title: Genetic diversity and features analysis of type VI secretion systems loci in avian pathogenic Escherichia coli by wide genomic scanning.
abstract: Avian pathogenic Escherichia coli (APEC) strains frequently cause extra-intestinal infections and significant economic losses. Recent studies revealed that the type VI secretion system (T6SS) is involved in APEC pathogenesis. Here we provide the first evidence of three distinguishable and conserved T6SS loci in APEC genomes. In addition, we present the prevalence and comparative genomic analysis of these three T6SS loci in 472 APEC isolates. The prevalence of T6SS1, T6SS2 and T6SS3 loci were 14.62% (69/472), 2.33% (11/472) and 0.85% (4/472) positive in the APEC collections, respectively, and revealed that >85% of the strains contained T6SS loci which consisted of the virulent phylogenetic groups D and B2. Comprehensive analysis showed prominent characteristics of T6SS1 locus, including wildly prevalence, rich sequence diversity, versatile VgrG islands and excellent expression competence in various E. coli pathotypes. Whereas the T6SS2 locus infatuated with ECOR groups B2 and sequence conservation, of which are only expressed in meningitis E. coli. Regrettably, the T6SS3 locus was encoded in negligible APEC isolates and lacked several key genes. An in-depth analysis about VgrG proteins indicated that their COG4253 and gp27 domain were involved in the transport of putative effector islands and recognition of host cells respectively, which revealed that VgrG proteins played an important role in functions formation of T6SS.
authors.affiliation: Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Jiale
authors.initials: J
authors.lastname: Ma
authors.forename: Min
authors.initials: M
authors.lastname: Sun
authors.forename: Yinli
authors.initials: Y
authors.lastname: Bao
authors.forename: Zihao
authors.initials: Z
authors.lastname: Pan
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Chengping
authors.initials: C
authors.lastname: Lu
authors.forename: Huochun
authors.initials: H
authors.lastname: Yao
mesh_terms: D000818:Animals; D058947:Bacterial Secretion Systems / Q000235:genetics*; D001482:Base Composition; D001483:Base Sequence; D001921:Brain / Q000382:microbiology; D004372:Ducks / Q000382:microbiology*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000235:genetics / Q000662:veterinary*; D014644:Genetic Variation; D011201:Poultry Diseases / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D058947:Bacterial Secretion Systems
keywords: Avian pathogenic Escherichia coli; Diversity; Genomic; Prevalence; Type VI secretion system; VgrG protein