Identification of horizontal gene transfer and recombination of PsaA gene in streptococcus mitis group

Abstract

Pneumococcal surface adhesin A (psaA) gene is universally confirmed as one of the Streptococcus pneumoniae adhesion genes, but it is disputed whether the psaA gene is a Streptococcus pneumoniae speciesspecific gene. In the present study, the presence of the psaA gene in 34 streptococcus mitis group isolates was identified by the PCR approach and a comparison of sequencing PCR products (Streptococcus pneumoniae R6 as the control strain). Also, the evolutionary scenarios of these psaA genes in these streptococcus mitis group isolates were analyzed by a phylogenetic tree based on the housekeeping genes (sodA and rnpB) and psaA genes. As a result, a high degree of conservation of open reading frame sequences in all six Streptococcus pneumoniae strains (100% similarity) and in the other species of the streptococcus mitis group (92.6-100% similarity) was revealed. Further genetics research based on housekeeping genes and psaA gene phylogenies showed that the psaA gene was of vertical inheritance only in Streptococcus pneumoniae; however, high-frequency horizontal psaA gene transfer and recombination occurred in the other species of the streptococcus mitis group. These findings confirmed that the psaA gene was not a Streptococcus pneumoniae species-specific gene, and high-frequency HGT and recombination events may explain the presence of the psaA gene in the other species of the streptococcus mitis group.

Phylogenetic relationship and virulence inference of Streptococcus Anginosus Group: curated annotation and whole-genome comparative analysis support distinct species designation

“…Five of the 55 virulence proteins newly identified within SAG are inferred to be adhesion proteins including: a fibronectin binding protein (Fbp54), important in adhesion for S. gordonii [48], a S. pneumoniae and S. mitis surface adhesion protein (PsaA) [49], a laminin-binding protein important for adherence in GBS [50], pullulanase protein important in Streptococcus adhesion [51] and Streptococcus enolase a strong plasminogen-binding protein [52]. …”

Identification of Streptococcus pneumoniae and other Mitis streptococci: importance of molecular methods

“…The psaA gene, encoding pneumococcal surface antigen A (PsaA), which constitutes a manganese ABCtype transporter is commonly found among S. pneumoniae and was proposed as a target for PCR-based detection [71], showing good performance on collections of S. pneumoniae and other Mitis streptococci [55,72,73]. However, also this gene turned out to be present among some isolates of Mitis streptococci [26,66,74,75]. Yet another proposed virulenceassociated target, the cpsA (wzg) gene, which is typically the first gene in the cps operon, responsible for the biosynthesis of capsular polysaccharide [76], is absent among some nonserotypable pneumococci, as discussed above (see Immunological methods).…”

Genome Mining and Comparative Analysis of Streptococcus intermedius Causing Brain Abscess in a Child

“…Binding was found to activate an immune response causing cytokine buildup followed by tissue damage and onset of brain abscess formation [17]. Other adhesion proteins were also detected such as surface protein ( psa A) [26], enolase ( eno ) for plasminogen binding, and pullulanase ( pul A) [27]. The invasive properties of the 17 isolates were associated with a complete Streptococcus Invasion locus ( sil ) system and an internalin A homologous gene ( inlA ).…”