The NmpRSTU signaling system influences multicellular development and an oxygen utilization response in Myxococcus xanthus

Abstract

Myxococcus xanthus is an aerobic soil bacterium known for its complex social behaviors such as microbial predation and multicellular development. The mechanisms underlying these dynamic processes make M. xanthus an exceptional model for signal transduction systems. For example, when nutrients in the environment become scarce, M. xanthus develops multicellular fruiting bodies containing spores. Fruiting body development is highly dynamic and requires Type-IV pili (T4P) dependent motility. When a required gene, pilR, is deleted, M. xanthus cannot move or develop fruiting bodies. Recently, mutations in an oxygen-responsive multi-component signaling system called NmpRSTU were discovered that restore motility to this otherwise nonmotile ΔpilR strain. The first aim of my work was to characterize fruiting body development in mutant strains with restored motility to examine if development would also be restored. I found that although these strains clearly displayed motility, development was not restored. In other work, it was shown that the response regulator of the NmpRSTU system, NmpR, binds to the promoter region of several genes that may be important for oxygen utilization. One of these genes, mxan_5531, is predicted to encode an oxygen-binding protein called a hemerythrin. The second aim of my work was to purify and characterize MXAN_5531 to determine if it is a bona fide hemerythrin. I found that MXAN_5531 and three other predicted hemerythrins are functional in vitro.