- Volume 134, Issue 1, 1988
Volume 134, Issue 1, 1988
- Biochemistry
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Purification and Characterization of the Isopenicillin N Synthase of Streptomyces lactamdurans
More LessThe isopenicillin N synthase (cyclase) of Streptomyces lactamdurans (syn. Nocardia lactamdurans) has been purified to near homogeneity as judged by SDS-PAGE and isoelectric focusing. This enzyme catalyses the oxidative cyclization of the tripeptide δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine to isopenicillin N. The enzyme required DTT, Fe2+ and oxygen and it was greatly stimulated by ascorbic acid. It was strongly inhibited by Co2+, Zn2+ and Mn2+. Optimal pH and temperature were 7·0 and 25 °C (with the assay conditions used), respectively. The apparent K m of isopenicillin N synthase for δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine was 0·18 mm. The enzyme is a monomer with an M r of 26500 ± 1000 and a pI of 6.55.
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Purification and Properties of E-Caprolactone Hydrolases from Acinetobacter NCIB 9871 and Nocardia globerula CL1
More LessThe ε-caprolactone hydrolases (EC 3.1.1-) induced by growth of Acinetobacter NCIB 9871 and Nocardia globerula CL1 with cyclohexanol were purified to homogeneity. Both enzymes constituted approximately 1% of the soluble protein of the bacteria. Each was formed from two electrophoretically indistinguishable subunits and each had a closely similar M r value (≈60000). Both enzymes had high turnover numbers typical of carboxyesterases, broad pH-activity spectra and very restricted substrate specificities. In contrast to other bacterial lactone hydrolases they catalysed irreversible lactone hydrolysis and were not inhibited by thiol-reactive compounds. Their sensitivity to Paraoxon (diethyl p-nitrophenylphosphate) suggested that they, in common with mammalian acetylcholinesterase and carboxyesterases, have a functional catalytic centre serine.
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Plant and Bacterial Chitinases Differ in Antifungal Activity
More LessChitinases were isolated from the grains of wheat, barley and maize, and compared with those obtained from Serratia marcescens, Streptomyces griseus and Pseudomonas stutzeri for antifungal activity and enzyme specificity. The six enzymes were tested for antifungal activity using an assay based upon inhibition of hyphal extension of the fungi Trichoderma reesei and Phycomyces blakesleeanus. Antifungal activity was observed with as little as 1 μg of each of the grain chitinases, whereas none of the bacterial chitinases had any effect on hyphal extension, even at 50 #x03BC;g chitinase per assay. This difference in antifungal activity correlated with the different mechanisms of action of the two classes of enzymes. In common with other plant chitinases, the grain chitinases functioned as endochitinases and contained lysozyme activity. In contrast, the bacterial enzymes were exochitinases and hydrolysed the chromogenic trisaccharide analogue p-nitrophenyl-β-D-N, N′-diacetylchitobiose, which proved to be an excellent substrate for assaying bacterial chitinases. These experiments strengthen the hypothesis that plant chitinases function to protect the host against fungal infections.
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Cellular Fatty Acid Composition of Deleya halophila: Effect of Growth Temperature and Salt Concentration
The cellular fatty acid composition of Deleya halophila, a moderately halophilic bacterium, grown at different temperatures and NaCl concentrations is reported. When the temperature was lowered the amounts of monounsaturated C16:1 and C18:1 fatty acids increased with a corresponding decrease in the amounts of saturated C16:0 and C18:0 fatty acids. Increasing the salt concentration in the medium resulted in an increase of cyclopropane fatty acids, with a concomitant decrease in the monounsaturated fatty acids, suggesting that cyclopropane synthetase is activated or induced by high levels of salt.
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Polar Lipids and Glycine Betaine from Haloalkaliphilic Archaebacteria
More LessThe major polar lipids from haloalkaliphilic archaebacteria of the genera Natronobacterium and Natronococcus have been analysed by spectroscopic methods, including 13C NMR, to establish unequivocal structural detail. Diether forms of phosphatidylglycerol (PG) and phosphatidyl-glycerophosphate (PGP) are the major polar lipids; PGP is the main component for all species. Natronobacterium spp. show a preponderance of the 2-O-sesterterpanyl-3-O-phytanyl glycerol diether form (C25, C20) of both PG and PGP, whereas Natronococcus occultus has a preponderance of the diphytanylglycerol diether form (C20, C20) for both. In all cases, PGP (C25, C20 and C20, C20 forms) eluted from silica columns in association with glycine betaine (trimethylglycine).
