- Volume 141, Issue 6, 1995
Volume 141, Issue 6, 1995
- Sgm Special Lecture
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- Biochemistry
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Hirsutellin A, a toxic protein produced in vitro by Hirsutella thompsonii
More LessA toxic protein, hirsutellin A, has been purified from the mite fungal pathogen, Hirsutella thompsonii, using ammonium sulphate precipitation, ion exchange chromatography and gel filtration on Bio-Gel P-10. The protein has been characterized as a monomer with a molecular mass of 15 kDa and an isoelectric point of 105. The amino acid composition and the N-terminal sequence of hirsutellin A (34 amino acids) have been determined. From these results, the toxin appears to be distinct from other known proteins. It is not glycosylated, and does not show proteolytic activity. The toxin is also antigenic, thermostable and not inactivated by treatments with proteolytic enzymes. Toxicity bioassays showed that injection of larvae of the waxmoth, Galleria mellonella, with hirsutellin A at low dosages [1 g toxin (g body wt)−1] caused a high mortality rate. Hirsutellin A was also toxic per os to neonatal larvae of the mosquito Aedes aegypti.
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A catalase from Streptomyces coelicolor A3(2)
More LessCatalase was purified from the Gram-positive bacterium Streptomyces coelicolor A3(2) in a three-step purification procedure comprising (NH4)2SO4, fractionation, Phenyl-Sepharose chromatography and Mono Q chromatography. The purification of catalase, as judged by the final specific activity of 110000 U mg-1 was 250-fold with a 35% yield. The native protein was a homotetramer with a subunit M r 55000. N-terminal and internal peptide sequence analyses showed that there was a high degree of sequence similarity between the S. coelicolor catalase and other microbial and mammalian catalases. Southern blot analysis indicated that there was a single catalase gene in S. coelicolor. The specific activity of catalase throughout the growth of batch cultures was investigated and elevated catalase activity was found in stationary-phase cells.
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Biosynthesis of fluorinated secondary metabolites by Streptomyces cattleya
More LessThe biosynthesis of organofluorine compounds by Streptomyces cattleya NRRL 8057 was examined using 19F NMR spectroscopy. The organism produced 12 mM fluoroacetate and 05 mM 4-fluorothreonine as secondary metabolites when cultured for 28 d on a chemically defined medium containing 2 mM fluoride. Cell suspensions from batch cultures harvested at the growth maximum of 4 d were not capable of fluoride uptake or fluorometabolite biosynthesis, but by 6 d had developed an efficient fluoride-uptake system and biosynthesized the two fluorometabolites in almost equal proportions. As the harvest age increased, the proportion of fluoroacetate to 4-fluorothreonine formed by cell suspensions rose progressively so that 16-d-old cells showed a ratio of 7626 for the two compounds. Fluoride uptake and fluorometabolite production by cell suspensions were highly dependent on pH, with both processes showing a maximum rate at pH 60 but declining rapidly at higher pH values. This decrease was particularly marked in the case of fluoroacetate biosynthesis which was barely detectable at pH 75. Fluoroacetate and 4-fluorothreonine showed only low levels of interconversion by cell suspensions, suggesting that the carbon skeleton of neither was derived by metabolism of the other. The limited interconversion observed is explicable in terms of a small degree of biological defluorination occurring with each compound, followed by reincorporation of the resulting fluoride ion into the organic form by the active fluorinating system, a phenomenon also noted on incubation of cell suspensions with a number of other fluorinated biochemical intermediates. Cell suspensions were supplemented with a variety of amino acids and tricarboxylic acid cycle intermediates to determine the identity of the carbon substrate of the fluorinating system. No compound tested significantly increased the total amount of fluorometabolites formed or altered their relative proportions. However, in studies with 14-labelled precursors, the highest level of incorporation into fluoroacetate by cell suspensions was recorded with [U-14C]glycolate, suggesting that this compound or an activated derivative may be the substrate for the fluorinating system in the biosynthesis of fluoroacetate.
