Previous Article | Next Article ![]()
Appl Environ Microbiol, May 1998, p. 1708-1714, Vol. 64, No. 5
Department of Plant
Biology1 and
Department of Horticulture
and Crop Science,2 Ohio State University,
Columbus, Ohio 43210
Received 12 January 1998/Accepted 9 March 1998
The changes in motility, chemotactic responsiveness, and
flagellation of Rhizobium meliloti RMB7201, L5-30, and
JJ1c10 were analyzed after transfer of the bacteria to buffer with no
available C, N, or phosphate. Cells of these three strains remained
viable for weeks after transfer to starvation buffer (SB) but lost all motility within just 8 to 72 h after transfer to SB. The rates of
motility loss differed by severalfold among the strains. Each strain
showed a transient, two- to sixfold increase in chemotactic responsiveness toward glutamine within a few hours after transfer to
SB, even though motility dropped substantially during the same period.
Strains L5-30 and JJ1c10 also showed increased responsiveness to the
nonmetabolizable chemoattractant cycloleucine. Cycloleucine partially
restored the motility of starving cells when added after transfer and
prevented the loss of motility when included in the SB used for initial
suspension of the cells. Thus, interactions between chemoattractants
and their receptors appear to affect the regulation of motility in
response to starvation independently of nutrient or energy source
availability. Electron microscopic observations revealed that R. meliloti cells lost flagella and flagellar integrity during
starvation, but not as fast, nor to such a great extent, as the cells
lost motility. Even after prolonged starvation, when none of the cells
were actively motile, about one-third to one-half of the initially
flagellated cells retained some flagella. Inactivation of flagellar
motors therefore appears to be a rapid and important response of
R. meliloti to starvation conditions. Flagellar-motor
inactivation was at least partially reversible by addition of either
cycloleucine or glucose. During starvation, some cells appeared to
retain normal flagellation, normal motor activity, or both for
relatively long periods while other cells rapidly lost flagella, motor
activity, or both, indicating that starvation-induced regulation of
motility may proceed differently in various cell subpopulations.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Starvation-Induced Changes in Motility, Chemotaxis,
and Flagellation of Rhizobium meliloti
*
Corresponding author. Mailing address: Department of
Horticulture and Crop Science, 2021 Coffey Rd., Ohio State University, Columbus, OH 43210. Phone: (614) 292-9035. Fax: (614) 292-7162. E-mail:
bauer.7{at}osu.edu.
Ohio Agricultural Research and Development Center manuscript number
136-97.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»