Bacterial signaling and motility: Sure bets
- University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
The IX International Conference on Bacterial Locomotion and Signal Transduction (BLAST IX) was held from 14 to 19 January 2007 in Laughlin, NV, a town in the Mojave Desert on the Nevada-Arizona border near old Route 66 and along the banks of the Colorado River. This area is a home to rattlesnakes, sagebrush, abandoned gold mines, and compulsive gamblers. What better venue could scientists possibly dream of for a professional meeting? So there they were, about 190 scientists gathered in the Aquarius Casino Resort, the largest hotel and casino in Laughlin, discussing the latest advances in the field. Aside from a brief excursion to an abandoned gold mine and a dinner cruise on the Colorado River, the scientists focused on nothing but their data and hypotheses, in spirited arguments and rebuttals, and outlined their visions and future plans in a friendly and open environment. The BLAST IX program was dense, with nearly 50 talks and over 90 posters. For that reason, this meeting report will not attempt to be comprehensive; instead it will first provide general background information on the central topics of the meeting and then highlight only a few talks that were of special interest to us and hopefully to the wider scientific community. We will also attempt to articulate some of the future directions or perspectives to the best of our abilities. The best known and understood bacterial motility mechanism is swimming powered by flagella. The rotation of bacterial flagella drives this form of bacterial movement in an aqueous environment. A bacterial flagellum consists of a helical filament attached to the cell body through a complex structure known as the hook-basal body, which drives flagellar rotation. The essential components of the basal body are the MotA-MotB motor-stator proteins bound to the cytoplasmic membrane. These stator proteins interact with proteins that comprise the supramembrane and cytoplasmic rings, which are components of the motor imbedded in the cytoplasmic membrane. The interaction causes the supramembrane and cytoplasmic rings to rotate along with the flagellar filaments. The energy for flagellar rotation comes from proton motive force or other ions, especially sodium in marine bacteria, which generate an electrochemical gradient across the cell membrane. Three proteins, FliM, FliN, and FliG, located at the base of the motor act as switches that control the direction of flagellar rotation. As exemplified by the enteric bacteria Escherichia coli and Salmonella enterica serovar Typhimurium, changes in the direction of flagellar rotation affect the swimming behavior of the bacterial cell. Counterclockwise (CCW) rotation of the flagella causes the flagellar filaments to form a bundle that pushes the cell forward in a 'run.' In contrast, clockwise (CW) rotation causes the flagellar bundle to fly apart, and the cell tumbles to reorient to a new direction for the ensuing run upon the return of CCW rotation. The interchanging pattern of CCW and CW rotations produces a random walk, composed of relatively long runs with occasional direction changes or turns. By modulating the lengths of the runs or the frequency of tumbling, bacteria can regulate their motile behavior to move in a desirable direction. Many bacteria can also move on surfaces. Except for flagellum-driven swarming motility, all the other forms of known bacterial surface movement involve no flagella. The flagellum-independent surface motility, known as gliding, is observed in cyanobacteria, Mycoplasma species, Cytophaga-Flexibacterium species, and Myxococcus species. Without a doubt, the most thoroughly studied model gliding bacterium is Myxococcus xanthus, which also serves as a prokaryotic model for developmental biology due to its ability to develop multicellular fruiting bodies. M. xanthus cells use gliding motility both to hunt for food during vegetative growth and to aggregate during fruiting body formation. When nutrients are present, groups of cells or swarms propagate and move outward like hunting wolf packs in search of additional macromolecules or prey. Upon starvation, cells aggregate at discrete foci to form mounds and then macroscopic fruiting bodies, each with hundreds of thousands of cells. The rod-shaped cells in the fruiting bodies eventually morph into spherical spores that are metabolically inactive and partially resistant to desiccation and temperature. When nutrients become available, spores can germinate and reenter the vegetative cell cycle. Two talks highlighted in this meeting review will tackle the mysteries of the gliding motility of M. xanthus in greater detail. In addition to M. xanthus, Caulobacter crescentus has extensively been investigated as a bacterial model of cell differentiation and development.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1045265
- Journal Information:
- Journal of Bacteriology, Vol. 190, Issue 6; ISSN 0021-9193
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
60 APPLIED LIFE SCIENCES
BACTERIA
CELL CYCLE
CELL DIFFERENTIATION
CELL MEMBRANES
CHEMORECEPTORS
CONFORMATIONAL CHANGES
CYANOBACTERIA
ESCHERICHIA COLI
ESTERASES
HISTIDINE
LIFE CYCLE
MYCOPLASMA
PHOSPHATASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
PROTEINS
ROTATION
SPORES
TRANSCRIPTION FACTORS