5 May 1987
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Biological and Biochemical Characterization of Novel Lipid-like Antibacterial substances (Mutalipocins) Produced by Streptococcus mutans Strain 32K
More LessTwo novel antibacterial substances (designated mutalipocins) have been isolated from the culture supernatant of Streptococcus mutans strain 32K (serotype c). The mutalipocins were purified by extraction of the culture supernatant with light petroleum (b.p. range 30舑60 ŶC), followed by Lobar column chromatography on Lichroprep RP-8. HPLC indicated that both mutalipocin preparations (ML-I and ML-II) were homogeneous. The M r values of ML-I and ML-II were less than 1000. Both mutalipocins were unaffected by treatment over the pH range 3·0–10·0, or with phospholipase A or proteolytic enzymes, but were partially inactivated by treatment with lipase or phospholipase C. ML-II was resistant to heat treatment. TLC indicated that ML-I and ML-II contained unsaturated, aldehyde and/or ketone, and ester groups. The inhibition of S. mutans by ML-I and ML-II was due to bactericidal, rather than bacteriostatic, activities. The antibacterial spectra of ML-I and ML-II were narrower and more species-specific than those of bacteriocins produced by other Gram-positive bacteria.
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Influence of Oxygen Tension on the Respiratory Activity of Mycobacterium phlei
More LessGrowth of Mycobacterium phlei under low oxygen tension resulted in specific activities two to twenty times lower for formate dehydrogenase, malate dehydrogenase, -hydroxybutyrate dehydrogenase, lactate oxidase and NADH dehydrogenase than when cultures were grown under high aeration. An increase in fumarate reductase and succinate dehydrogenase occurred with M. phlei grown under low oxygen tension. Malate: vitamin K dehydrogenase and glucose-6-phosphate dehydrogenase activity were not significantly affected by the oxygen tension used to grow the bacteria, and neither culture contained a lactate dehydrogenase. With growth of M. phlei in conditions of low oxygen tension, cytochrome a was not detected, but cytochrome b was prominent in membranes and cytochrome c was present in the soluble fraction
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- Development And Structure
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Penetrating Structures of Anaerobic Rumen Fungi in Cattle and Swamp Buffalo
More LessRhizoids of anaerobic fungi colonizing fragments of guinea grass and rice straw in the rumen of cattle and swamp buffalo produced appressorium-like structures for penetration of the plant cell walls. These structures were generally lobed vesicles with fine penetration pegs, which penetrated through the cell wall and then expanded and continued their growth in adjacent cells, forming normal rhizoids which would in turn produce more ‘appressoria’ for penetration of the next cell. Their size and form varied with the size of the cell in which they developed. Small, flat ‘appressoria’ were produced in cells with small lumina while bigger and longer ‘appressoria’ developed in larger cells. ‘Appressoria’ were clearly observed in rhizoids of fungi colonizing the plant fragments about 1 h after incubation in the rumen and were produced in rumen fungi with spherical, oval or ovoid sporangia.
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- Genetics And Molecular Biology
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Characterization of the Conjugation System Associated with the Staphylococcus aureus Plasmid pJE1
More LessThe conjugation system of Staphylococcus aureus that is conferred, at least in part, by plasmid pJE1, requires cell-to-cell contact. Optimum transfer was found when the numbers of donor and recipient cells were equal. Certain antibiotics increased the conjugation frequency. Fragments of plasmid pJE1 were cloned into a staphylococcal plasmid vector; although separate clones were isolated that conferred ethidium bromide resistance and gentamicin resistance, none of the clones carried the ability to conjugate. Transposon mutagenesis with Tn551 was used to create 26 mutants of pJE1. These were analysed for the position of the insertion and for their ability to conjugate. The sites of insertion were non-random. Only six mutants were unaffected in their conjugability; one showed increased ability to conjugate whilst the rest were either unable to conjugate or showed a reduced frequency. It is concluded that there are at least two separate regions necessary for conjugation and that the system is not obviously similar to that reported in streptococci.
