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Applied and Environmental Microbiology, April 1999, p. 1710-1720, Vol. 65, No. 4
Center for Marine Biotechnology and
Biomedicine, Scripps Institution of Oceanography, University of
California, San Diego, La Jolla, California
92093-0202,1 and Calgene LLC Monsanto,
Davis, California 956162
Received 28 October 1998/Accepted 3 February 1999
There is considerable evidence correlating the production of
increased proportions of membrane unsaturated fatty acids (UFAs) with
bacterial growth at low temperatures or high pressures. In order to
assess the importance of UFAs to microbial growth under these
conditions, the effects of conditions altering UFA levels in the
psychrotolerant piezophilic deep-sea bacterium Photobacterium profundum SS9 were investigated. The fatty acids produced by
P. profundum SS9 grown at various temperatures and
pressures were characterized, and differences in fatty acid composition
as a function of phase growth, and between inner and outer membranes, were noted. P. profundum SS9 was found to exhibit enhanced
proportions of both monounsaturated (MUFAs) and polyunsaturated (PUFAs)
fatty acids when grown at a decreased temperature or elevated pressure. Treatment of cells with cerulenin inhibited MUFA but not PUFA synthesis
and led to a decreased growth rate and yield at low temperature and
high pressure. In addition, oleic acid-auxotrophic mutants were
isolated. One of these mutants, strain EA3, was deficient in the
production of MUFAs and was both low-temperature sensitive and
high-pressure sensitive in the absence of exogenous 18:1 fatty acid.
Another mutant, strain EA2, produced little MUFA but elevated levels of
the PUFA species eicosapentaenoic acid (EPA; 20:5n-3). This mutant grew slowly but was not low-temperature sensitive or
high-pressure sensitive. Finally, reverse genetics was employed to
construct a mutant unable to produce EPA. This mutant, strain EA10, was
also not low-temperature sensitive or high-pressure sensitive. The
significance of these results to the understanding of the role of UFAs
in growth under low-temperature or high-pressure conditions is discussed.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Monounsaturated but Not Polyunsaturated Fatty
Acids Are Required for Growth of the Deep-Sea Bacterium
Photobacterium profundum SS9 at High Pressure and
Low Temperature
*
Corresponding author. Mailing address: Center for
Marine Biotechnology and Biomedicine, Scripps Institution of
Oceanography, 4405 Hubbs Hall, University of California, San Diego,
8604 La Jolla Shores Dr., La Jolla, CA 92093-0202. Phone: (619)
534-5233. Fax: (619) 534-7313. E-mail: dbartlett{at}ucsd.edu.
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