Isolation of Rhodospirillum centenum Mutants Defective in Phototactic Colony Motility by Transposon Mutagenesis

Abstract

The purple photosynthetic bacterium Rhodospirillum centenum is capable of forming swarm colonies that rapidly migrate toward or away from light, depending on the wavelength of excitation. To identify components specific for photoperception, we conducted mini-Tn5-mediated mutagenesis and screened approximately 23,000 transposition events for mutants that failed to respond to either continuous illumination or to a step down in light intensity. A majority of the ca. 250 mutants identified lost the ability to form motile swarm cells on an agar surface. These cells appeared to contain defects in the synthesis or assembly of surface-induced lateral flagella. Another large fraction of mutants that were unresponsive to light were shown to be defective in the formation of a functional photosynthetic apparatus. Several photosensory mutants also were obtained with defects in the perception and transmission of light signals. Twelve mutants in this class were shown to contain disruptions in a chemotaxis operon, and five mutants contained disruptions of components unique to photoperception. It was shown that screening for photosensory defective R. centenumswarm colonies is an effective method for genetic dissection of the mechanism of light sensing in eubacteria.

Bacterial lateral flagella: an inducible flagella system

“…In contrast, polar flagellum defects in Aeromonas spp. or R. centenum do not induce constitutive lateral flagella formation (Jiang et al, 1998;Altarriba et al, 2003;Canals et al, 2006a), demonstrating that lateral flagella expression is still under its natural control, and suggesting that polar flagella do not interact with lateral flagella regulation.…”

“…In these two bacterial species, the polar and lateral flagella systems do not appear to share either structural or regulatory genes (Kirov, 2003;McCarter, 2004), whereas in Azospirillum spp. and R. centenum they may shared distinct structural and/or regulatory genes (Jiang et al, 1998;Scheludko et al, 1998;McClain et al, 2002). Moreover, the dual flagella systems in V. parahaemolyticus and V. alginolyticus also have different energy sources driving motility, as the polar flagellum is powered by the sodium motive force and the lateral flagella are driven by the proton motive force (Atsumi et al, 1992).…”

Light affects motility and infectivity of Agrobacterium tumefaciens

“…A phototactic response involves an oriented movement of a cell towards or away from a light source. An important distinction is that the direction of irradiation is not relevant for scotophobic or photokinetic responses, whereas it is a critical determinant in phototaxis (Jiang et al, 1998).…”

Roles of Chemosensory Pathways in Transient Changes in Swimming Speed of Rhodobacter sphaeroides Induced by Changes in Photosynthetic Electron Transport

“…Recent hybridization studies suggest that R. sphaeroides may have as many as 12 mcp homologs, expressed under different growth conditions (11a). Recent work with a related photosynthetic species, Rhodospirillum centenum, has shown that, in that species, there is only one common pathway signaling from chemoreceptors and photoreceptors to the motor (13,14,15).…”