A protocol designed to isolate mutants with thermosensitive (Ts) synthesis of the bacteriophage φ29 receptor, which includes the major wall teichoic acid in Bacillus subtilis 168, yielded a significant enrichment for Ts growth mutants among colonies surviving φ29 treatment. Nine mutants, Ts for both φ29 susceptibility and cell growth, harboured mutations which were located in the tag locus by PBS1 transduction and recombination index with the tag-1 marker. Physical mapping revealed that they were distributed on a segment of more than 4 kb. Chemical analysis of cell walls showed a marked reduction in phosphate relative to diaminopimelic acid content of all mutants at the non-permissive temperature. Differences between mutants were correlated with the distribution of tag mutations on the genetic map. We conclude (i) that the newly identified markers affect several genes involved in poly(glycerol phosphate) synthesis, and (ii) that on phosphate-rich media, cell growth cannot occur without the synthesis of the latter polymer.
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