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Scientific
Publications - Work Done by Microbiology Reader
Vasil'eva SV, Iskandarova KA and Makhova EV, [Interference of inducible repair processes in Escherichia coli], (Russ.), Genetika, 1989, vol. 25, (12), pp. 2138-2150 ABSTRACT Radiation and the majority of chemical mutagens produce lesions
in the DNA of cells which provoke the induction--as a reverse response--of some
inducible repair processes. One of them is the adaptive response--highly
specific in the repair of damages, induced by alkylating agents. This repair
pathway decreases the toxic and mutagenic effects of many alkylating agents and
can be induced in Escherichia coli cells exposed to sublethal concentrations of
the same agents. By contrast, the SOS repair pathway in E. coli is non-specific
and transient phenomenon which leads, among other things, to bacterial
mutagenesis. It is controlled by the regulatory RecA protein which in its
activated form promotes the cleavage of LexA repressor, allowing for the
increased transcription of about 17 repressed genes--SOS regulon. The latter is
not associated with the adaptive response. Nevertheless, there are experimental
data indicating that the adaptive response is able to reduce some functions of
the SOS repair activity--W-reactivation, W-mutagenesis and lambda phage
induction. A relatively new bacterial short-term assay for genotoxicity, the SOS
chromotest with E. coli PQ37 as an indicator organism, makes it possible to
measure SOS induction indirectly, on the basis of a simple colorimetric assay.
In the present study, the SOS chromotest in a completely automated system
"Bioscreen C" was used to study interference between the adaptive and
SOS responses in E. coli. Our data indicate that there is an inhibitory effect
of the adaptive response on the SOS induction, as well as the negative
interference between two successive SOS responses, at a transcriptional level of
the SOS induction.
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