~~ ~Wall turnover in Myxococcus xanthus has been studied by measuring the incorporation and release of meso-diamino[14C]pimelic acid. The rate of turnover was low in vegetatively growing organisms. Following the addition of 0.5 M-glycerol to induce myxospore formation in organisms that had been labelled for one generation in the absence of glycerol, increased rates of incorporation and release were observed both before and during cellular morphogenesis. Chloramphenicol inhibited glycerol-induced myxospore formation, but only partially blocked the release of rneso-diaminopimelic acid. A mutant, non-inducible by glycerol, was isolated and was found to show no increased autolytic activity in the presence of glycerol. Both parent and mutant strains could be induced to form myxospores by 17 mMphenethyl alcohol, but with both strains there was only a slight increase in meso-diaminopimelic acid release following induction.

The effect of dif€erent p-lactam antibiotics on the growth and morphology of Myxococcus xanthus has been examined. Exposure to penicillin and cephalexin resulted in spheroplast and filament formation, respectively. Mecillinam appeared to inhibit cell elongation and caused the formation of bent cells with central bulges. Myxospore formation was inhibited by cephalexin but not by mecillinam, although myxospores formed in the presence of mecillinam showed defects after germination. Germination of myxospores involves substantial cell-wall turnover as measured by uptake and loss of meso-diami~io[~~Clpimelic acid. Although turnover was observed when myxospores were germinated in the presence of mecillinam, the bacteria remained as spheres. Growth of these 'germinated myxospores' following removal of mecillinam indicated that wall material laid down during the early stages of germination is stable and a rod shape could be re-established only by bipolar growth of new wall.

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