THE GERB REGION OF THE BACILLUS-SUBTILIS-168 CHROMOSOME ENCODES A HOMOLOG OF THE GERA SPORE GERMINATION OPERON

Spores of gerB spore germination mutants of Bacillus subtilis 168 are defective in response to the germinative mixture of L-asparagine, gluc ose. fructose and potassium ions (AGFK), but are normal in the L-alani ne (ALA) triggered germination response. A lambda clone of 15 kbp carr ying the gerB region has been identified. Sequencing of the gerB regio n of the clone revealed a cluster of three ORFs encoding putative prot eins of 53.3, 41.3 and 42.4 kDa (GerBA, GerBB and GerBC, respectively) . The first two of these proteins have substantial hydrophobic regions and the third is a possible lipoprotein. At least two, and probably a ll three products are required for normal germination in AGFK. The thr ee proteins form a set of homologues of the products of the gerA opero n, mutations in which cause a defect in the ALA germination pathway, b ut cause no defect in AGFK. The GerB proteins show 42%, 31% and 35% id entity at the amino-acid level to the corresponding GerA proteins, and the homologues occur in the same order in both operons.