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Phenotypic and Genetic Characterization of Mutations in the spoIVC Locus of Bacillus subtilis
More LessThe spoIVC locus of Bacillus subtilis was analysed. Fourteen spoIVC mutants isolated following nitrosoguanidine mutagenesis were used along with two previously characterized spoIVC mutants to construct a fine structure genetic map of the locus. The recombination index (RI) measured between extreme mutations was 0·26; no recombination could be detected between four of the mutations. Complementation analysis showed that all the mutations fall into two cistrons. The RI between extreme mutations in cistron A was about 0·17 and that between extreme mutations in cistron B was about 0·05. In respect of biochemical markers, the spoIVC mutations all produced similar phenotypes, irrespective of their location. However, in both cistrons oligosporogenous and asporogenous mutations mapped close together.
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Designed Gene Amplification on the Bacillus subtilis Chromosome
More LessWe previously reported the cloning of a 1·6 kb HindIII fragment (containing the junction of the repeating unit) from chromosomal DNA of Bacillus subtilis strain B7 in which tandem amplification of a 16 kb region occurred, and the induction of B7-type gene amplification by competence transformation with this cloned fragment. Based on this result, we designed, on the B. subtilis chromosome, a gene amplification of the 22 kb repeating unit containing the a-amylase structural gene (amyE), the tunicamycin-resistance gene (tmrB) and the shikimate kinase structural gene (aroI). We cloned only two short DNA fragments from both termini of the 22 kb region, constructed a junction structure of the designed repeating unit on pBR327 and transformed a B. subtilis wild-type strain by this constructed plasmid. As a result, we succeeded in obtaining tunicamycin-resistant (Tmr) transformants in which the designed gene amplification of 22 kb occurred on the chromosome. The Tmr transformants showed high productivity of α-amylase and shikimate kinase. The copy number of the repeating unit was estimated to be 10–20. This system may provide an effective means of amplifying long (> 20 kb) DNA regions on the chromosome.
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Molecular Cloning and Nucleotide Sequence of the Cyclomaltodextrin Glucanotransferase Gene from the Alkalophilic Bacillus sp. Strain No. 38-2
More LessThe cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) gene from the alkalophilic Bacillus sp. strain no. 38-2 was cloned in Escherichia coli using pBR322. A plasmid, pCS8, was isolated from a transformant producing CGTase and the cloned CGTase gene was found to be in a 5·3 kb DNA fragment. The nucleotide sequence of a 2·5 kb segment encoding the CGTase was determined. This segment showed an open reading frame which would encode a polypeptide of 712 amino acids. The pCS8 CGTase had the same enzymic properties as those of the extracellular CGTase produced by the alkalophilic Bacillus sp. strain no. 38-2. The nucleotide and amino acid sequences of this CGTase gene and gene product, respectively, have strong homology with those of the Bacillus macerans CGTase.
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Highly Efficient Genetic Transformation of Bacillus subtilis Attached to Sand Grains
More LessGenetic transformation at the solid/liquid interface was studied using Bacillus subtilis 1G20 (trpC2) with a flow-through system of columns filled with chemically pure sea sand. Studies were done at 23 °C. In one type of experiment, competent cultures were incubated with sand-adsorbed DNA, and in another, competent cultures were exposed to sand and then incubated with dissolved DNA for transformation. Of the applied cells, around 10% were retained in columns filled with DNA-loaded sand and around 1% in columns with pure sand. Reversible attachment of some of the cells to surfaces of sand grains could be demonstrated. The overall transformation frequencies obtained were 25- to 50-fold higher than in a standard liquid culture procedure. In this standard procedure, transformation was sensitive to DNAase I concentrations above 50 ng ml−1, whereas in sand columns it was resistant to DNAase I concentrations up to 1 g ml−1. Quantification of transformants eluting from columns indicated that sand-attached cells detach at some point after DNA binding or uptake.
