Regulation of Polar Flagellar Number by the flhF and flhG Genes in Vibrio alginolyticus

Abstract

The number and location of bacterial flagella vary with the species. The Vibrio alginolyticus cell has a single polar flagellum, which is driven by sodium ions. We selected mutants on the basis of reduced swarming ability on soft agar plates. Among them, we found two mutants with multiple polar flagella, and named them KK148 and NMB155. In Pseudomonas species, it is known that FlhF and FleN, which are FtsY and MinD homologs, respectively, are involved in regulation of flagellar placement and number, respectively. We cloned homologous genes of V. alginolyticus, flhF and flhG. KK148 cells had a nonsense mutation in flhG; cells expressing transgenic flhG recovered the swarming ability and had a reduced number of polar flagella. NMB155 cells did not have a mutation in either flhF or flhG. In wild-type cells, expression of flhF increased the number of polar flagella; in contrast, expression of flhG reduced both the number of polar flagella and the swarming ability. These results suggest that FlhG negatively regulates the number of polar flagella in V. alginolyticus. KK148 cells expressing both flhF and flhG exhibited fewer polar flagella and better swarming ability than KK148 cells expressing flhG alone, suggesting that FlhG acts with FlhF.

FlhF, a signal recognition particle-like GTPase, is involved in the regulation of flagellar arrangement, motility behaviour and protein secretion in Bacillus cereus

“…fleN (also referred to as flhG) plays a role in regulating the number of polar flagella in Pseudomonas aeruginosa and Vibrio spp. (Correa et al, 2005;Dasgupta et al, 2000;Kusumoto et al, 2006). flhF has been recognized to be necessary for the placement of flagella at a cell pole in Pseudomonas putida (Pandza et al, 2000) and P. aeruginosa (Murray & Kazmierczak, 2006), as well as for flagellation in Vibrio cholerae (Correa et al, 2005), Campylobacter jejuni (Hendrixson & DiRita, 2003) and Helicobacter pylori (Niehus et al, 2004).…”

Structural basis for the molecular evolution of SRP-GTPase activation by protein

“…The recent structure of the SRP-FtsY complex, together with biochemical implications, suggest that the distal end of the hairpin-like SRP RNA may be involved in this activation 18 . The third SRP-GTPase FlhF, together with the MinD-type protein YlxH (also known as FlhG, FleN, motR or MinD2), is essential for the placement and assembly of flagella 19 in many polar and peritrichous flagellated bacteria [20][21][22][23][24] . FlhF is required for the targeting of the first flagellar protein, FliF, to the cell pole 25 by a mechanism that is so far poorly understood.…”

The crystal structure of the third signal-recognition particle GTPase FlhF reveals a homodimer with bound GTP

“…FlhF associates with the plasma membrane (7), where it localizes at the cell poles (6). Loss of FlhF induces a number of changes, from reduced transcription of flagellar genes to a random arrangement of flagella and even to absent or diminished motility (6,(8)(9)(10)(11)(12)(13). In yeast two-hybrid screens, FlhF was shown to dimerize (10).…”