title: Flagellar motility contributes to the invasion and survival of Aeromonas hydrophila in Anguilla japonica macrophages.
abstract: The interaction between pathogenic bacteria and the host phagocytes is complicated. It is generally believed that only obligate intracellular pathogens can invade and survive in host phagocytes. In this study, we revealed that the pathogenic Aeromonas hydrophila B11 can also invade and survive in the macrophages of its host Anguilla japonica in vitro. To further investigate the mechanisms of A. hydrophila invasion and survival in host macrophages, a mini-Tn10 transposon mutagenesis system was used to generate an insertion mutant library by cell conjugation between the donor Escherichia coli Sm10 (pLOFKm) and the recipient A. hydrophila B11. Out of 465 individual colonies, 13 mutants impaired in survival within macrophages were selected, and the mutant BM116 was the most seriously impaired strain. Molecular analysis showed that an ORF of approximately 1335 bp (GenBank accession numbers JQ974982) of the mutant BM116 was inserted by mini-Tn10. This ORF putatively encodes a deduced 445 amino acids protein that displays the highest identity (99.6%) with the flagellar hook protein FlgE of A. hydrophila subsp. hydrophila ATCC 7966. The biological characteristics of the wild-type B11, the mutant B116 and the complemented strain were investigated. The results reveal that the flagella of the mutant BM116 was absent and that these mutant bacteria exhibited defective motility, adhesion, and invasion and survival in host macrophages when compared with the wild type and the complemented strain. These findings indicate that flgE is required for flagellum biogenesis in A. hydrophila and that flagellar motility is required for A. hydrophila invasion and survival in the macrophages of its host. Our findings provide an important new understanding of the nonintracellular pathogenic bacteria invasion and survival in host phagocytes and the interactions between the pathogens and their host.
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China.
authors.forename: Yingxue
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China.
authors.forename: Guifang
authors.initials: G
authors.lastname: Lin
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China.
authors.forename: Wenbo
authors.initials: W
authors.lastname: Chen
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China.
authors.forename: Bei
authors.initials: B
authors.lastname: Huang
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China.
authors.forename: Wenshu
authors.initials: W
authors.lastname: Huang
authors.affiliation: Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, P.R. China, Jimei University, Xiamen, Fujian 361021, PR China; Fisheries College, Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Xiamen, Fujian 361021, PR China. Electronic address: yanqp@jmu.edu.cn.
authors.forename: Qingpi
authors.initials: Q
authors.lastname: Yan
mesh_terms: D016980:Aeromonas hydrophila / Q000235:genetics / Q000502:physiology*; D000704:Analysis of Variance; D000811:Anguilla; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D015139:Blotting, Southern; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D004926:Escherichia coli; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology*; D005407:Flagella / Q000502:physiology; D016905:Gram-Negative Bacterial Infections / Q000662:veterinary*; D054884:Host-Pathogen Interactions; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004251:DNA Transposable Elements; C097681:FlgE protein, Bacteria
keywords: Aeromonas hydrophila; Flagella; Phagocytes; Survival