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Distribution of Insertion Sequence ISRm1 in Rhizobium meliloti and Other Gram-negative Bacteria
More LessAn internal 0·9 kb segment of Rhizobium meliloti insertion sequence ISRm1 was used as a probe to determine the distribution of ISRm1 in strains of R. meliloti and other Gram-negative bacteria. The insertion sequence was detected in 80% (12/15) of R. meliloti strains from different parts of the world. Its copy number ranged from one to at least eleven. The ISRm1 copies detected showed variation in their internal restriction sites and their degree of homology to the probe. ISRm1 was found in a variety of genomic restriction fragments, and was detected in plasmids, including the nod and exo megaplasmids of R. meliloti. Other rhizobia found to contain ISRm1 were a strain of R. leguminosarum biovar phaseoli and two Rhizobium isolates capable of nodulating both Medicago sativa and Phaseolus vulgaris. It was also found in a diazotrophic soil bacterium isolated from the roots of wetland rice.
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Comparative Complementation Mapping of Methylophilus spp. Using Cosmid Gene Libraries and Prime Plasmids
More LessCosmid gene libraries of the obligate methylotrophs Methylophilus viscogenes and Methylophilus methylotrophus AS1 were generated by ligating Sau3A partial digests of chromosomal DNA into the broad-host-range cosmid vector pLA2917. Genetic linkage groups were identified for each organism by complementation following mobilization of the recombinant cosmids to a wide range of Pseudomonas aeruginosa and Escherichia coli auxotrophs. The linkage data thus obtained confirmed and extended those previously established by prime plasmid complementation, and the two methylotrophs showed very similar arrangements for four of the gene clusters studied. However, comparison of DNA sequences which complemented the same auxotrophic markers failed to demonstrate restriction fragment identity or substantial DNA-DNA homology between the two methylotrophs.
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- Pathogenicity And Medical Microbiology
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Alginate Inhibition of the Uptake of Pseudomonas aeruginosa by Macrophages
More LessPseudomonas aeruginosa alginate was purified and characterized in terms of uronic acid, carbohydrate and protein content, as well as by infra-red spectroscopy and gel electrophoresis. Added exogenous bacterial alginate inhibited the uptake and degradation of both viable and non-viable radiolabelled non-mucoid P. aeruginosa by resident mouse peritoneal macrophages. Alginic acid (from seaweed) inhibited the same parameters to almost the same degree. Bacterial alginate also inhibited the uptake of fluorescent-labelled zymosan and latex particles. Starch, at equivalent viscosity to the alginate, inhibited the uptake and degradation of radiolabelled nonviable P. aeruginosa to a greater extent, but Dextran T500 had no effect. This suggests that the viscous nature of alginate exerts a non-specific inhibitory effect on the uptake and subsequent degradation of phagocytosible particles.
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Gamma Interferon Enhances the Killing of Staphylococcus aureus by Human Neutrophils
More LessThe effect of purified human interferon-? on the responsiveness of human neutrophils was investigated. Pre-incubation of neutrophils with 100 U interferon ml-1 for 10 min at 37C resulted in a 2.5-fold increase in N-formylmethionyl-leucyl-phenylalanine-stimulated reactive oxygen metabolite generation (as assayed by luminol-dependent chemiluminescence). Pretreatment of neutrophils with interferon also potentiated their ability to kill Staphylococcus aureus, and thus it is proposed that this lymphokine may also enhance neutrophil function in vivo under certain pathological conditions.
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Flagella, Motility and Invasive Virulence of Pseudomonas aeruginosa
More LessThe role of motility as a virulence factor in Pseudomonas aeruginosa burn wound sepsis was examined using mutants deficient in the Fla or Mot phenotype. Physiological profiles of parental strains and Fla- and Mot- mutants were similar with respect to antibiograms, O antigen types, growth rates, and proteolytic, exotoxin A and phospholipase activities, providing evidence for isogenicity. Lethality studies using a subcutaneous mouse burn model showed that three Fla- mutants and one Mot- mutant were much less virulent (102 to 105 times) than the parent wild-type. Topical challenges in the flame burn model showed that a Fla- mutant of strain M-2 was approximately tenfold less virulent. A reduction in virulence, although somewhat less than tenfold, was also observed in the scald burn model for M-2 Fla-, and Mot- strains. Tissue colonization experiments revealed a characteristic, rapidly systemic infection in burned mice challenged with wild-type organisms. Nonmotile mutants similarly proliferated in the burn wound, but the characteristic bacteraemia and systemic invasion were markedly absent. The infection remained localized in the skin wound and the mice survived. The pattern of infection by nonmotile mutants in the colonization studies was very similar to that obtained with Fla+ cells in burned animals passively treated with antiflagellar antibody. These results add substantial support to the concept of motility as a P. aeruginosa virulence factor in invasive infections.
