Function of Mg1 Proteins in Gliding in Myxococcus

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The long range goal of this project is to understand the mechanism of surface translocation, or gliding, in myxobacteria. The survival of a diverse group of environmentally important organisms, including myxobacteria, cytophaga, cyanobacteria, and Beggiotoa, depends upon their ability to glide. In this project, Myxococcus xanthus will be used as a model to understand gliding because it is genetically well-characterized. One gene, mglA, is essential for gliding; the focus of this project will be on how MglA protein interacts with other motility components. Since mglA is the only gene common to the two known genetically-identified systems, A and S, that control gliding, MglA protein may affect expression of A- and S-gliding genes. The first aim will therefore be to isolate and characterize reporter gene (lacZ) insertions in A- and S-motility genes and determine if their transcription is altered in an mgl- strain. Another goal will be to use mutagenesis to probe the functional domains of MglA by identifying mglA mutants that show aberrant gliding. Suppressor experiments have also been designed to identify genes encoding proteins that interact with MglA. One mutant has already been identified that suppresses the mglA defect, and the corresponding gene will be cloned to determine if it encodes a gliding protein that interacts with MglA. %%% Bacteria need to be able to move from one place to another in order to survive. One of the most intriguing, and least understood, mechanisms of bacterial motility is the phenomenon of gliding on solid substrata. The field is complicated by the likelihood that the gliding mechanisms employed by one group of gliding bacteria may not be the same as those employed by other groups. In myxobacteria, gliding is crucial not only to enable the bacteria to find food, but also to enable the bacteria to undergo a developmental transition from the vegetative gliding bacterium form to a sporogenic "fruiting body." There are two almost independent motility systems, termed "A" ("adventurous") and "S" ("social"). S-motility requires cell-to-cell proximity for movement to occur, and is known to involve at least 12 distinct genes. A-motility does not require cell-cell contact, and is controlled by at least 22 genes. Wild-type myxococci exhibit both A+ and S+ motility. A mutation in one of the A or S genes abolishes only the A or S type of motility. Both of these mechanisms seem to involve regulation of the same basic motility machinery. In addition, there are other genes, termed "frz" genes, which affect the rate at which cells reverse direction while gliding. However, there is a single genetic locus, mglA, for which a mutation abolishes both A and S type motility, resulting in totally nonmotile bacteria. The proposed studies of this pivotal gene are likely to shed new light on the mechanism of gliding in myxococci.