Identification of horizontal gene transfer and recombination of PsaA gene in streptococcus mitis group.
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 species-specific 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.
Zhang
Qiao
Q
Institute of Respiratory Diseases, Xinqiao Hospital, Third Military Medical University, No. 183 Xinqiao Street, Chongqing 400037, China.
Ma
Qianli
Q
Su
Dan
D
Li
Qi
Q
Yao
Wei
W
Wang
Changzheng
C
D018829:Adhesins, Bacterial / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D022761:Gene Transfer, Horizontal; D008074:Lipoproteins / Q000737:chemistry / Q000235:genetics*; D010802:Phylogeny; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D034361:Streptococcus mitis / Q000145:classification / Q000235:genetics*; D009626:Terminology as Topic
D018829:Adhesins, Bacterial; D008074:Lipoproteins; C085000:PsaA protein, Streptococcus