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Molecular Cloning and Expression of the Coagulase Gene of Staphylococcus aureus 8325-4
More LessThe gene coding for coagulase (coa) was cloned from Staphylococcus aureus 8325-4 in a λ replacement vector in Escherichia coli. Coagulase (plasma-clotting) activity was measured in λ coa lysates and an immunoreactive protein of 60 kDa was detected by Western immunoblotting with anti-coagulase serum. This protein comigrated with the major immunoreactive protein in supernatants of S. aureus 8325-4. The coa gene was subcloned in pUC vectors. One recombinant expressed a 60 kDa immunoreactive protein and plasma-clotting activity. A putative β-galactosidase-coagulase fusion protein and truncated peptides were expressed by variants formed by subcloning. These results are consistent with previously published biochemical data that the prothrombin-binding domain of coagulase is located in the N-terminus of the protein. The cloned coa gene was transferred into S. aureus on a shuttle plasmid. Expression of coagulase was higher in a strain with a mutation in the agr locus, which controls the level of several exoproteins in S. aureus, suggesting that agr normally regulates coagulase expression negatively.
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In vivo Production of a Tissue-destructive Protease by Legionella pneumophila in the Lungs of Experimentally Infected Guinea-pigs
More LessA tissue-destructive protease of Legionella pneumophila was assayed for in the lungs of experimentally infected guinea-pigs by ELISA. It was found in amounts equivalent to the known lethal dose of purified protease administered by the intranasal route. The identity of the protease was confirmed by immunoblot analysis. This is further evidence that Legionella pneumophila protease may play a major role in the pathogenesis of Legionnaires’ disease.
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Characteristics and Distribution of Extracellular Proteases from Aeromonas hydrophila
More LessThe major extracellular proteases of Aeromonas hydrophila NRC 505 and ATCC 7966 are a thermostable metallo-protease (TSMP) and a thermolabile serine-protease (TLSP), respectively. The purified enzymes differed in sensitivity to heating at 56 °C for 30 min, in response to the inhibitors EDTA and phenylmethylsulphonyl fluoride (PMSF), and were antigenically distinct. When crude extracellular products (ECP) of 47 strains of A. hydrophila were screened, 27 strains produced both TSMP and TLSP. TSMP was the only extracellular protease produced by 19 strains, whereas only A. hydrophila ATCC 7966 produced TLSP as its sole protease. This distribution of protease enzymes among strains explains conflicting reports from studies in which single strains of A. hydrophila were examined. The TLSP of A. hydrophila was similar to the protease of A. salmonicida. Either or both TSMP and TLSP were produced by some strains of A. sobria and A. caviae.
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- Physiology And Growth
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Studies on the Proteolytic Activity of Bacteroides fragilis
More LessThe proteolytic activity of the intestinal bacterium Bacteroides fragilis NCDO 2217 was cell-bound during exponential growth, but was progressively released from the cells in stationary phase. Proteins hydrolysed included casein, trypsin, chymotrypsin, azocasein and the proteins in azosoya bean flour. Collagen, azocoll, elastin, gelatin, ovalbumin and bovine serum albumin were either weakly degraded or completely refractory to proteolysis. Arylamidase activity was exhibited against leucine p-nitroanilide (LPNA), leucine β-naphthylamide, glycyl-proline p-nitroanilide and valyl-alanine p-nitroanilide. The bacterium grew with ammonia, peptone or casein as sole nitrogen source. Azocasein- and LPNA-hydrolysing activities were consistently higher when grown on casein. Cell-bound protease activity increased concomitantly with growth rate in both carbon- and nitrogen-limited continuous culture. Leucine arylamidase activity was also growth-rate-dependent, being 3-fold greater at D = 0·18 h−1 compared to D = 0·03 h−1. Extracellular proteolytic activity was only detected at low growth rates, accounting for about 25% of total protease activity.
