All Seven comG Open Reading Frames Are Required for DNA Binding during Transformation of Competent Bacillus subtilis

Abstract

The seven proteins encoded by the comG operon ofBacillus subtilis exhibit similarity to gene products required for the assembly of type 4 pili and for the secretion of certain proteins in gram-negative bacteria. Although polar transposon insertions in comG result in the loss of transformability and in the failure of cells grown through the competence regimen to bind DNA, it was not known whether the ComG proteins are all required for competence. We have constructed strains missing each of these proteins individually and found that they are all nontransformable and fail to bind transforming DNA to the cell surface. The implications of these findings are discussed.

Cell surface localization and processing of the ComG proteins, required for DNA binding during transformation of Bacillus subtilis

“…Recently, we have found that ComEA is a DNA binding protein, with higher affinity for double-stranded than for single-stranded DNA (Provvedi and Dubnau, 1998). Mutants deficient in any of the ComG proteins also fail to bind DNA (Chung and Dubnau, 1998), although ComEA is still present in such mutants (Provvedi and Dubnau, 1998). In vitro experiments designed to detect DNA binding to the ComG proteins have yielded uniformly negative results (Provvedi and Dubnau, 1998).…”

“…Among the competence proteins with orthologues in the other competence systems are those encoded by the B. subtilis comG operon (Albano et al, 1989). This operon specifies seven gene products that are individually required for the binding of DNA to the competent cell Breitling and Dubnau, 1990;Chung and Dubnau, 1998). The ComG proteins belong to several families, each with members required for the assembly of pili and for the secretion of proteins across the outer membranes of certain Gram-negative bacteria, in addition to those needed for competence.…”

“…The remaining comG product, ComGF, is a small protein with a single predicted membrane-spanning segment near its N-terminus. It does not appear to possess a processing site, has no known orthologue and its role is unknown, although it is required for DNA binding to the competent cell surface (Chung and Dubnau, 1998).…”

Temporal competition between differentiation programs determines cell fate choice

“…Specifically, we determined how long it took, after initiation of ComK expression, for competence to reach the ability to take up extracellular DNA. As a marker for functional competence, we utilized the localization of the membrane protein ComGA to the cell pole, as part of the ATP-dependent complex required for uptake of extracellular DNA (Chung and Dubnau, 1998;Hahn et al, 2005). Furthermore, ComGA localization has also been suggested to participate in the blocking of chromosome replication during competence (Haijema et al, 2001).…”

Single cell analysis of gene expression patterns of competence development and initiation of sporulation in Bacillus subtilis grown on chemically defined media

“…Competence development is initiated when a threshold level of ComK is reached and comK auto-activation is triggered (Maamar and Dubnau 2005;Smits et al 2005b). ComK in turn activates the expression of the comG operon, which encodes factors required for the uptake of exogenous DNA from the environment (Chung and Dubnau 1998). Previously, it was shown that the promoter of the comG operon fused to the gfp gene is a good reporter to identify cells that have initiated competence development (Smits et al 2005b).…”