Analysis of Myxococcus xanthus cell types by two-dimensional polyacrylamide gel electrophoresis.
Myxococcus xanthus is a gram-negative, soil-dwelling bacterium that undergoes development in response to depletion of nutrients. Whereas most cells aggregate into multicellular mounds in which they differentiate into spores, 10 to 20% of the developing cells remain outside fruiting bodies as peripheral rods. We used two-dimensional polyacrylamide gel electrophoresis to analyze the global expression of polypeptides in cells taken from six stages in the life cycle: vegetatively growing cells, cells 15 h after the induction of development, peripheral rods, prespores (sonication-sensitive, aggregated cells), fruiting-body spores (sonication-resistant, aggregated cells) 96 h after the induction of development, and glycerol-induced spores 15 h after induction. Seven hundred sixty-one discrete sample spots (SSPs) were identified among the six gels. Comparisons among the samples revealed that each sample had some unique SSPs, ranging from 0.3% of the 15-h developing cell SSPs to 17.9% of 96-h peripheral rod SSPs. Sixty-eight SSPs were ubiquitously distributed, but the relative amounts of these SSPs varied among the samples. Statistical analyses of the distribution and relative quantities of the SSPs indicate that, within a confidence level of greater than 99.99%, peripheral rods are significantly different from vegetatively growing cells, 15-h developing cells, prespores, fruiting-body spores, and glycerol-induced spores. In fact, among the six samples studied, only 15-h developing cells and glycerol-induced spores were similar to each other within a confidence level of P greater than or equal to 0.05. These results are consistent with the description of peripheral rods as a distinct developmental cell type.
O'Connor
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Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Zusman
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D001426:Bacterial Proteins / Q000096:biosynthesis*; D015153:Blotting, Western; D015180:Electrophoresis, Gel, Two-Dimensional; D015870:Gene Expression; D009231:Myxococcales / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D013171:Spores, Bacterial / Q000378:metabolism*
D001426:Bacterial Proteins