title: Mechanism for transfer of transposon Tn2010 carrying macrolide resistance genes in Streptococcus pneumoniae and its effects on genome evolution.
abstract: OBJECTIVE
  The objective of this study was to identify the mechanism responsible for the horizontal transfer of transposon Tn2010 in Streptococcus pneumoniae, and the genomic alterations introduced by the transfer process.
  
  
  METHODS
  Tn2010 was identified using PCR in 15 clinical isolates of S. pneumoniae with erythromycin resistance. S. pneumoniae and Enterococcus faecalis isolates were used as recipient cells in mating and transformation experiments to test the conjugative transferability and transformability of Tn2010. Whole-genome sequencing was used to assess the effects of the Tn2010 transfer on recipient genomes. The biological cost of the horizontal acquisition of Tn2010 and additional genomic changes was investigated by growth competition experiments.
  
  
  RESULTS
  Tn2010 was transformed at a frequency of 3 × 10(-7) transformants per cfu, whereas no transconjugants were detected using S. pneumoniae or E. faecalis as recipient cells. Genome analysis showed that many other recombinations were scattered throughout the genome of the transformants in addition to transposon Tn2010. The transformants demonstrated a negligible fitness cost compared with the wild-type strain.
  
  
  CONCLUSIONS
  Tn2010 tended to be transferred by transformation rather than conjugation in S. pneumoniae, and the spread of Tn2010 could have a profound effect on the evolution of the genome. The acquisition of Tn2010 with negligible fitness cost may facilitate spread of the transposon.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Major Diseases in Children and National Key Discipline of Pediatrics, Ministry of Education, Beijing Pediatric Research Institute, Beijing Children's Hospital, Capital Medical University, Beijing, China.
authors.forename: Kaihu
authors.initials: K
authors.lastname: Yao
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Major Diseases in Children and National Key Discipline of Pediatrics, Ministry of Education, Beijing Pediatric Research Institute, Beijing Children's Hospital, Capital Medical University, Beijing, China.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute of Clinical Pharmacology, Peking University First Hospital, Beijing, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Clinical Pharmacology, Peking University First Hospital, Beijing, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lv
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China Beijing Key Laboratory of Microbial Drug Resistance and Resistome, Beijing, China fengj@im.ac.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Feng
mesh_terms: D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D011995:Recombination, Genetic; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D018942:Macrolides
keywords: fitness cost; recombination; transformation