title: Identification of a divergent O-acetyltransferase gene oac 1b from Shigella flexneri serotype 1b strains.
abstract: Shigella flexneri is a leading cause of bacterial dysentery in developing countries. Among the 15 known serotypes, four (1b, 3a, 3b and 4b) contain a group 6 epitope due to an acetyl group connected to the O-2 position of rhamnose III on the tetrasaccharide structure of the lipopolysaccharide. O-acetyltransferase encoded by a bacteriophage, Sf6, mediates the acetylation reaction. We found that the oac gene in serotype 1b strains was very different from that in serotypes 3a, 3b and 4b strains and is herein after referred to as oac 1b which shares with oac 88%-89% identity at the DNA level and 85% identity at the protein level. Considering that S. flexneri strains of serotypes 1-5 share a recent common ancestry, the divergent oac 1b is more likely to have been obtained from outside S. flexneri than to have undergone rapid divergence from the oac gene in the other serotypes (3a, 3b and 4b) within S. flexneri. The cloned oac 1b gene was found to perform the same acetylation function as oac. Analysis of the genomic regions flanking oac 1b showed that it was present in a prophage on the chromosome and the organizational structure is different from that of phage Sf6. Additionally, phage conversion assay showed that serotype 1b cannot be generated by infecting serotype 1a strains with Sf6. We conclude that oac 1b was carried by a non-Sf6 phage and is uniquely present in serotype 1b.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Qiangzheng
authors.initials: Q
authors.lastname: Sun
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales , Sydney NSW 2052, Australia.
authors.forename: Ruiting
authors.initials: R
authors.lastname: Lan
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Wang
authors.affiliation: Branch for Enteric Disease Control and Prevention, Institute for Infectious Disease Control and Prevention, Henan Center for Disease Control and Prevention , Zhengzhou 450016, China.
authors.forename: Shengli
authors.initials: S
authors.lastname: Xia
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Yiting
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Branch for Enteric Disease Control and Prevention, Institute for Infectious Disease Control and Prevention, Henan Center for Disease Control and Prevention , Zhengzhou 450016, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Gansu Center for Disease Control and Prevention , Lanzhou 730000, China.
authors.forename: Deshan
authors.initials: D
authors.lastname: Yu
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Zhenjun
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Huaiqi
authors.initials: H
authors.lastname: Jing
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , China CDC, Beijing 102206, China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Xu
keywords: O-acetyltransferase; Shigella flexneri; serotype; serotype 1b