Affiliation:
1. Department of Biomedical Sciences, Oregon State University, Corvallis, Oregon 97331
Abstract
ABSTRACT
Vibrio tubiashii
, a causative agent of severe shellfish larval disease, produces multiple extracellular proteins, including a metalloprotease (VtpA), as potential virulence factors. We previously reported that VtpA is toxic for Pacific oyster (
Crassostrea gigas
) larvae. In this study, we show that extracellular protease production by
V. tubiashii
was much reduced by elevated salt concentrations, as well as by elevated temperatures. In addition,
V. tubiashii
produced dramatically less protease in minimal salts medium supplemented with glucose or sucrose as the sole carbon source than with succinate. We identified a protein that belongs to the TetR family of transcriptional regulators, VtpR, which showed high homology with
V. cholerae
HapR. We conclude that VtpR activates VtpA production based on the following: (i) a VtpR-deficient
V. tubiashii
mutant did not produce extracellular proteases, (ii) the mutant showed reduced expression of a
vtpA-lacZ
fusion, and (iii) VtpR activated
vtpA-lacZ
in a
V. cholerae
heterologous background. Moreover, we show that VtpR activated the expression of an additional metalloprotease gene (
vtpB
). The deduced VtpB sequence showed high homology with a metalloprotease, VhpA, from
V. harveyi
. Furthermore, the
vtpR
mutant strain produced reduced levels of extracellular hemolysin, which is attributed to the lower expression of the
V. tubiashii
hemolysin genes (
vthAB
). The VtpR-deficient mutant also had negative effects on bacterial motility and did not demonstrate toxicity to oyster larvae. Together, these findings establish that the
V. tubiashii
VtpR protein functions as a global regulator controlling an array of potential virulence factors.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
31 articles.
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