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- Development And Structure
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Differential expression of genes under control of the mating-type genes in the secondary mycelium of Schizophyllum commune
More LessThe Schizophyllum commune SC3 gene, which encodes a hydrophobin that coats aerial hyphae, is expressed in both monokaryons and dikaryons. The dikaryons were formed by mating two monokaryons with different MATA and MATB genes, leading to activation of the MATA- and MATB-controlled pathways (MATA-on and MATB-on). In contrast to the monokaryons, the dikaryons also expressed other hydrophobin genes (SC1, SC4) as well as a gene (SC7) encoding a hydrophilic wall protein. None of these four genes was expressed in MATA-off MATB-on mycelia, indicating that MATB-on represses SC3 and that both MATA-on and MATB-on are required for activation of SC1, SC4 and SC7. In fruiting dikaryons, immunolabelling revealed that SC3p was produced by aerial hyphae but not by hyphae that constitute the fruit-body tissue. In contrast to aerial hyphae, the latter produced dikaryon-specific transcripts and secreted SC7p into the extracellular matrix of the tissue. This suggests that in the aerial hyphae of the dikaryon the MATB-on pathway was not effective (MATB-off). We observed that in these aerial hyphae the two nuclei were wider apart than in a typical dikaryon. Although other explanations are not ruled out, we tentatively propose that effective interaction of different MATB genes requires proximity of the two nuclei containing these genes, and that disruption of this binucleate state represents a novel mechanism of gene control for spatial cell differentiation in the secondary mycelium.
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Rhapidosomes from Aquaspirillum itersonii: disruption and subsequent renaturation and characterization of the component proteins
Rhapidosomes, tubular proteinaceous microstructures found in a variety of bacteria and algae, are resistant to disruption by many denaturing agents. They have potential application as a biomaterial and may also serve as a model for the study of self-assembly. Several reagents were tested for their ability to disrupt rhapidosomes isolated from Aquaspirillum itersonii into their component proteins. Only treatments with 01 M hydrochloric acid and 6 M guanidinium hydrochloride were found to disrupt rhapidosomes. A protocol was developed to renature the disrupted component proteins using rapid dilution and subsequent dialysis of the residual guanidinium hydrochloride. The renatured proteins were shown to have secondary structure as determined by circular dichroism. Furthermore, upon renaturation the two component proteins interacted with each other to form a complex of molecular mass > 2500 kDa. This complex, which may be a precursor in the pathway to rhapidosome formation, is currently being used to study the self-assembly process of these unique structures in vitro.
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- Genetics And Molecular Biology
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Neocallimastix frontalis enolase gene, enol: first report of an intron in an anaerobic fungus
R. Durand, M. Fischer, C. Rascle and M. FvreA DNA clone containing a putative enolase gene was isolated from a genomic DNA library of the anaerobic fungus Neocallimastix frontalis. It was deduced from sequence comparisons that the enolase gene was interrupted by a large 331 bp intron. The enolase gene, termed enol, has an ORF of 1308 bp and encodes a predicted 436 amino acid protein. The deduced amino acid sequence shows high identity (715-71%) to those of enolases from the yeasts Saccharomyces cerevisiae and Candida albicans. The G+ C content of the enolase coding sequence (438 mol%) is considerably higher than the G + C content of the intervening sequence (142 mol%) or the 5' and 3' non-translated flanking sequences (152 and 47 mol%, respectively). The codon usage of the N. frontalis enolase gene was very biased as has been found for the highly expressed genes of yeast and filamentous fungi. The gene has all the canonical features (polyadenylation signal, intron splicing boundaries) of genes isolated from aerobic filamentous fungi. Only one enolase gene could be detected in N. frontalis genomic DNA by Southern analysis with a homologous probe. RNA analysis detected a single enolase transcript of about 16 kb. When mycelium was grown on glucose, levels of enolase mRNA were markedly increased by comparison with enolase mRNA levels in mycelium grown on cellulose, suggesting that expression of the N. frontalis enolase gene was transcriptionally regulated by the carbon source.
