Comparative analysis of the Streptococcus pneumoniae competence development in vitro versus in vivo during pneumonia-derived sepsis.

Introduction: The Streptococcus pneumoniae (pneumococcus) competence regulon is well-known for regulating genetic transformation but is also important for virulence. Some pneumococcal strains can enter a transient competent state for genetic transformation in an optimized competence-inducing medium when the threshold level of the peptide pheromone competence stimulating peptide is attained; upregulating the expression of three distinct phases of "early", "late" and "delayed" competence genes. Recently, we discovered that pneumococcus can naturally enter a prolonged competent state during acute pneumonia in mice. However, mechanisms driving competence development during host infection are rarely examined, and a direct comparison between in vitro and in vivo competence induction has not been performed.

Methods: We conducted a comparative gene expression analysis of pneumococcal competence development in vitro versus in vivo during pneumonia-derived sepsis in mice. We examined existing RNA-Seq data and performed validation using RNA obtained from an independent replicate experiment.

Results and discussion: Our analysis revealed both similarities and differences in the expression of "early", "late", and "delayed" competence between in vitro versus during pneumonia-derived sepsis. Our results may reveal new aspects of pneumococcal competence biology.