Genome-Wide Screens Reveal New Gene Products That Influence Genetic Competence in Streptococcus mutans

Abstract

A network of genes and at least two peptide signaling molecules tightly control when becomes competent to take up DNA from its environment. Widespread changes in the expression of genes occur when is presented with competence signal peptides , including increased production of the alternative sigma factor, ComX, which activates late competence genes. Still, the way that gene products that are regulated by competence peptides influence DNA uptake and cellular physiology are not well understood. Here, we developed and employed comprehensive transposon mutagenesis of the genome with a screen to identify mutants that aberrantly expressed , coupled with transposon sequencing (Tn-seq) to gain a more thorough understanding of the factors modulating expression and progression to the competent state. The screens effectively identified genes known to affect competence, e.g. ,, ,, ,, ,, but disclosed an additional 20 genes that were not previously competence-associated. The competence phenotypes of mutants were characterized, including using fluorescence microscopy to determine at which stage the mutants were impaired for activation. Among the novel genes studied were those implicated in cell division, sensing of cell envelope stress, cell envelope biogenesis, and RNA stability. Our results provide a platform for determining the specific chemical and physical cues that are required for genetic competence in, while highlighting the effectiveness of using Tn-seq in to discover and study novel biological processes. acquires DNA from its environment by becoming genetically competent, a physiologic state triggered by cell-cell communication using secreted peptides. Competence is important for acquiring novel genetic traits and has a strong influence on the expression of virulence-associated traits of Here, we used transposon mutagenesis and genomic technologies to identify novel genes involved in competence development. In addition to identifying genes previously known to be required for expression, 20 additional genes were identified and characterized. The findings create opportunities to diminish the pathogenic potential of , while validating technologies that can rapidly advance our understanding of the physiology, biology and genetics of and related pathogens.

Disruption of l -Rhamnose Biosynthesis Results in Severe Growth Defects in Streptococcus mutans

“…While the identity of the sugar being transferred is not currently known, it is reminiscent of the activity of the glucosyltransferases RgpE and RgpH in S. mutans. Studies of RgpI have shown that it plays a role in comX-inducing peptide (XIP)-mediated activation of the alternative sigma factor comX (48). ComX, a protein that guides RNA polymerase to the promoters of late competence genes (49) and facilitates their transcription, is not activated in the absence of rgpI, rendering those strains nontransformable in defined medium containing XIP (48).…”

Genomewide Identification of Essential Genes and Fitness Determinants of Streptococcus mutans UA159

“…Tn-seq technologies have been applied in Streptococcus pneumoniae ( 11 ), Streptococcus pyogenes ( 17 ), and Streptococcus agalactiae ( 18 ). It is only recently that this approach has been applied to the study of S. mutans ( 19 ), with a focus on genetic competence.…”

The carbon catabolite repressor CcpA mediates optimal competence development in Streptococcus oligofermentans through post‐transcriptional regulation

“…Natural competence for DNA transformation is one of the main strategies employed by streptococci to acquire exogenous DNA for genetic diversity (Kreth et al , ; Croucher et al , ; Lin et al , ; Wholey et al , ; Underhill et al , ). First described in S. pneumoniae (Avery et al , ), natural competence has been found in more than 80 bacterial species to date, particularly in oral streptococci (Johnston et al , ; Khan et al , ; Salvadori et al , ; Shields et al , ). Internalization of extracellular DNA greatly contributes to the genomic plasticity of bacteria, but this also increases the risk of deleterious mutations and consumes energy for competence machinery synthesis (Croucher et al , ).…”