title: Rare Events of Intragenus and Intraspecies Horizontal Transfer of the 16S rRNA Gene.
abstract: Horizontal gene transfer (HGT) of operational genes has been widely reported in prokaryotic organisms. However, informational genes such as those involved in transcription and translation processes are very difficult to be horizontally transferred, as described by Woese's complexity hypothesis. Here, we analyzed all of the completed prokaryotic genome sequences (2,143 genomes) in the NCBI (National Center for Biotechnology Information) database, scanned for genomes with high intragenomic heterogeneity of 16S rRNA gene copies, and explored potential HGT events of ribosomal RNA genes based on the phylogeny, genomic organization, and secondary structures of the ribosomal RNA genes. Our results revealed 28 genomes with relatively high intragenomic heterogeneity of multiple 16S rRNA gene copies (lowest pairwise identity <98.0%), and further analysis revealed HGT events and potential donors of the heterogeneous copies (such as HGT from Chlamydia suis to Chlamydia trachomatis) and mutation events of some heterogeneous copies (such as Streptococcus suis JS14). Interestingly, HGT of the 16S rRNA gene only occurred at intragenus or intraspecies levels, which is quite different from the HGT of operational genes. Our results improve our understanding regarding the exchange of informational genes.
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, China.
authors.forename: Ren-Mao
authors.initials: RM
authors.lastname: Tian
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Cai
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, China.
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Zhang
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, China.
authors.forename: Hui-Luo
authors.initials: HL
authors.lastname: Cao
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, China boqianpy@ust.hk.
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Qian
mesh_terms: D002689:Chlamydia / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D018628:Gene Dosage; D022761:Gene Transfer, Horizontal; D019766:Genes, Archaeal; D005798:Genes, Bacterial; D014644:Genetic Variation; D020745:Genome, Archaeal; D016680:Genome, Bacterial; D009154:Mutation; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D046968:Thermoanaerobacter / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: 16S rRNA genes; accumulation of substitutions; horizontal gene transfer; intragenomic heterogeneity