title: Transcription regulation of the colicin K cka gene reveals induction of colicin synthesis by differential responses to environmental signals.
abstract: Colicin-producing strains occur frequently in natural populations of Escherichia coli, and colicinogenicity seems to provide a competitive advantage in the natural habitat. A cka-lacZ fusion was used to study the regulation of expression of the colicin K structural gene. Expression is growth phase dependent, with high activity in the late stationary phase. Nutrient depletion induces the expression of cka due to an increase in ppGpp. Temperature is a strong signal for cka expression, since only basal-level activity was detected at 22 degrees C. Mitomycin C induction demonstrates that cka expression is regulated to a lesser extent by the SOS response independently of ppGpp. Increased osmolarity induces a partial increase, while the global regulator integration host factor inhibits expression in the late stationary phase. Induction of cka was demonstrated to be independent of the cyclic AMP-Crp complex, carbon source, RpoS, Lrp, H-NS, pH, and short-chain fatty acids. In contrast to colicin E1, cka expression is independent of catabolite repression and is partially affected by anaerobiosis only upon SOS induction. These results indicate that while different colicins are expressed in response to some common signals such as nutrient depletion, the expression of individual colicins could be further influenced by specific environmental cues.
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, 1000 Ljubljana, Slovenia.
authors.forename: I
authors.initials: I
authors.lastname: Kuhar
authors.forename: D
authors.initials: D
authors.lastname: Zgur-Bertok
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins; D003087:Colicins / Q000096:biosynthesis* / Q000235:genetics*; D003470:Culture Media / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors; D007763:Lac Operon / Q000235:genetics; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009995:Osmosis; D011422:Propionates / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013014:SOS Response, Genetics; D012808:Sigma Factor / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003087:Colicins; D003470:Culture Media; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D034982:Integration Host Factors; D011422:Propionates; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D016685:Mitomycin; D000242:Cyclic AMP; C029658:propionic acid; D019342:Acetic Acid