1887

Abstract

Natural competence for genetic transformation in is controlled by the ComCDE signal-transduction pathway. Together, ComD, a membrane histidine kinase, and ComE, its cognate response regulator, constitute a typical two-component regulatory system involved in sensing the -encoded competence-stimulating peptide (CSP). The operon is strongly upregulated when CSP reaches a critical threshold, probably to coordinate competence induction throughout the population. During a study of the early regulation of the operon, a mutation which resulted in increased -galactosidase production from a  : :  fusion was isolated. This mutation, which was characterized as a G→T change in the transcription terminator of the tRNA located immediately upstream of , is suggested to destabilize the terminator and to allow transcriptional readthrough of . Here, it is shown that, quite unexpectedly, the mutation confers reduced transformability. A series of experiments undertaken with the aim of understanding this surprising phenotype is described. Evidence is presented that increased basal-level expression of impedes both spontaneous and CSP-induced competence in . There is a discussion of how an increased concentration of ComD and/or ComE could affect competence development.

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2006-02-01
2019-10-14
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