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.
Institute of Respiratory Diseases, Xinqiao Hospital, Third Military Medical University, No. 183 Xinqiao Street, Chongqing 400037, China.
Qiao
Q
Zhang
Qianli
Q
Ma
Dan
D
Su
Qi
Q
Li
Wei
W
Yao
Changzheng
C
Wang
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