Swimming and Behavior in Purple Non-Sulfur Bacteria

Abstract

Many species of purple bacteria swim, and they direct that swimming towards carbon and nitrogen sources, light and/or oxygen using a complex set of chemosensory pathways. The review will illustrate how genomics, molecular biology, biochemistry, behavioral analysis and in vivo imaging have been used to try and dissect the pathways, identifying common features and the variations on those themes. Work on two purple species in particular has provided insights into these complexities. Rhodobacter (Rba.) sphaeroides shows that different pathways can be localized to different parts of the cell, revealing a complex intracellular organization allowing cells to tune their responses to metabolic need, while in Rhodospirillum centenum not all genes annotated as chemosensory turn out to be involved in chemotaxis, rather they are involved in regulating development. The complexity and variation of the sensory pathways identifi ed to date in the purple bacteria illustrate the modifi cation of the inputs and outputs of the related systems, refl ecting the different growth environments and requirements of the different species.