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Appl. Environ. Microbiol., Apr 1995, 1551-1554, Vol 61, No. 4
KH Nealson, DP Moser and DA Saffarini
Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically
at the expense of many different electron acceptors and is often found in
abundance at redox interfaces in nature. Such redox interfaces are often
characterized by very strong gradients of electron acceptors resulting from
rapid microbial metabolism. The coincidence of S. putrefaciens abundance
with environmental gradients prompted an examination of the ability of MR-1
to sense and respond to electron acceptor gradients in the laboratory. In
these experiments, taxis to the majority of the electron acceptors that S.
putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron
acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite,
elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter
was very weak and nitrate and nitrite respiration was normal in the
presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1
revealed that several electron acceptors that could not be used for
anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56,
which was unable to respire nitrite, showed normal taxis to nitrite, as
well as the inhibition of taxis to other electron acceptors by nitrite.
These results indicate that electron acceptor taxis in S. putrefaciens does
not conform to the paradigm established for Escherichia coli and several
other bacteria. Carbon chemotaxis was also unusual in this organism: of all
carbon compounds tested, the only positive response observed was to formate
under anaerobic conditions.
Copyright © 1995, American Society for Microbiology
Anaerobic Electron Acceptor Chemotaxis in Shewanella putrefaciens
Center for Great Lakes Studies, University of Wisconsin--Milwaukee, Milwaukee, Wisconsin 53204
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