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Photoassimilation of Fatty Acids, Fatty Alcohols and Sugars by Euglena gracilis Z
Assimilation of fatty acids, fatty alcohols and sugars by Euglena gracilis Z was investigated with or without illumination. Propionate, butyrate, valeriate, hexanoate, myristate, palmitate, ethanol, propanol, lauryl alcohol, tridecanol and myristyl alcohol supported considerable growth. The assimilation of propionate, valeriate, palmitate, butanol, lauryl alcohol and myristyl alcohol were strictly light-dependent. The photoassimilation of myristyl alcohol was saturated by lower light intensity than photosynthesis and was not completely inhibited by a photosynthetic inhibitor, suggesting involvement of a photoreaction other than photosynthesis in the photoassimilation. d-Glucose, D-fructose, D-galactose, d-xylose, D-glyceraldehyde and glycerol also supported growth. Disaccharides were not used as the carbon source for growth. The difference in the mechanism of photoassimilation between myristyl alcohol and D-galactose is discussed.
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Isolation of Pellicular Cobalamin-binding Proteins of the Cobalamin Uptake System of Euglena gracilis
More LessEuglena gracilis pellicle, separated by sucrose density gradient centrifugation, had a high cobalamin (Cb1) binding activity. Of the Cb1 binding protein 65% was solubilized from E. gracilis pellicle by using 0·1% SDS/2 m-urea and the residual 35% by using 1% (w/v) SDS. Both of the Cb1 binding protein fractions showed a broad pH dependence for the binding of Cb1. No evidence for the involvement of SH-groups or metal ions in Cb1 binding was obtained. The K s values for cyanocobalamin of the proteins solubilized with 0·1% SDS/2 m-urea and with 1% SDS were 0·22 and 0·19 nm, respectively. The M r of a Cb1 binding polypeptide of each protein was estimated to be 38000 by SDS-PAGE. The Cb1 binding protein solubilized with 0·1% SDS/2 m-urea was purified to homogeneity. Inhibition experiments on Cb1 uptake in E. gracilis cells, using an antibody against the Cb1 binding protein solubilized with 0·1% SDS/2 m-urea, showed that the Cb1 binding proteins solubilized with 0·1% SDS/2 m-urea and 1% SDS take part in the slower secondary phase and in the initial rapid phase of Cb1 uptake in E. gracilis, respectively.
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Surface Colonization by and Life Cycle of Pelobacter acidigallici Studied in a Continuous-flow Microchamber
More LessCells of Pelobacter acidigallici strain WoGal grown in a continuous-flow microchamber with 0.1 mm-gallic acid as sole carbon source attached to the surface either irreversibly (nonmotile cells) or reversibly (motile cells). At low gallic acid concentrations (<0.1 mm) growth gave rise to microcolonies of < 128 cells which maintained their size by release of motile swarmer cells. Continuous biofilms were formed only at higher substrate concentrations (> 5 mm), at which both growth and cell deposition at the surface took place. Under starvation conditions, motile cells ceased to grow and were washed out, whereas irreversibly attached cells continued to divide but their daughter cells did not grow. The results suggest that this bacterium when growing at an attachment surface undergoes a complex life cycle including attachment and detachment processes and formation of motile swarmer cells.
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Aspects of Protease Production by Thermus Strain Ok6 and Other New Zealand Isolates
More LessThirteen strains of Thermus isolated from New Zealand hot pools were screened for their ability to grow on minimal or near-minimal media and to exhibit extracellular protease activity. Environmental regulation of protease production by one such strain, Thermus Ok6, was investigated in detail. Protease activity was maximally derepressed during growth under conditions which lead to energy starvation (i.e. highly oxidized carbon substrate, oxygen limitation, slow growth rate and a high external pH), and was variably repressed by different nitrogen sources. These results suggest that the function of the enzyme is to scavenge carbon/energy and nitrogen. The protease was loosely attached to the cell under these growth conditions but could be released by growing the organism in high concentrations of trypticase peptone plus yeast extract, by exposing the culture to moderate shear forces or by washing cells in high ionic strength solutions of various inorganic salts, organic acids or amino acids. A simple and rapid procedure for the partial purification of the enzyme is described.
