Heat-sensitive Lysis Mutants of Bacillus subtilis 168 Blocked at Three Different Stages of Peptidoglycan Synthesis

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Abstract
Summary: Three heat-sensitive mutants of Bacillus subtilis 168, which lysed at the non-permissive temperature, have been shown under these conditions to be defective in the synthesis of peptidoglycan. This was caused by lesions in three different stages of peptidoglycan synthesis. In one mutant (ddl), D-alanine: D-alanine ligase was defective, leading to the accumulation of UDP-MurAc-L-Ala-D-Glu-meso-A2pm; the ddl mutation was closely linked (87% cotransducible) with dal, specifying alanine racemase. In a second mutant (dapE), the lesion was in N-acetyl-L-diaminopimelate deacylase, resulting in UDP-MurAc-L-Ala-D-Glu being accumulated, whilst in a third mutant (ptg-1435), UDP-MurAc-L-Ala-D-Glu-meso-A2pm-D-Ala-D-Ala was the peptidoglycan precursor accumulated although the enzyme defect has not been ascertained. Both dapE and ptg-1435 were located between metC and pyr(AD), dapE being 25% cotransducible with pyr(AD), whilst ptg-1435 was 60 to 70% cotransducible with pyr(AD).

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