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Research has been conducted on the DtxR-dependent iron-regulated promoter from Corynebacterium diphtheriae. The cloning and characterization of this promoter have been carried out via the use of the systematic evolution of ligands by exponential enrichment-like selection method and the details are reported.

A study was conducted to examine the expressions of glnB and a glnB-like gene in a mutant of the nonsulfur purple photosynthetic bacterium Rhodobacter spaeroides. Gamma-glutamyltransferase assay was carried out at pH 7.5 to determine glutamine synthetase levels. Results indicated that glnK expression was derepressed during the presence of ammonia in photoheterotrophic conditions. Findings also showed that carbon metabolism supports a critical function in regulating nitrogen metabolism.

The role of the regB gene in bacterial signal transduction and CO2 fixation regulation in Rhodobacter sphaeroides was studied. Results revealed that aside from photosystem synthesis, the gene also plays a crucial role in the control of the Calvin cycle CO2 fixation operon. When light is available, regulation proceeds anaerobically. In the dark, however, it occurs aerobically. This suggests that regB belongs to a two-component system which codes for a sensor kinase controlling the regulation of light-independent and dependent CO2 fixation and the biosynthesis of the photosystem.

Research describes cloning and gene expression of Klebsiella oxytoca xylodextrin utilization operon, encoding a xylobiose/cation symport, and a new xylosidase in Escherichia coli. The functional expression of the genes in E. coli KO11 demonstrates the metabolism of soluble beta-1,4-linked xylodextrins, which display up to six xylosyl residues.

Abstract: Bacteria in the genus Bifidobacterium are commonly known as beneficial colonizers in the human gastrointestinal tract. We found that, when these anaerobic organisms were grown in culture media without the reducing agent, cysteine, they produced intensely stained intracellular granules reminiscent of polyphosphate granules (poly P) produced by other bacteria in response to certain environmental signals, such as starvation and oxidative stress. The addition of cysteine led to a significant reduction in granule formation in bifidobacteria. Specific microscopic staining showed that the intracellular granules in Bifidobacterium scardovii were consistent with the poly P granules. In addition, the expression of the putative polyphosphate kinase gene responsible for poly P synthesis showed a 16-fold increase in the granule-forming cultures of B. scardovii compared with the nongranule-forming cultures, suggesting a role of poly P production in the oxidative stress response. Furthermore, the granule-forming cells exhibited a higher acid tolerance and a higher degree of cell surface hydrophobicity than the nongranule-forming cells. Therefore, we propose that Bifidobacterium cells produce poly P as a part of the oxidative stress response, which in turn allows the cells to better tolerate other environmental stresses such as acidic pH and perhaps allows better host colonization in vivo. [Copyright &y& Elsevier]