Bacillus subtilis is capable of producing 2,3-butanediol from acetoin by fermentation, but to date, the gene encoding the enzyme responsible, acetoin reductase/2,3-butanediol dehydrogenase (AR/BDH), has remained unknown. A search of the B. subtilis genome database with the amino acid sequences of functional AR/BDHs from Saccharomyces cerevisiae and Bacillus cereus resulted in the identification of a highly similar protein encoded by the B. subtilis ydjL gene. A knockout strain carrying a ydjL :: cat insertion mutation was constructed, which (i) abolished 2,3-butanediol production in early stationary phase, (ii) produced no detectable AR or BDH activity in vitro, and (iii) accumulated the precursor acetoin in early stationary phase. The ydjL :: cat mutation also affected the kinetics of lactate but not acetate production during stationary-phase cultivation with glucose under oxygen limitation. A very small amount of 2,3-butanediol was detected in very-late-stationary-phase (96-hour) cultures of the ydjL :: cat mutant, suggesting the existence of a second gene encoding a minor AR activity. From the data, it is proposed that the major AR/BDH-encoding gene ydjL be renamed bdhA .

The role of DNA repair by nonhomologous-end joining (NHEJ) in spore resistance to UV, ionizing radiation, and ultrahigh vacuum was studied in wild-type and DNA repair mutants ( recA , splB , ykoU , ykoV , and ykoU ykoV mutants) of Bacillus subtilis . NHEJ-defective spores with mutations in ykoU , ykoV , and ykoU ykoV were significantly more sensitive to UV, ionizing radiation, and ultrahigh vacuum than wild-type spores, indicating that NHEJ provides an important pathway during spore germination for repair of DNA double-strand breaks.

Previously, spontaneous rifampin resistance mutations were isolated in cluster I of the rpoB gene, resulting in amino acid replacements (Q469R, H482R, H482Y, or S487L) in the Bacillus subtilis RNA polymerase β subunit (W. L. Nicholson and H. Maughan, J. Bacteriol. 184: 4936-4940, 2002). In this study, each amino acid change in the β subunit was observed to result in its own unique spectrum of effects on growth and various developmental events, including sporulation, germination, and competence for transformation. The results thus establish the important role played by the RNA polymerase β subunit, not only in the catalytic aspect of transcription, but also in the regulation of major developmental events in B. subtilis .

The ability of terrestrial microorganisms to grow in the near-surface environment of Mars is of importance to the search for life and protection of that planet from forward contamination by human and robotic exploration. Because most water on present-day Mars is frozen in the regolith, permafrosts are considered to be terrestrial analogs of the martian subsurface environment. Six bacterial isolates were obtained from a permafrost borehole in northeastern Siberia capable of growth under conditions of low temperature (0 °C), low pressure (7 mbar), and a CO₂-enriched anoxic atmosphere. By 16S ribosomal DNA analysis, all six permafrost isolates were identified as species of the genusCarnobacterium, most closely related toC. inhibens(five isolates) andC. viridans(one isolate). Quantitative growth assays demonstrated that the six permafrost isolates, as well as nine type species ofCarnobacterium(C. alterfunditum,C. divergens,C. funditum,C. gallinarum,C. inhibens,C. maltaromaticum,C. mobile,C. pleistocenium, andC. viridans) were all capable of growth under cold, low-pressure, anoxic conditions, thus extending the low-pressure extreme at which life can function.