Isolation and Properties of Spore Germination Mutants of Bacillus subtilis 168 Deficient in the Initiation of Germination

Abstract

Two spore germination mutants of Bacillus subtilis 168 (GerA38 and GerA44) deficient at a very early stage of germination prior to loss of heat resistance and absorbance were isolated. In contrast to the wild-type their spores required higher concentrations of germinant and had a slower germination rate and longer average microlag in l-alanine, l-α-aminobutyrate, dl-β-aminobutyrate and l-valine. Although wild-type spores germinated in 0·1 m-CyCloleucine the mutants did not, but did so normally in l-asparagine plus glucose, fructose and KCl. GerA44 was more defective than GerA38. Their germination abnormalities were partially corrected if glucose, fructose and KCl were added to l-alanine or l-valine. Germination of both mutants in l-alanine was more sensitive than the wild-type to inhibition by d-alanine, the sensitivity of GerA44 being greater than that of GerA38. Two other GerA mutants which did not germinate in L-alanine, even at high concentrations, were able to use it as a source of carbon or nitrogen at rates equal to those of the wild-type. A similar mutant and GerA44 show normal chemotaxis to l-alanine. Thus, the deficiencies of GerA mutants appear to be spore specific. GerA38 and gerA44 mutations were approximately 75% and 43% cotransduced with cysB and thr-5, respectively, with phage PBS1. They mapped within a cluster of gerA mutations that were 70–90% cotransduced with citG4 by phage SPP1. Although other GerA mutants cannot germinate in l-alanine plus KCl no difference in map location between their mutations and gerA38 and gerA44 could be detected.