The cell surface-associated intercellular C-signal induces behavioral changes in individual Myxococcus xanthus cells during fruiting body morphogenesis

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Abstract
Fruiting body formation in Myxococcus xanthus depends on ordered changes in cell movements from swarming to aggregation in response to starvation. We show that appropriately starved individual cells change behavior during fruiting body formation. Specifically, from the time of initiation of aggregation, individual wild-type cells began to move with increased gliding speeds, the duration of the mean gliding interval increased, and the stop frequency decreased whereas the duration of the mean stop interval and the reversal frequency remained unchanged. Mutants lacking the cell surface-associated, intercellular C-signal (csgA mutants) failed to aggregate. Likewise, appropriately starved individual csgA cells did not change their behavior during development. In the absence of other cell–cell interactions, the motility defect of individual csgA cells was corrected in a time- and concentration-dependent manner after C-signaling was reestablished by exogenous MalE-CsgA protein. The C-signal-induced stimulation of motility depended on the cytoplasmic Frz signal transduction system. We propose that C-signal instructs cells to move with high speed and low stop and reversal frequencies into aggregation centers during development.