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Derepression of the glyoxylate cycle in mutants of Neurospora crassa accelerated for growth on acetate
More LessTwo spontaneous allelic mutations have been isolated with the unusual semi-dominant phenotype of faster-than-wild-type growth on acetate as sole carbon source. The mutants were designated Aag-1 (accelerated acetate growth) and mapped on linkage group II. Upon re-isolation of both the Aag-1 alleles from repeated back-crosses to wild-type, between 1 and 6% of the progeny were found to be acu (acetate non-utilizing) mutants. Ten of these were selected for heterokaryon complementation analysis with known acu mutants; nine proved to be new alleles of acu-5 (deficient in acetyl-CoA synthetase), and one was a new acetate non-utilizing class, designated acu-14. Although the Aag-1 mutants clearly have no acetate-growth-related enzyme deficiencies, they did exhibit significant constitutive enzyme levels for acetyl-CoA synthetase and the glyoxylate cycle enzymes (isocitrate lyase and malate synthase) on the non-inducing carbon source, sucrose. The derepression was restricted to these enzymes, as representative enzymes from other carbon-assimilatory pathways remained repressed and subject to carbon catabolite repression. Northern blot analysis of the mRNA levels of acetyl-CoA synthetase and the glyoxylate cycle enzymes from the mutants demonstrated the derepression to occur at the level of transcription. These data suggest that the physiological explanation for the accelerated acetate growth phenotype lies in the standing levels of the acetate-assimilatory enzymes, which enable the mutants to forgo some of the normal time required for adaption to growth on acetate.
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Transcriptional and translational regulation of the expression of the major outer surface proteins in Lyme disease Borrelia strains
More LessThe major outer surface proteins of Lyme disease spirochaetes are differentially expressed in different isolates. Borrelia afzelii strain F1 expresses none, or very low amounts, of the OspA and OspB proteins. To elucidate the mechanisms that control the expression of these abundant surface proteins the ospAB operon of B. afzelii F1 was cloned, sequenced and compared to the previously sequenced ospAB operon of B. afzelii ACAI and Borrelia burgdorferi B31. The two B. afzelii strains showed almost 100% identity at the DNA level, although Coomassie-stained gels and Western blot analyses showed significant variation in the Osp protein content. Transcriptional analysis revealed that the amount of ospAB mRNA produced in B. afzelii F1 varies more than the amount of protein, suggesting that the expression of OspA and OspB proteins is regulated at both the transcriptional and the translational level. Furthermore, the inverse relationship between the transcription of ospC and the ospAB operon could indicate coregulation of these separately encoded operons.
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A gene from Renibacterium salmoninarum encoding a product which shows homology to bacterial zinc-metalloproteases
More LessA genomic library constructed from Renibacterium salmoninarum isolate MT444 DNA in the plasmid vector pBR328 was screened using Escherichia coli host strain DH1 for the expression of genes encoding putative virulence factors. A single haemolytic clone was isolated at 22 C and found to contain a 31 kb Hindlll fragment of inserted DNA. This fragment was present in seven isolates of R. salmoninarum which were examined. Western blots of extracts from clones exhibiting haemolytic activity were performed with antisera raised against either cellular or extracellular components of R. salmoninarum and failed to identify any additional proteins compared to control E. coli containing pBR328. However, minicell analysis revealed that a polypeptide with an apparent molecular mass of 65 kDa was associated with a haemolytic activity distinct from that previously described for R. salmoninarum. The nucleotide sequence of the gene encoding this product was determined and the amino acid sequence deduced. The product was 548 amino acids with a predicted molecular mass of 66757 Da and a pl of 557. The deduced amino acid sequence of the gene possessed strong similarities to those of a range of secreted bacterial zinc-metalloproteases and was tentatively designated hly. Neither protease nor lecithinase activities were detectable in E. coli recombinants expressing gene hly. Haemolytic activity was observed from 6 C to 37 C for erythrocytes from a number of mammalian species and also from fish. Gene hly was expressed in E. coli as a fusion protein consisting of maltose-binding protein at the N-terminus linked to all but the first 24 amino acids, largely constituting the putative signal peptide, of the N-terminus of Hly. The soluble fusion protein was produced and purified by affinity chromatography. Antiserum raised against the purified fusion protein was used to probe Western blots of cell lysates and extracellular products from seven isolates of R. salmoninarum cultured under conditions of iron-sufficiency or iron-restriction. The results indicate that the availability of iron modulates the expression of the hly gene.
