BIOCHEMICAL-ANALYSIS OF GERMINATION MUTANTS TO CHARACTERIZE GERMINANTRECEPTORS OF BACILLUS-SUBTILIS 1604 SPORES

Spores of Bacillus subtilis 1604 can be induced to germinate by incuba tion in L-Ala (the ALA pathway) or in a combination of beta-D-glucose (Glc), beta-fructose (Fru), L-Asn and K+ (the GFAK pathway). Biochemic al analysis of the germination response of a gerA mutant deficient in the ALA pathway revealed that L-Ala can replace L-Asn in the GFAK path way (the GFAlaK pathway). In contrast to the ALA pathway of both the w ild-type and of a gerB mutant, the GFAlaK pathway was insensitive to D -Ala and showed the same overall inhibitor profile as the GFAK pathway of wild-type and gerA spores. It is deduced that a second L-Ala recep tor with different characteristics to that functioning in the ALA path way is present in wild-type spores. Analysis of the germination respon se of a gerB mutant showed that whilst the rate of ALA germination cou ld be stimulated by Glc as well as by Fru in the presence of Glc, the spores could not germinate in GFAK. In addition, Glc and Fru were unab le to reverse D-Ala inhibition Of L-Ala germination which they do in t he wild-type. Thus, in the gerB mutant, the L-Ala/L-Asn receptor in th e GFAK pathway is defective. It is concluded that the germination rece ptors in the ALA and GFAK pathways can functionally interact with each other to initiate B. subtilis spore germination. This conclusion is d iscussed in relation to proposed models of triggering of spore germina tion.