ISSN:
0886-1544
Schlagwort(e):
swarming
;
gliding
;
cooperative motility
;
cell density effects
;
pili
;
Life and Medical Sciences
;
Cell & Developmental Biology
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Biologie
,
Medizin
Notizen:
The coordinated movement of many cells - a process called swarming - permits myxobacteria to spread rapidly over a surface. We have investigated the mechanism of swarming in Myxococcus xanthus by making time-lapse motion pictures and by measuring the dependence of cell movement and spreading rate on the concentration of cells. Motion pictures of spreading zones showed that spreading resulted from motility, not growth, and that a swarm spread outward by establishing a loose reticulum of cells, then later filling it in. The spreading rate of wildtype strains was found to be highly dependent on cell density, increasing about 8-fold as the cell density was increased from 2.5 to 200 units. Mutants swarmed if they possessed only the A-motile component (A+S-) or only the S-motile component (A-S+) of wild type (A+S+); their spreading rate increased with cell density but was always less than A+S+. Individual A+S+, A+S-, and A-S+ cells executed typical gliding movements and (when moving) progressed at approximately the same speed, as if A and S motility were different ways of engaging the same gliding machine. Photographic studies of an A-S+ strain showed that cells moved only if they were separated by less than approximately one cell length from each other. This provided further evidence that pili, which are present on A+S+ and A-S+ cells and which extend about one cell length, could be responsible for switching on movement in S-motile cells, and presumably in wild type as well.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/cm.970030304
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