Studies on the mechanism of the osmoresistance of spores of Bacillus subtilis.

Aims: To determine the reason that spores of Bacillus species, in particular Bacillus subtilis, are able to form colonies with high efficiency on media with very high salt concentrations.

Methods And Results: Spores of various Bacillus species have a significantly higher plating efficiency on media with high salt concentration (termed osmoresistance) than do log or stationary phase cells. This spore osmoresistance is higher on richer media.

Effects of overexpression of nutrient receptors on germination of spores of Bacillus subtilis.

The rates of germination of Bacillus subtilis spores with L-alanine were increased markedly, in particular at low L-alanine concentrations, by overexpression of the tricistronic gerA operon that encodes the spore's germinant receptor for L-alanine but not by overexpression of gerA operon homologs encoding receptors for other germinants. However, spores with elevated levels of the GerA proteins did not germinate more rapidly in a mixture of asparagine, glucose, fructose, and K(+) (AGFK), a germinant combination that requires the participation of at least the germinant receptors encoded by the tricistronic gerB and gerK operons. Overexpression of the gerB or gerK operon or both the gerB and gerK operons also did not stimulate spore germination in AGFK.

The products of the spoVA operon are involved in dipicolinic acid uptake into developing spores of Bacillus subtilis.

Bacillus subtilis cells with mutations in the spoVA operon do not complete sporulation. However, a spoVA strain with mutations that remove all three of the spore's functional nutrient germinant receptors (termed the ger3 mutations) or the cortex lytic enzyme SleB (but not CwlJ) did complete sporulation. ger3 spoVA and sleB spoVA spores lack dipicolinic acid (DPA) and have lower core wet densities and levels of wet heat resistance than wild-type or ger3 spores.

Effect of chromosome location of Bacillus subtilis forespore genes on their spo gene dependence and transcription by E sigma F: identification of features of good E sigma F-dependent promoters.

Translational lacZ fusions to forespore genes of Bacillus subtilis were not expressed in spoIIAC (sigma F) or spoIIIE mutants when the lacZ fusions were integrated at the loci of the same genes or at the SP beta locus. However, some of these genes, including gerA, gpr, spoIIIG (sigma G), and sspE, were expressed in spoIIIE mutants and spoIIIE spoIIIG double mutants (but not in spoIIAC mutants) when the lacZ fusions were integrated at the amyE locus. When tested, the beta-galactosidase made in these mutants was found only in the forespore, and the 5' ends of the mRNAs produced in these mutants were identical to those in a Spo+ background.

Effects of mutant small, acid-soluble spore proteins from Bacillus subtilis on DNA in vivo and in vitro.

alpha/beta-type small, acid-soluble spore proteins (SASP) of Bacillus subtilis bind to DNA and alter its conformation, topology, and photochemistry, and thereby spore resistance to UV light. Three mutations have been introduced into the B. subtilis sspC gene, which codes for the alpha/beta-type wild-type SASP, SspCwt.