Characterization and mapping of Bacillus subtilis gerD mutants.

Abstract

A mutantof Bacillus subtilis 168 unable to germinate in DLalanine + fructose + glucose was isolated and proved to be deficient in response to fructose. Spores of this mutant responded to L-alanine fairly well although the germination rate was slower than the wild type. Analysis of the effect of fructose on the D-alanine inhibition of L-alanine-triggered germination showed that in wild type spores, fructose reversed the inhibition by lowering the spore's affinity with D-alanine whereas the mutant spores lacked this response. Since the mutation was mapped in the gerD locus, a standard gerD strain, 4738 (gerD48), was studied for comparison.Strain 4738 showed similar germination properties except that germination of this strain in L-alanine was much slower. These findings revealed a germinant-specific character of gerD mutants whose defect had been regarded as non-specific with respect to germinants. PBS! transduction crosses suggested the gene order cysA-attSPO2-gerD-ada.

Role of GerD in Germination of Bacillus subtilis Spores

“…As noted above, previous work indicates that gerD mutant spores are slow to germinate with both L-alanine and AGFK, although this is reported to be to different extents (14,18,35). The gerD mutant spores do germinate in L-alanine, albeit slower than wild-type spores; however, the decrease in the rate of gerD mutant spore germination compared to that of wildtype spores is much greater in AGFK (14,18,35).…”

“…The gerD mutant spores do germinate in L-alanine, albeit slower than wild-type spores; however, the decrease in the rate of gerD mutant spore germination compared to that of wildtype spores is much greater in AGFK (14,18,35). This finding, as well as the much-improved germination with L-alanine of gerD mutant spores prepared in a resuspension medium (RM), a defined minimal medium (21,32), has led to the suggestion that GerD may not be an essential component of the spore germination apparatus (35).…”

“…Spores of gerA mutants are defective in germination with L-alanine, and spores of gerB or gerK mutants are defective in germination with AGFK. In addition, gerD and gerF mutants whose spores are affected in their germination with both L-alanine and AGFK have been identified (14,18,19,20). Spores of gerD and gerF mutants have a defect early in germination, before the release of the spore's large depot of pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]).…”

Analysis of transcriptional control of the gerD spore germination gene of Bacillus subtilis 168

“…The gerD locus consists of a single gene encoding a predicted polypeptide of 21,117 Da, which is largely hydrophilic but contains a hydrophobic region at the N terminus resembling a signal peptide (26). The GerD protein is an important component of the normal germination of B. subtilis spores; the spore's response to the amino acid and sugar (AGFK) combination is abolished in a gerD mutant, and the response to L-alanine is dramatically slower (12,19). It has been postulated that gerD mutants are defective in the binding of fructose (12) to the spore prior to the initiation of germination.…”

Nucleotide sequence and gene organization of the gerK spore germination locus of Bacillus subtilis 168.

“…If we assume that gerK and gerB products form a functional receptor complex only when they are mixed together, it may be explainable that ALA can induce germination in its own right whereas GLC and ASN can not. The role of fructose is rather complex, fructose is suggested to act by binding with the gerD product which is a relatively small (185 aa) protein with a signal-like sequence at the N-terminus (8,22).…”