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The physiological and ecological role for the luxS gene in Lactobacillus reuteri 100-23C is defined by constructing a luxS mutant by insertional mutagenesis. The results show that LuxS influences important ecological attributes of L. reuteri 100-23C, the consequences of which are niche specific.

Four extracellular enzymes of the thermophilic bacterium Clostridium stercorarium are involved in the depolymerization of de-esterified arabinoxylan: Xyn 11A, Xyn10C, Bxl3B, and Arf51 B. They were identified in a collection of eight clones producing enzymes hydrolysing xylan (xynA, xynB, xynC), [beta]-xyloside (bxlA, bxlB, bglZ) and [alpha]-arabinofuranoside (arfA, arfB). The modular enzymes Xyn11A and Xyn10C represent the major xylanases in the culture supernatant of C. stercorarium. Both hydrolyse arabinoxylan in an endo-type mode, but differ in the pattern of the oligosaccharides produced. Of the glycosidases, Bxl3B degrades xylobiose and xylooligosaccharides to xylose, and Arf51B is able to release arabinose residues from de-esterified arabinoxylan and from the oligosaccharides generated. The other glycosidases either did not attack or only marginally attacked these oligosaccharides. Significantly more xylanase and xylosidase activity was produced during growth on xylose and xylan. This is believed to be the first time that, in a single thermophilic micro-organism, the complete set of enzymes (as well as the respective genes) to completely hydrolyse de-esterified arabinoxylan to its monomeric sugar constituents, xylose and arabinose, has been identified and the enzymes produced in vivo. The active enzyme system was reconstituted in vitro from recombinant enzymes.

Research investigates the bacterial population changes at the species level during sourdough fermentation, under different ecological conditions, using two lactic acid bacteria-specific polymerase chain reaction-denaturing gradient gel electrophoresis method. Results agree with those from culturing and only a few Lactobacillus species become competitive and dominant.

Researchers describe the development of PCR primers specific for Lactobacillus, Pediococcus, Leuconostoc, and Weissella. Lactic acid bacteria make up less than 1% of the intestinal microflora, and are not easily detectable using universal PCR primers.

Research was conducted to examine the oxygen-dependent regulation of the expression of the catalase gene katA of Lactobacillus sakei LTH677 as well as in the recombinant strains of L curvatus, L casei and Escherichia coli. Results demonstrate unique combinations of properties. The catalase activity responded to exposure of the cells to oxygen. Regulation occurred at the transcriptional level and a unique sequence involved in regulation of the promoter was identified.

Strains of Lactobacillus acidophilus, L. gasseri and L. johnsonii were differentiated by SDS-PAGE protein analysis, 23S rRNA-targeted oligonucleotide hybridization and 16S rRNA sequence comparisons. Protein electrophoretic profiles clustered the strains into two well-defined clusters, with L. acidophilus in one cluster and L. gasseri and L. johnsonii in the second. DNA hybridization analysis differentiated between all the three species, and the 23S-rRNA-targeted oligonucleotide probes could be used to classify strains into their particular species. 16S rRNA sequence comparisons showed that L. johnsonii is closely related to L. gasseri.