Pherotype Influences Biofilm Growth and Recombination in Streptococcus Pneumoniae

PLoS One. 2014 Mar 19;9(3):e92138. doi: 10.1371/journal.pone.0092138. eCollection 2014.

Abstract

In Streptococcus pneumoniae the competence-stimulating peptide (CSP), encoded by the comC gene, controls competence development and influences biofilm growth. We explored the influence of pherotype, defined by the two major comC allelic variants (comC1 and comC2), on biofilm development and recombination efficiency. Among isolates recovered from human infections those presenting comC1 show a higher capacity to form in vitro biofilms. The influence of pherotype on biofilm growth was confirmed by experiments with isogenic strains differing in their comC alleles. Biofilm architecture evaluated by confocal laser scanning microscopy showed that strains carrying comC1 form biofilms that are denser and thicker than those carrying the comC2 allele. Isogenic strains carrying the comC1 allele yielded more transformants than those carrying the comC2 allele in both planktonic and biofilm growth. Transformation assays with comC knockout strains show that ComD1 needs lower doses of the signaling peptide to reach the same biological outcomes. In contrast to mixed planktonic growth, within mixed biofilms inter-pherotype genetic exchange is less frequent than that occurring between bacteria of the same pherotype. Since biofilms are a major bacterial lifestyle, these observations may explain the genetic differentiation between populations with different pherotypes reported previously. Considering that biofilms have been associated with colonization our results suggest that strains carrying the comC1 allele may be more transmissible and more efficient at persisting in carriage. Both effects may help explain the higher prevalence of the comC1 allele in the pneumococcal population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism
  • Biofilms / growth & development*
  • Linear Models
  • Mutant Proteins / metabolism
  • Pheromones / metabolism*
  • Plankton / growth & development
  • Recombination, Genetic / genetics*
  • Streptococcus pneumoniae / genetics*
  • Streptococcus pneumoniae / physiology*
  • Transformation, Bacterial

Substances

  • Bacterial Proteins
  • Mutant Proteins
  • Pheromones
  • competence factor, Streptococcus

Grant support

Margarida Carrolo is supported research grants from Fundação para a Ciência e Tecnologia, Portugal (SFRH/BD/35854/2007 and SFRH/BPD/79310/2011). This work was partially supported by Fundação para a Ciência e Tecnologia, Portugal (PTDC/SAU-ESA/64888/2006, PTDC/BIA-MIC/119709/2010 and PTDC/EBB-EBI/113824/2009). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.