A flagellin gene from the fish pathogen Vibrio anguillarum was cloned, sequenced, and mutagenized. The DNA sequence suggests that the tiaA gene encodes a 40.1-kDa protein and is a single transcriptional unit. A polar mutation and four in-frame deletion mutations (180 hp deleted from the 5' end of the gene, 153 bp deleted from the 3' end of the gene, a double deletion of both the 180- and 153-bp deletions, and 942 bp deleted from the entire gene) were made. Compared with the wild type, all mutants were partially motile, and a shortening of the flagellum was seen by electron microscopy. Wild-type phenotypes were regained when the mutations were transcomplemented with the flaA gene. Protein analysis indicated that the flaA gene corresponds to a 40- kDa protein and that the flagellum consists of three additional flagellin proteins with molecular masses of 41, 42, and 45 kDa. N-terminal sequence analysis confirmed that the additional proteins were flagellins with N termini that are 82 to 88% identical to the N terminus of FlaA. Virulence studies showed that the N terminal deletion, the double deletion, and the 942-bp deletion increased the 50% lethal dose between 70- and 700-fold via immersion infection, whereas infection via intraperitoneal injection showed no loss in virulence. In contrast, the polar mutant and the carboxy-terminal deletion mutant showed approximately a 104-fold increase in the 50% lethal dose by both immersion and intraperitoneal infection. In summary, FlaA is needed for crossing the fish integument and may play a role in virulence after invasion of the host.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Microbiology
Research Field:	Bacteriology
Objective Division:	Health
Objective Group:	Clinical health
Objective Field:	Clinical health not elsewhere classified
UTAS Author:	O'Toole, R (Dr Ronan O'Toole)
ID Code:	95807
Year Published:	1996
Web of Science® Times Cited:	563
Deposited By:	Medicine
Deposited On:	2014-10-08
Last Modified:	2014-10-08
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