- Volume 139, Issue 2, 1993
Volume 139, Issue 2, 1993
- Genetics And Molecular Biology
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DNA sequence of themurE-murD region of Bacillus subtilis 168
More LessThe sequence of a 4·4 kbp region of DNA from Bacillus subtilis 168, lying between sporulation genes spoVD and spoVE , has been determined as part of the B. subtilis genomic sequencing programme. The region contains three genes with high sequence similarity to the murE , mraY and murD genes of Escherichia coli . The products of these genes are likely to catalyse various steps in the formation of the precursors for peptidoglycan synthesis in B. subtilis . The regions at 133° on the standard genetic map of the B. subtilis chromosome, and in the 2 min region of the E. coli genetic map, are now shown to contain a large cluster of functionally related genes. Although the linear order of the genes in the cluster is conserved, three genes that are present in the E. coli chromosome, and which are likely to be essential for peptidoglycan synthesis in both organisms, are absent from this region of the B. subtilis chromosome. In general, the B. subtilis cluster differs from that of E. coli in having more extensive intergenic regions, with less potential for translational coupling.
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- Physiology And Growth
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Maltoporins and maltose-binding proteins of Yersinia enterocolitica
More LessTwo components of the Yersinia enterocolitica maltose transport system, maltoporin (OmpM) and an osmotically shockable periplasmic maltose-binding protein (MBP) were identified. The synthesis of OmpM (apparent M r 43000) and transport of maltose into cells of Y. enterocolitica were induced by maltose and maltodextrins. A mutant lacking OmpM was drastically impaired in maltose transport, independent of induction by maltose. The MBP of Y. enterocolitica (apparent M r 40000) was found in the osmotic shock fluid. Its synthesis was induced by maltose. Moreover, rabbit antibodies raised against the MBP of E. coli cross-reacted with the analogous protein from Y. enterocolitica. The MBP of Y. enterocolitica restored the maltose transport activities in ΔmalE mutant cells of E. coli.
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Sulphonate utilization by enteric bacteria
More LessA variety of sulphonates were tested for their ability to serve as nutrients for Escherichia coli, Enterobacter aerogenes and Serratia marcescens. Cysteate, taurine and isethionate could not serve as sole sources of carbon and energy but, under aerobic conditions, could be utilized as sources of sulphur. Both sulphate and sulphonate supported equivalent cell yields, but the generation times varied with the sulphonate being metabolized. The sulphonate-S of HEPES buffer, dodecane sulphonate and methane sulphonate was also utilized by some strains, whereas the sulphonate-S of taurocholate was not. None of the sulphonates tested served as a sulphur source for growth under anaerobic conditions. Sulphonate utilization appears to be a constitutive trait; surprisingly, however, cells of E. coli and Ent. aerogenes utilized sulphate-S in preference to that of sulphonate, when both were present. E. coli mutants unable to use sulphate as a source of sulphur because of deficiencies in sulphate permease, ATP sulphurylase, adenylylsulphate kinase (APS kinase) or glutaredoxin and thioredoxin were able to utilize sulphonates; hence sulphate is not an obligatory intermediate in sulphonate utilization. However, mutants deficient in sulphite reductase were unable to utilize sulphonates; therefore, this enzyme must be involved in sulphonate utilization, though it is not yet known whether it acts upon the sulphonates themselves or upon the inorganic sulphite derived from them.
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The carbon starvation stimulon in the marine Vibrio sp. S14 (CCUG 15956) includes three periplasmic space protein responders
More LessGrowth arrest and long-term starvation in the marine Vibrio sp. S14 induce alterations of the cell envelope as well as a sequential expression of starvation-specific polypeptides. The induction and accumulation of three dominant carbon-starvation-induced periplasmic space protein responders of molecular mass 120 (Cspl), 37 (Csp5) and 30 kDa (Csp6), were examined under different starvation and stress conditions. All three proteins were increasingly synthesized in response to carbon and multiple-nutrient starvation, but not during nitrogen and phosphorus starvation, nor in response to the imposition of stress conditions. Csp1 exhibited a more than 100-fold increased relative induction by carbon and multiple-nutrient starvation and was continuously synthesized throughout the experiment. Induction of Csp1 was completely repressed by all conditions other than carbon starvation. A less than fivefold increase in induction was monitored for the transient responders Csp5 and Csp6 within the first few hours of carbon starvation. Interestingly, Csp6 exhibited an increased transient induction at the onset as well as after 24 h of starvation. Accumulation of the three proteins was monitored by Western blot analysis using specific antisera. Of the conditions tested, long-term accumulation of these proteins was only detected when Vibrio sp. S14 cells were exposed to carbon and multiple-nutrient starvation. These results are discussed in relation to the recent finding that formation of starvation- and stress-resistant marine Vibrio is induced by carbon but not nitrogen or phosphorus starvation, and that Csp1, Csp5 and Csp6 will allow detailed studies of the carbon starvation stimulon.
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Glycogen in Phycomyces blakesleeanus: influence of growth conditions and nutrient limitation
More LessThe accumulation and mobilization of glycogen have been measured in Phycomyces blakesleeanus subjected to a variety of environmental and nutritional conditions. Depending on the conditions and the stage in the life cycle, glycogen represented from 10% to less than 1% of the dry weight of the mycelia. Maximum values were observed during the exponential growth phase irrespective of the carbon source used. The highest glycogen levels were detected with 2% (w/v) sorbitol as carbon source. A low glycogen content was present during growth on acetate. In these cultures glycogen was presumably synthesized from glyoxylate-dependent metabolites. Glycogen accumulated in cultures deprived specifically of nitrogen or phosphorus in the presence of an excess of a usable carbon source, suggesting that reserve carbohydrate accumulation is a general response to nutrient limitation. However, temporary starvation caused by removal of glucose or by transfer to media with relatively poor carbon sources such as acetate led to mobilization of glycogen in the mycelia. During sporulation the disappearance of glycogen was almost complete.
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