
-
Volume 58 (1969)
-
Volume 57 (1969)
-
Volume 56 (1969)
-
Volume 55 (1969)
-
Volume 54 (1968)
-
Volume 53 (1968)
-
Volume 52 (1968)
-
Volume 51 (1968)
-
Volume 50 (1968)
-
Volume 49 (1967)
-
Volume 48 (1967)
-
Volume 47 (1967)
-
Volume 46 (1967)
-
Volume 45 (1966)
-
Volume 44 (1966)
-
Volume 43 (1966)
-
Volume 42 (1966)
-
Volume 41 (1965)
-
Volume 40 (1965)
-
Volume 39 (1965)
-
Volume 38 (1965)
-
Volume 37 (1964)
-
Volume 36 (1964)
-
Volume 35 (1964)
-
Volume 34 (1964)
-
Volume 33 (1963)
-
Volume 32 (1963)
-
Volume 31 (1963)
-
Volume 30 (1963)
-
Volume 29 (1962)
-
Volume 28 (1962)
-
Volume 27 (1962)
-
Volume 26 (1961)
-
Volume 25 (1961)
-
Volume 24 (1961)
-
Volume 23 (1960)
-
Volume 22 (1960)
-
Volume 21 (1959)
-
Volume 20 (1959)
-
Volume 19 (1958)
-
Volume 18 (1958)
-
Volume 17 (1957)
-
Volume 16 (1957)
-
Volume 15 (1956)
-
Volume 14 (1956)
-
Volume 13 (1955)
-
Volume 12 (1955)
-
Volume 11 (1954)
-
Volume 10 (1954)
-
Volume 9 (1953)
-
Volume 8 (1953)
-
Volume 7 (1952)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)