- Volume 143, Issue 9, 1997
Volume 143, Issue 9, 1997
- Physiology And Growth
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The absence of D-alanine from lipoteichoic acid and wall teichoic acid alters surface charge, enhances autolysis and increases susceptibility to methicillin in Bacillus subtilis
More LessSummary: In Bacillus subtilis the physiological consequences of depriving lipoteichoic acid and wall teichoic acid of D-alanine ester were analysed using insertional inactivation of the genes of the dlt operon. Mutant strains which lacked positively charged D-alanine ester in teichoic acids bound more positively charged cytochrome C than other strains. These mutant strains also showed enhanced autolysis and a higher susceptibility to methicillin, which was expressed as accelerated wall lysis, a faster loss of viability and a slower recovery in the postantibiotic phase. The effects of methicillin could be suppressed by simultaneous addition of magnesium ions at low concentrations. The degradation of whole bacteria by bone-marrow-derived macrophages was not influenced by the surface charge and alanylation of the teichoic acids had no protective effect.
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Isolation of Aspergillus niger creA mutants and effects of the mutations on expression of arabinases and L-arabinose catabolic enzymes
Summary: Aspergillus niger mutants relieved of carbon repression were isolated from an areA parental strain by selection of colonies that exhibited improved growth on a combination of 4-aminobutanoic acid (GABA) and D-glucose. In addition to derepression of the utilization of GABA as a nitrogen source in the presence of D-glucose, three of the four mutants also showed derepression of L-alanine and L-proline utilization. Transformation of the mutants with the A. niger creA gene, encoding the repressor protein CREA, re-established the areA phenotype on GABA/D-glucose, identifying the mutations as creA d. The creA gene mapped on chromosome IV by linkage analysis and contour-clamped homogeneous electric field hybridization. The creA mutants obtained were used to study the involvement of CREA in repression by D-glucose of arabinases and L-arabinose catabolism in A. niger. In wild-type A. niger, α-L-arabinofuranosidase A, α-L-arabinofuranosidase B, endo-arabinase, L-arabinose reductase and L-arabitol dehydrogenase were induced on L-arabinose, but addition of D-glucose prevented this induction. Repression was relieved to varying degrees in the creA mutants, showing that biosynthesis of arabinases and L-arabinose catabolic enzymes is under control of CREA.
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Mutant studies of phosphofructo-2-kinases do not reveal an essential role of fructose-2, 6-bisphosphate in the regulation of carbon fluxes in yeast cells
More LessSummary: The effect of the allosteric regulator fructose-2, 6-bisphosphate (F2, 6bP) on the regulation of carbohydrate metabolism was investigated in vivo with Saccharomyces cerevisiae mutants containing no, very high or unregulated 6-phosphofructo-2-kinase activity. Simultaneous overproduction of F2, 6bP and 6-phosphofructo-1-kinase activity did not increase the glycolytic flux to ethanol. Overexpression of fructose-1, 6-bisphosphatase during growth on glucose in a mutant strain devoid of F2, 6bP did not cause pronounced effects on the cells. Moreover, high levels of F2, 6bP during growth on ethanol in a strain with a highly active 6-phosphofructo-2-kinase enzyme did not affect either carbon flux to glycogen or growth rate. Site-directed mutagenesis of 6-phosphofructo-2-kinase (Pfk26) revealed that serine 644 is involved in the activation of Pfk26 by protein kinase A phosphorylation, but that, additionally, the enzyme can be further activated by phosphorylation of another amino acid residue. The results demonstrate that F2, 6bP is not needed to sustain an adequate glycolytic flux under fermentative conditions, but rather is concerned with the homeostasis of metabolite concentrations. Moreover, they fail to indicate a physiological significance for inhibition of fructose-1,6-bisphosphatase by F2,6bP.
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- Genome Analysis
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Sub-specific differentiation of intestinal spirochaete isolates by macrorestriction fragment profiling
More LessSummary: Macrorestriction fragment profile analysis by PFGE was used to distinguish intestinal spirochaetes, some of which were isolated from cases of swine dysentery and intestinal spirochaetosis in humans, pigs, mice, chickens and dogs. Macrorestriction fragment profiles using Smal and Sacll restriction enzymes were produced and used in statistical analysis. This permitted the division of the isolates into two major clusters. One cluster contained isolates which were identified as Serpulina pilosicoli and the second cluster contained isolates identified as Serpulina hyodysenteriae by immunoblotting with species-specific mAbs. Both species contained sub-specific groups, although these rarely correlated with the source of the isolates. We conclude that PFGE is capable of sub-specific differentiation of intestinal spirochaetes, but that the current species contain a large variety of genotypes among which cross-species transmission may be feasible.
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Sequence of the Bacillus subtilis genome region in the vicinity of the lev operon reveals two new extracytoplasmic function RNA polymerase sigma factors SigV and SigZ
Summary: Two regions with sizes 18 900 and 25400 bp, which join previously known contigs containing levRDEFG, aadK and bit genes near 235δ of the Bacillus subtilis chromosome, were sequenced. Among others, two genes, which encode proteins homologous to RNA polymerase σ-factors, were identified within this region. The gene products designated SigV and SigZ, show the highest homology with σ-factors encoded by the gene carQ of Myxococcus xanthus and sigX (formerly orfX20) of B. subtilis, correspondingly. All σ-factors which show statistically significant homology to SigV and SigZ, belong to the ECF (extracytoplasmic functions) subfamily. SigV and SigZ do not have N-terminal sequence which prevents such proteins from binding to DNA without RNA polymerase core enzyme.
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- Corrigendum
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