J Bacteriol, September 1998, p. 4547-4554, Vol. 180, No. 17
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
B from Listeria monocytogenes
and Its Role in Osmotolerance
Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska 68583-0919
Received 4 May 1998/Accepted 6 July 1998
Listeria monocytogenes is well known for its robust
physiology, which permits growth at low temperatures under conditions of high osmolarity and low pH. Although studies have provided insight
into the mechanisms used by L. monocytogenes to allay the
physiological consequences of these adverse environments, little is
known about how these responses are coordinated. In the studies
presented here, we have cloned the sigB gene and several rsb genes from L. monocytogenes, encoding
homologs of the alternative sigma factor
B and the
RsbUVWX proteins, which govern transcription of a general stress
regulon in the related bacterium Bacillus subtilis. The L. monocytogenes and B. subtilis sigB and
rsb genes are similar in sequence and physical
organization; however, we observed that the activity of
B in L. monocytogenes was uniquely
responsive to osmotic upshifting, temperature downshifting, and the
presence of EDTA in the growth medium. The magnitude of the response
was greatest after an osmotic upshift, suggesting a role for
B in coordinating osmotic responses in L. monocytogenes. A null mutation in the sigB gene led
to substantial defects in the ability of L. monocytogenes
to use betaine and carnitine as osmoprotectants. Subsequent
measurements of betaine transport confirmed that the absence of
B reduced the ability of the cells to accumulate
betaine. Thus,
B coordinates responses to a variety of
physical and chemical signals, and its function facilitates the growth
of L. monocytogenes under conditions of high osmotic
strength.
Journal Series paper 12219 of the Nebraska Agricultural
Experimental Station.
This article has been cited by other articles:
| Appl. Environ. Microbiol. | Infect. Immun. | Eukaryot. Cell |
|---|---|---|
| Mol. Cell. Biol. | J. Virol. | Microbiol. Mol. Biol. Rev. |
| ALL ASM JOURNALS |