Affiliation:
1. Bacteriology Group, International Centre for Genetic Engineering and Biotechnology, 34012 Trieste, Italy
Abstract
ABSTRACT
Bacterial strains belonging to
Burkholderia cepacia
can be human opportunistic pathogens, plant pathogens, and plant growth promoting and have remarkable catabolic activity.
B. cepacia
consists of several genomovars comprising what is now known as the
B. cepacia
complex. Here we report the quorum-sensing system of a genomovar I onion rot type strain ATCC 25416. Quorum sensing is a cell-density-dependent regulatory response which involves the production of
N
-acyl homoserine lactone (HSL) signal molecules. The
cep
locus has been inactivated in the chromosome, and it has been shown that CepI is responsible for the biosynthesis of an
N
-hexanoyl HSL (C
6
-HSL) and an
N
-octanoyl HSL (C
8
-HSL) and that the
cep
locus regulates protease production as well as onion pathogenicity via the expression of a secreted polygalacturonase. A
cep
-
lacZ
-based sensor plasmid has been constructed and used to demonstrate that CepR responded to C
6
-HSL with only 15% of the molar efficiency of C
8
-HSL, that a
cepR
knockout mutant synthesized 70% less HSLs, and that CepR responded best towards long-chain HSLs. In addition, we also report the cloning and characterization of the stationary-phase sigma factor gene
rpoS
of
B. cepacia
ATCC 25416. It was established that quorum sensing in
B. cepacia
has a negative effect on
rpoS
expression as determined by using an
rpoS
-
lacZ
transcriptional fusion; on the other hand,
rpoS
-null mutants displayed no difference in the accumulation of HSL signal molecules.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
65 articles.
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