title: Two functional type VI secretion systems in avian pathogenic Escherichia coli are involved in different pathogenic pathways.
abstract: Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. The VgrG protein, a core component and effector of T6SS, has been demonstrated to perform diverse functions. The N-terminal domain of VgrG protein is a homologue of tail fiber protein gp27 of phage T4, which performs a receptor binding function and determines the host specificity. Based on sequence analysis, we found that two putative T6SS loci exist in the genome of the avian pathogenic Escherichia coli (APEC) strain TW-XM. To assess the contribution of these two T6SSs to TW-XM pathogenesis, the crucial clpV clusters of these two T6SS loci and their vgrG genes were deleted to generate a series of mutants. Consequently, T6SS1-associated mutants presented diminished adherence to and invasion of several host cell lines cultured in vitro, decreased pathogenicity in duck and mouse infection models in vivo, and decreased biofilm formation and bacterial competitive advantage. In contrast, T6SS2-associated mutants presented a significant decrease only in the adherence to and invasion of mouse brain microvascular endothelial cell (BMEC) line bEnd.3 and brain tissue of the duck infection model. These results suggested that T6SS1 was involved in the proliferation of APEC in systemic infection, whereas VgrG-T6SS2 was responsible only for cerebral infection. Further study demonstrated that VgrG-T6SS2 was able to bind to the surface of bEnd.3 cells, whereas it did not bind to DF-1 (chicken embryo fibroblast) cells, which further proved the interaction of VgrG-T6SS2 with the surface of BMECs.
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Jiale
authors: J
authors: Ma
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Yinli
authors: Y
authors: Bao
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Min
authors: M
authors: Sun
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Wenyang
authors: W
authors: Dong
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Zihao
authors: Z
authors: Pan
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Wei
authors: W
authors: Zhang
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China.
authors: Chengping
authors: C
authors: Lu
authors: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China yaohch@njau.edu.cn.
authors: Huochun
authors: H
authors: Yao
mesh_terms: D000818:Animals; D058947:Bacterial Secretion Systems / Q000235:genetics*; D018441:Biofilms / Q000254:growth & development; D001921:Brain / Q000382:microbiology; D002460:Cell Line; D002642:Chick Embryo; D002645:Chickens / Q000382:microbiology; D004372:Ducks / Q000382:microbiology; D042783:Endothelial Cells / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics*; D004927:Escherichia coli Infections / Q000235:genetics* / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D011817:Rabbits; D037521:Virulence Factors / Q000235:genetics
chemical_list: D058947:Bacterial Secretion Systems; D029968:Escherichia coli Proteins; D037521:Virulence Factors