Switches in macromolecular synthesis during induction of competence for transformation of Streptococcus sanguis.

Abstract

The induction of synchronous development of competence for genetic transformation in S. sanguis, by either endogenous or exogenous competence factor (CF), is manifested in the transient synthesis of a new set of at least 10 polypeptides, ranging from 14,000-51,000 in MW. Eight polypeptides (E14, E16, E24, E28, E32, E37, E44, E51) appear early, and 2 polypeptides (L34, L42) appear 5-10 min later. One of the newly synthesized early polypeptides, E16, is a component of the presynaptic complex containing single-stranded DNA that is produced in vivo upon uptake of native donor DNA. Concomitant with this induced synthesis of competence-specific polypeptides there is a net decrease in RNA and protein synthesis but no change in DNA synthesis; donor DNA-binding ability and transformability reach maxima during the phase of diminishing macromolecular synthesis. Subsequently, donor DNA-binding ability and transformability decay at disproportionate rates as cells return to the normal state of macromolecular synthesis within 1 generation. Coincident with the induction of competence, the synthesis of a new RNA transcript of high MW appears to be induced which continues during the restricted phase of total cellular RNA synthesis.