Author/Editor		Kuhar, Irena; Žgur-Bertok, Darja
Title		Transcription regulation of the colicin K cka gene reveals induction of colicin synthesis by differential responses to environmental signals
Type		članek
Source		J Bacteriol
Vol. and No.		Letnik 181, št. 23
Publication year		1999
Volume		str. 7373-80
Language		eng
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-IacZ 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 22oC. 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.
Descriptors		COLICINS ESCHERICHIA COLI GENES, STRUCTURAL, BACTERIAL GENE EXPRESSION REGULATION, BACTERIAL PLASMIDS CULTURE MEDIA, CONDITIONED TEMPERATURE HYDROGEN-ION CONCENTRATION CLONING, MOLECULAR POLYMERASE CHAIN REACTION CYCLIC AMP FATTY ACIDS, VOLATILE MITOMYCIN C BASE SEQUENCE BETA-GALACTOSIDASE