title: Induction of beta-lactamase influences the course of development in Myxococcus xanthus.
abstract: Myxococcus xanthus is a gram-negative bacterium that develops in response to starvation on a solid surface. The cells assemble into multicellular aggregates in which they differentiate from rod-shaped cells into spherical, environmentally resistant spores. Previously, we have shown that the induction of beta-lactamase is associated with starvation-independent sporulation in liquid culture (K. A. O'Connor and D. R. Zusman, Mol. Microbiol. 24:839-850, 1997). In this paper, we show that the chromosomally encoded beta-lactamase of M. xanthus is autogenously induced during development. The specific activity of the enzyme begins to increase during aggregation, before spores are detectable. The addition of inducers of beta-lactamase in M. xanthus, such as ampicillin, D-cycloserine, and phosphomycin, accelerates the onset of aggregation and sporulation in developing populations of cells. In addition, the exogenous induction of beta-lactamase allows M. xanthus to fruit on media containing concentrations of nutrients that are normally too high to support development. We propose that the induction of beta-lactamase is an integral step in the development of M. xanthus and that this induction is likely to play a role in aggregation and in the restructuring of peptidoglycan which occurs during the differentiation of spores. In support of this hypothesis, we show that exogenous induction of beta-lactamase can rescue aggregation and sporulation of certain mutants. Fruiting body spores from a rescued mutant are indistinguishable from wild-type fruiting body spores when examined by transmission electron microscopy. These results show that the signal transduction pathway leading to the induction of beta-lactamase plays an important role in aggregation and sporulation in M. xanthus.
authors.affiliation: Department of Molecular Biology, University of California, Berkeley, California 94720-3204, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: O'Connor
authors.forename: D R
authors.initials: DR
authors.lastname: Zusman
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002364:Caseins; D002633:Chemotaxis / Q000235:genetics; D003470:Culture Media; D003523:Cycloserine / Q000494:pharmacology; D004790:Enzyme Induction; D005578:Fosfomycin / Q000494:pharmacology; D009154:Mutation; D016941:Myxococcus xanthus / Q000187:drug effects / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D011492:Protein Hydrolysates; D015398:Signal Transduction; D013171:Spores, Bacterial / Q000187:drug effects / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D014640:Vancomycin / Q000494:pharmacology; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D002364:Caseins; C063576:CsgA protein, Myxococcus xanthus; D003470:Culture Media; D011492:Protein Hydrolysates; C026375:trypticase-soy broth; D005578:Fosfomycin; D014640:Vancomycin; D000667:Ampicillin; D003523:Cycloserine; D001618:beta-Lactamases