Regulation of Cell Division in a Temperature-Sensitive Division Mutant of Escherichia coli
AUTOR(ES)
Stone, A. B.
RESUMO
Escherichia coli fil ts forms multinucleate filaments when suspensions of about 107 organisms per ml are shifted from 37 to 43 C in rich medium. Occasional septation continues, chiefly at the poles, and immediately becomes more frequent when the filaments are returned to 37 C. The addition of chloramphenicol (200 μg/ml) at either temperature initially stimulates the formation of polar septa. When very dilute suspensions of the strain (<106 organisms per ml) are shifted to the restrictive temperature, the inhibition of septation is more complete and only seldom reversible. Conversely, cell division is little affected when suspensions of >108 organisms per ml, or microcolonies of several hundred organisms on agar, are incubated at 43 C; evidence is presented that this is a consequence of a slight reduction in the mutant's growth rate. In certain media, septation is blocked irreversibly by even brief exposure to 43 C, after which cell elongation without division proceeds at 37 C for some hours. Several findings, when considered together, suggest that the cytoplasmic membrane is normal at the restrictive temperature, and that the block in septation is caused by a defect in the cell wall: it is largely overcome by NaCl, but not by sucrose; in some circumstances the filaments become swollen and develop localized bulges in the wall, yet the membrane remains intact and retains its selective permeability; lastly, the strain is insensitive to deoxycholate at both temperatures. The mutation has been mapped between arg B and thr, at a locus which appears to be distinct from others known primarily to influence cell division.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=285440Documentos Relacionados
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