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Nucleotide sequences of two fimbrial major subunit genes, pmpA and ucaA, from canine-uropathogenic Proteus mirabilis strains
More LessProteus mirabilis strains were isolated from dogs with urinary tract infection (UTI) and fimbriae were prepared from two strains. The N-terminal amino acid sequences of the major fimbrial subunits were determined and both sequences appeared identical to the N-terminal amino acid sequence of a urinary cell adhesin (UCA) (Wray, S. K., Hull, S. I., Cook, R. G., Barrish, J. Hull, R. A., 1986, Infect Immun 54, 43-49). The genes of two different major fimbrial subunits were cloned using oligonucleotide probes that were designed on the basis of the N-terminal UCA sequence. Nucleotide sequencing revealed the complete ucaA gene of 540 bp (from strain IVB247) encoding a polypeptide of 180 amino acids, including a 22 amino acid signal sequence peptide, and the pmpA (P. mirabilis P-like pili) gene of 549 bp (from strain IVB219) encoding a polypeptide of 183 amino acids, including a 23 amino acid signal sequence. Hybridization experiments gave clear indications of the presence of both kinds of fimbriae in many UTI-related canine P. mirabilis isolates. However, the presence of these fimbriae could not be demonstrated in P. vulgaris or other Proteus-related species. Database analysis of amino acid sequences of major subunit proteins revealed that the UcaA protein shares about 56% amino acid identity with the F17A and F111A major fimbrial subunits from bovine enterotoxigenic Escherichia coli. In turn, the PmpA protein more closely resembled the pyelonephritis-associated pili (Pap)-like major subunit protein from UTI-related E. coli. The evolutionary relationship of UcaA, PmpA and various other fimbrial subunit proteins is presented in a phylogenetic tree.
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The gene for Campylobacter trigger factor: evidence for multiple transcription start sites and protein products
More LessA gene encoding a protein of apparent molecular mass 56 kDa that shares 31 % identity with the amino acid sequence of trigger factor from Escherichia coli (a protein thought to be involved in cell division), was cloned from Campylobacter jejuni NCTC 11168. The clone was selected from a lambda ZAP II genomic DNA library following an immuno-screen using antiserum raised against glycine-extractable proteins from C. jejuni. The gene has two potential initiation codons, giving rise to two possible nested protein products. Complex differential growth-phase-dependent transcripts give rise to these products.
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Molecular characterization of katA from Campylobacter jejuni and generation of a catalase-deficient mutant of Campylobacter coli by interspecific allelic exchange
More LessA gene encoding catalase (hydrogen-peroxide: hydrogen-peroxide oxidoreductase; EC 1.11.1.6) from Campylobacter jejuni was cloned by functional complementation of a catalase-deficient mutant of Escherichia coli. The catalase structural gene, designated katA, was assigned by subcloning and its nucleotide sequence determined. The deduced protein product of 508 amino acids, which had a calculated molecular mass of 58346 Da, was found to be structurally and enzymically similar to hydrogen-peroxidases from other bacterial species. The region of DNA containing the structural catalase gene was disrupted by insertion of a tetracycline-resistance marker and the modified sequence then introduced into a strain of Campylobacter coli via natural transformation. Genetic and enzymic analyses of a tetracycline-resistant C. coli transformant confirmed that catalase-deficient mutants had arisen via interspecific allelic exchange. Compared to the isogenic parental strain the mutant was more sensitive to killing by H2O2.
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Subcellular location of XpsD, a protein required for extracellular protein secretion by Xanthomonas campestris pv. campestris
More LessThe last ORF of an xps gene cluster, designated xpsD, is required for the secretion of extracellular enzymes across the outer membrane in Xanthomonas campestris pv. campestris. It could encode a protein of 759 amino acid residues. A consensus N-terminal lipoprotein signal peptide was revealed from its deduced amino acid sequence. A [3H]palmitate labelling experiment indicated that XpsD was fatty-acylated. Differential extraction with Triton X-100 disclosed that XpsD was fractionated with the outer membrane. Sucrose gradient sedimentation analysis of total membranes also indicated that XpsD was mainly located in the outer membrane. At least part of XpsD is exposed to the cell surface as suggested by trypsin experiment results. Intact cells pretreated with antibody against XpsD could indirectly be labelled with fluorescent agent. When the N-terminal lipoprotein signal peptide was replaced with a nonlipoprotein signal peptide cleavable by signal peptidase I, non-fatty-acylated XpsD was synthesized. Its subcellular location was indistinguishable from that of the fatty-acylated XpsD. Complementation of an xpsD::Tn5 mutant of X. campestris pv. campestris indicated that this non-fatty-acylated XpsD remains functional in extracellular protein secretion. A stable, C-terminal truncated protein, XpsDd414-759, was synthesized from a mutated xpsD gene. Although it stayed associated with the outer membrane and exposed to the cell surface, it no longer could complement the xpsD::Tn5 mutant of X. campestris pv. campestris.