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Nitrosamine Formation by Denitrifying and Non-denitrifying Bacteria: Implication of Nitrite Reductase and Nitrate Reductase in Nitrosation Catalysis
More LessBiochemical, microbiological and genetic studies were done to characterize the mechanism of bacterial formation of N-nitrosomorpholine (NMOR) from morpholine and nitrite at neutral pH. In Escherichia coli and Proteus morganii, the nitrosating activity was markedly induced when bacteria were cultured under anaerobiosis in minimal medium containing nitrate, while in the presence of nitrite there was no induction. However, induction of the nitrosating activity in Pseudomonas aeruginosa occurred in anaerobic cultures in the presence of either nitrate or nitrite. The nitrosation capacity was also examined in various E. coli K12 mutants whose structural gene of either nitrate reductase or nitrite reductase was deleted. Nitrosation was not linked to the three (NADH-, formate-and glucose-dependent) nitrite reductases but was directly dependent on the presence of a nitrate reductase.
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Control of Lipase Production by Rhizopus oligosporus under Various Growth Conditions
More LessSome factors influencing the growth and production of extracellular lipase by Rhizopus oligosporus were studied. Highest yields of enzyme were obtained when Tweens were the carbon source. Soybean meal extract supported good growth and enzyme production. Carbohydrates, vegetable oils, proteins or amino acids did not stimulate lipase production. The fungus grew well with carbohydrate-or protein-supplemented media but not with oils, unless emulsified with a non-metabolizable gum. The production of biomass in static cultures was maximum at 35–40 °C after 4 d at pH 5·5. The yield of lipase was maximum at 25 °C after 3 d at pH 6·5. Shaking cultures enhanced growth but decreased lipase production.
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Effects of Junlon and Hostacerin on the Electrokinetic Properties of Spores of Aspergillus niger, Phanerochaete chrysosporium and Geotrichum candidum
More LessThe electrophoretic behaviour of freshly harvested spores of Aspergillus niger, Phanerochaete chrysosporium and Geotrichum candidum was determined in solution at various pH values. Freshly harvested spores of all three species lacked positive mobility at low pH values, suggesting a preponderance of acidic surface groups. Spores of the ‘non-aggregating’ fungus, G. candidum, had a pH-mobility curve (peak of negative mobility between pH 3 and 4) which was quite different to those of spores of the ‘aggregating’ fungi, A. niger and P. chrysosporium. The pH-mobility curve of swollen spores of A. niger which had been incubated in medium differed from that of freshly harvested spores, suggesting that changes in the wall that occur during germination alter the electrophoretic properties of the spores; swollen spores of A. niger, unlike freshly harvested spores, had a negative mobility maximum at pH 5·0.
After treatment with Junlon-110 (a polyacrylic acid), spores of all three species had similar pH-mobility curves and all had peaks of negative mobility at pH 4·0. The electrophoretic mobility of spores of P. chrysosporium at pH 6·5 increased linearly with the concentration (0·01–0·4%, w/v) of Junlon used in the pre-treatment; electrophoretic mobility after pre-treatment with 0·005-0·1% (w/v) Hostacerin (sodium polyacrylate) increased only up to 0·01% (w/v) Hostacerin. The results obtained show that Junlon-110 and Hostacerin bind to fungal walls, and it is possible that spore and hyphal aggregation is reduced by these compounds because of repulsion between particles resulting from ionized carboxyl groups on the polymer.
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Carrot Phytoalexin Alters the Membrane Permeability of Candida albicans and Multilamellar Liposomes
More LessThe biochemical basis for the antimicrobial effect of the carrot phytoalexin 6-methoxymellein (6-MM) was examined. At fungistatic concentrations 6-MM retarded the ability of Candida albicans to incorporate radioactive thymidine, uridine and leucine into biopolymers. When C. albicans was incubated with 6-MM, 260-nm-absorbing materials and 3H-labelled compounds leaked from the cells. The inhibitory effects of 6-MM on cell growth and membrane functions were, however, reduced as the concentration of divalent metal cations added to the medium was increased. 6-MM interacted with multilamellar liposomes constituted from phosphatidylcholine, cholesterol and dicetyl phosphate, or from phosphatidylcholine only, resulting in the release of glucose trapped in these liposomes. These results suggest that 6-MM exerts its toxic effects on susceptible cells as a result of its interaction with their membranes and disturbance of membrane-associated functions.
