Conditional requirement of SglT for type IV pili function and S-motility in .

Myxobacteria exhibit complex social behaviors such as predation, outer membrane exchange and fruiting body formation. These behaviors depend on coordinated movements of cells on solid surfaces that involve social (S) motility. S-motility is powered by extension-retraction cycles of type 4 pili (Tfp) and exopolysaccharides (EPS) that provide a matrix for group cellular movement. Here, we characterized a new class of S-motility mutants in . These mutants have a distinctive phenotype: they lack S-motility even though they produce pili and EPS and the phenotype is temperature-sensitive. The point mutations were mapped to a single locus, MXAN_3284, named . Similar to mutants, mutants are hyperpiliated and, strikingly, the temperature-sensitive phenotype is caused by null mutations. Our results indicate that SglT plays a critical role in Tfp function associated with pilus retraction and that the block in pili retraction is caused by a Tfp assembly defect in the absence of SglT at high-temperature growth.