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Two genes encoding proteins with similarities to rubredoxin and rubredoxin reductase are required for conversion of dodecane to lauric acid in Acinetobacter calcoaceticus ADP1
More LessMutants of Acinetobacter calcoaceticus ADP1 unable to grow on dodecane, but retaining the ability to grow on lauric acid were isolated after ethylmethanesulphonate (EMS) treatment. This growth deficiency was complemented by a clone from a gene library constructed from chromosomal DNA of the wild-type strain. The complementing DNA mapped in a gene encoding a polypeptide with homology to rubredoxins. The deduced putative rubredoxin amino acid sequence is more similar to related proteins from Gram-positive bacteria than to the Pseudomonas oleovorans rubredoxin involved in alkane oxidation. An adjacent gene encodes a protein with similarity to rubredoxin reductase from Pseudomonas oleovorans and related NAD(P)-dependent reductases. Disruption of the rubredoxin-encoding gene by insertion of a KmR/lacZ cassette rendered the resulting strain unable to grow on dodecane or hexadecane. This demonstrates that these genes are necessary for alkane degradation. Transcriptional fusion of lacZ to the rubredoxin-encoding gene led to low level constitutive -galactosidase expression, whereas the fusion oriented in the opposite direction was not expressed.
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A Bacillus subtilis spore coat polypeptide gene, cotS
More LessA gene, cotS, encoding a spore coat polypeptide of Bacillus subtilis, was isolated from an EcoRI fragment (54 kb) of the chromosome by using synthetic oligonucleotide probes corresponding to the NH2-terminal amino acid sequence of Cot40-2 previously purified from the spore coat of B. subtilis. The nucleotide sequence (2603 bp) was determined and sequence analysis suggested the presence of two contiguous ORFs, ORF X and cotS, followed by the 5'-region of an additional ORF, ORF Y, downstream of cotS. The cotS gene is 1053 nucleotides long and encodes a polypeptide of 351 amino acids with a predicted molecular mass of 41083 Da. The predicted amino acid sequence was in complete agreement with the NH2-terminal amino acid sequence of Cot40-2. The orfX gene is 1131 nucleotides long and encodes a polypeptide of 377 amino acids with a predicted molecular mass of 42911 Da. The gene product of cotS was confirmed to be identical to Cot40-2 by SDS-PAGE and immunoblotting from Escherichia coli transformed with a plasmid containing the cotS region. Northern hybridization analysis indicated that a transcript of cotS and orfX appeared at about 5 h after the onset of sporulation. The transcriptional start point determined by primer extension analysis suggested that -10 and -35 regions are present upstream of orfX and are very similar to the consensus sequence for the k-dependent promoter. Terminator-like sequences were not found in the DNA fragment (2603 bp) sequenced in this paper, which suggested that the cotS locus may be part of a multicistronic operon. The cotS gene is located between dnaB and degQ at about 270-275 on the genetic map. Insertional mutagenesis of the cotS gene by introducing an integrative plasmid resulted in no alteration of growth or sporulation, and had no effect on germination or resistance to chloroform.
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Discovery of a ptsHl operon, which includes a third gene (ptsT), in the thermophile Bacillus stearothermophilus
More LessThe discovery of a ptsHl operon in Bacillus stearothermophilus XL-65-6 coupled with our previous report of a cel operon (Lai Ingram, J Bacteriol 175, 6441-6450, 1993) demonstrates that this thermophilic organism contains all of the genes required for cellobiose uptake by the phosphoenolpyruvate-dependent phosphotransferase system (PTS). Genes encoding the two general PTS proteins, HPr (ptsH) and enzyme l (ptsl), were cloned and sequenced. These form an operon which includes a third small gene (ptsT) of unknown function (encoded product M r 18428). Both ptsH and ptsl were expressed at high levels from a single plasmid in Escherichia coli and complemented corresponding host mutations. Although the translated sequences for these genes were similar to homologues from Gram-positive mesophiles (64-77% identity), the B. stearothermophilus gene products were unusual in having a higher predicted pi and fewer negatively charged amino acid residues. Enzyme I also contained more alanine and leucine than mesophilic counterparts. Interestingly, ptsT inhibited the growth of E. coli ptsl mutants at 37°C. No such inhibition was observed during incubation at a lower temperature (30°C) or in E. coli DH5α, which is wild-type for ptsl. The predicted translation product from ptsT contained a high proportion of basic amino acids (27%) and had a high predicted pl (pH 117), properties similar to bacterial histone-like proteins, but did not exhibit homology to any sequences in the current database. Regions upstream and downstream from the ptsHl operon contain genes with homology to Bacillus subtilis ptsG and wapA (wall-associated protein), respectively.