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- Systematics
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Motility of Campylobacter jejuni in a Viscous Environment: Comparison with Conventional Rod-shaped Bacteria
More LessThe motility of four strains of Campylobacter jejuni in solutions of varying viscosity was measured and compared to that of a number of conventional rod-shaped bacteria (CRSB). All the bacteria tested showed an initial increase in velocity in the low viscosity solutions - between 1 and 3 centipoise (1 P = 0.1 Pa s). However, only the campylobacters were actively motile in highly viscous solutions with velocities ranging from 60 to 100 s-1. All strains of C. jejuni tested showed three separate peaks of motility as the viscosity of the solution was increased. A higher proportion of C. jejuni cells exhibited longer path lengths when the viscosity of the surrounding medium was increased from 1.4 to 57 cP. The findings of the study suggest that C. jejuni has a motility suited to movement in a viscous environment, and that this ability might provide the organism with an ecological advantage when in intestinal mucus. It is proposed that the mechanism of motility changes depending on the viscosity of the supporting environment.
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Volume 118 (1980)
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Volume 117 (1980)
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Volume 116 (1980)
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Volume 115 (1979)
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Volume 114 (1979)
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Volume 113 (1979)
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Volume 112 (1979)
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Volume 111 (1979)
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Volume 110 (1979)
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Volume 109 (1978)
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Volume 108 (1978)
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Volume 107 (1978)
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Volume 106 (1978)
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Volume 105 (1978)
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Volume 104 (1978)
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Volume 103 (1977)
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Volume 102 (1977)
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Volume 101 (1977)
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Volume 100 (1977)
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Volume 99 (1977)
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Volume 98 (1977)
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Volume 97 (1976)
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Volume 96 (1976)
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Volume 95 (1976)
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Volume 94 (1976)
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Volume 93 (1976)
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Volume 92 (1976)
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Volume 91 (1975)
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Volume 90 (1975)
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Volume 89 (1975)
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Volume 88 (1975)
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Volume 87 (1975)
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Volume 86 (1975)
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Volume 85 (1974)
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Volume 84 (1974)
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Volume 83 (1974)
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Volume 82 (1974)
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Volume 81 (1974)
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Volume 80 (1974)
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Volume 79 (1973)
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Volume 78 (1973)
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Volume 77 (1973)
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Volume 76 (1973)
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Volume 75 (1973)
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Volume 74 (1973)
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Volume 73 (1972)
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Volume 72 (1972)
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Volume 71 (1972)
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Volume 70 (1972)
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Volume 69 (1971)
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Volume 68 (1971)
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Volume 67 (1971)
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Volume 66 (1971)
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Volume 65 (1971)
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Volume 64 (1970)
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Volume 63 (1970)
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Volume 62 (1970)
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Volume 61 (1970)
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Volume 60 (1970)
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Volume 59 (1969)
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Volume 58 (1969)
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Volume 57 (1969)
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Volume 56 (1969)
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Volume 55 (1969)
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Volume 54 (1968)
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Volume 53 (1968)
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Volume 52 (1968)
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Volume 51 (1968)
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Volume 50 (1968)
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Volume 49 (1967)
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Volume 48 (1967)
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Volume 47 (1967)
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Volume 46 (1967)
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Volume 45 (1966)
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Volume 44 (1966)
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Volume 43 (1966)
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Volume 42 (1966)
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Volume 41 (1965)
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Volume 40 (1965)
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Volume 39 (1965)
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Volume 38 (1965)
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Volume 37 (1964)
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Volume 36 (1964)
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Volume 35 (1964)
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Volume 34 (1964)
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Volume 33 (1963)
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Volume 32 (1963)
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Volume 31 (1963)
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Volume 30 (1963)
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Volume 29 (1962)
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Volume 28 (1962)
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Volume 27 (1962)
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Volume 26 (1961)
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Volume 25 (1961)
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Volume 24 (1961)
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Volume 23 (1960)
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Volume 22 (1960)
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Volume 21 (1959)
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Volume 20 (1959)
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Volume 19 (1958)
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Volume 18 (1958)
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Volume 17 (1957)
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Volume 16 (1957)
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Volume 15 (1956)
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Volume 14 (1956)
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Volume 13 (1955)
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Volume 12 (1955)
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Volume 11 (1954)
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Volume 10 (1954)
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Volume 9 (1953)
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Volume 8 (1953)
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Volume 7 (1952)
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Volume 6 (1952)
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Volume 5 (1951)
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Volume 4 (1950)
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Volume 3 (1949)
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Volume 2 (1948)
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Volume 1 (1947)