Pherotypes of pneumococcal strains co-existing in healthy children

Area of Science:

• Microbiology
• Genetics
• Population Biology

Background:

• Genetic diversity in Streptococcus pneumoniae is primarily driven by horizontal gene transfer.
• Bacterial competence, essential for transformation, is regulated by quorum-sensing via competence stimulating peptide (CSP).
• Two major CSP pherotypes, CSP-1 and CSP-2, exist in S. pneumoniae, influencing inter-strain interactions.

Purpose of the Study:

• To investigate the distribution of CSP pherotypes in S. pneumoniae strains from healthy children.
• To determine if CSP pherotypes impact the co-colonization dynamics of S. pneumoniae.
• To assess the role of pherotypes in potential speciation or fratricide mechanisms.

Main Methods:

• Sequencing of the comC locus encoding CSP in S. pneumoniae strains from nasopharyngeal samples.
• Analysis of multiple S. pneumoniae strains co-colonizing the same host simultaneously.
• Statistical comparison of observed pherotype distribution in co-colonizing strains against expected probabilities.

Main Results:

• Five distinct comC alleles were identified, corresponding to CSP-1 (62.7%) and CSP-2 (37.3%) pherotypes.
• The observed distribution of CSP pherotypes in co-colonizing S. pneumoniae strains did not significantly differ from random probability.
• No evidence of pherotype-based restriction on co-colonization was found.

Conclusions:

• Pherotype does not act as a barrier to co-colonization by different Streptococcus pneumoniae strains in healthy children.
• The findings challenge theories suggesting pherotypes create barriers for gene transfer or promote fratricide.
• Horizontal gene transfer and genetic diversity in S. pneumoniae may occur more freely across pherotypes than previously hypothesized.