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- Pathogenicity And Medical Microbiology
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Four glucosyltransferases, GtfJ, GtfK, GtfL and GtfM, from Streptococcus salivarius ATCC 25975
More LessThe four recombinant glucosyltransferases (GTFs), GtfJ, GtfK, GtfL and GtfM, that had previously been cloned from Streptococcus salivarius ATCC 25975, were individually expressed in Escherichia coli and their glucan products and kinetic properties were analysed. GtfJ was a primer-dependent GTF which synthesized an insoluble glucan composed mainly of α-(13)-linked glucosyl residues in the presence of dextran T-10. GtfK was primer-stimulated, and produced a linear soluble dextran without any detectable branch points both in the absence and in the presence of dextran T-10. GtfL was primer-independent and produced a mixed-linkage insoluble glucan composed of approximately equal proportions of α-(13)-and α-(16)-linked glucosyl residues. GtfL was inhibited by dextran T-10. GtfM was primer-independent and produced a soluble dextran with approximately 5% α-(13)-linked glucosyl residues. GtfM was essentially unaffected by the presence of dextran T-10. The results confirmed that each enzyme represented one of the four possible combinations of primer-dependency and product solubility and that each possessed unique biosynthetic properties. The soluble dextrans formed by GtfK and GtfM, as well as the mixed-linkage insoluble glucan formed by GtfL, were also capable of acting as primers for the primer-dependent GtfJ and the primer-stimulated GtfK. Unexpectedly, the linear dextran produced by GtfK was by far the least effective either at priming itself or at activating and priming the primer-dependent GtfJ.
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- Physiology And Growth
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Actin cortical cytoskeleton and cell wall synthesis in regenerating protoplasts of the Saccharomyces cerevisiae actin mutant DBY 1693
More LessThe relationship between the actin cytoskeleton and cell wall synthesis was studied by light and electron microscopy in protoplasts of Saccharomyces cerevisiae DBY 1693 containing the act1-1 allele. Since protoplasting also disturbs the actin cytoskeleton, these mutant protoplasts had a double error in their actin cytoskeletons. In the period between the onset of wall synthesis and completion of the wall, protoplasts grown at the permissive temperature showed an even distribution of actin patches all over the surface on which a new cell wall was being synthesized. After wall completion, actin patches partially disappeared, but then re-appeared, accumulated in growth regions at the start of polarized growth. This was compared with the pattern of actin patches observed in intact temperature-sensitive actin mutant cells cultivated at the permissive temperature. Electron microscopy of freeze-etched replicas revealed finger-like invaginations of the plasma membrane in both the actin mutant cells and their protoplasts. These structures showed a very similar distribution to the actin patches detected by rhodamine phalloidin staining in the fluorescence microscope. A hypothesis is presented, explaining the role of actin patches/finger-like invaginations of the plasma membrane in the synthesis of β-(13)-D-glucan wall microfibrils in yeast cells.
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Choline- and acetylcholine-induced changes in the morphology of Fusarium graminearum: evidence for the involvement of the choline transport system and acetylcholinesterase
More LessThe response of Fusarium graminearum to choline, acetylcholine and a number of related analogues was investigated and their ability to induce a morphological response quantified. A number of mutants resistant to the alkylating agent nitrogen mustard (nim strains) were generated and found to have lost the ability to transport choline. These mutants were found to be insensitive to choline and acetylcholine but not to betaine, ethanolamine and other analogues. In addition, the non-competitive inhibitor hemicholinium-3 was also found to reduce the morphological effect of choline, proving that transport of choline into the hypha is essential for the morphological response. Acetylcholinesterase inhibitors blocked the morphological response to acetylcholine but had no effect on the response to choline, suggesting the presence of a membrane- or wall-bound acetylcholinesterase that hydrolyses acetylcholine to choline which subsequently induces the morphological response. Studies on the in vivo chitin synthase activity revealed that addition of choline caused a transient 75% increase in chitin synthase activity within 30 s, the rate rapidly returning to that observed before the addition of choline. No such effect was observed with the nim mutants.
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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)