The myxobacterium Sorangium cellulosum So ce26, the producer of the agriculturally important fungicide antibiotic soraphen A, displays coordinated gliding motility (swarming) on agar surfaces. The consequent failure to form detached colonies represents a major obstacle for microbiological and genetic studies, since single cells representing discrete genetic events cannot be reliably separated and propagated as clones. The MgIA protein, the product of the mglA gene, has been shown to be a central regulator of gliding motility and swarming in the related myxobacterium Myxococcus xanthus. We have cloned and sequenced a chromosomal locus from S. cellulosum So ce26 that shows similarity to the M. xanthus mglA locus. Insertional inactivation of the chromosomal copy of the S. cellulosum So ce26 mglA homolog resulted in a strain with a non-swarming colony phenotype. This strain is able to form distinct colonies presumably derived from single cells. This is the first report on the characterization of a genetic element of the gliding motility system in the myxobacterial suborder Sorangineae.