fleN , a Gene That Regulates Flagellar Number in Pseudomonas aeruginosa

Abstract

The single polar flagellum of Pseudomonas aeruginosa plays an important role in the pathogenesis of infection by this organism. However, regulation of the assembly of this organelle has not been delineated. In analyzing the sequence available at the Pseudomonas genome database, an open reading frame (ORF), flanked by flagellar genes flhF and fliA, that coded for a protein (280 amino acids) with an ATP-binding motif at its N terminus was found. The ORF was inactivated by inserting a gentamicin cassette in P. aeruginosa PAK and PAO1. The resulting mutants were nonmotile on motility agar plates, but under a light microscope they exhibited random movement and tumbling behavior. Electron microscopic studies of the wild-type and mutant strains revealed that the mutants were multiflagellate, with three to six polar flagella per bacterium as rather than one as in the wild type, indicating that this ORF was involved in regulating the number of flagella and chemotactic motility in P. aeruginosa. The ORF was named fleN. Flagella serve primarily as locomotory organelles in flagellated bacterial species. They have also been implicated in biofilm development in Pseudomonas aeruginosa and Escherichia coli (24,26) and in the pathogenesis of infections by P. aeruginosa, Campylobacter jejuni, Helicobacter pylori, and Vibrio cholerae (23,25). The bacterial flagellum is a complex structure requiring more than 40 genes for its assembly (18). Over the years, significant progress has been made in identifying various flagellar structural and regulatory genes, elucidating the composition of flagellar substructures, and understanding the mechanisms of its assembly in a number of bacterial species, including E. coli, Salmonella enterica serovar Typhimurium (1,18,22), and Caulobacter crescentus (28,38). Work is in progress to elucidate the pathway of flagellar assembly in the pathogens P. aeruginosa, V. cholerae, and H. pylori.Most flagellated bacterial species have extracellular flagella; exceptions are spirochetes such as pathogenic Treponema pallidum and Borrelia burgdorferi, which have flagella implanted in the periplasmic space. In some cases, extracellular flagella are covered by a sheath, as in V. cholerae and H. pylori (23). The distribution of flagella may be monotrichous polar as in P. aeruginosa (14) and V. cholerae (39) or peritrichous (5 to 10 flagella) as in E. coli and Salmonella serovar Typhimurium (18). Flagellar number, a characteristic feature of each species, is successfully maintained over the generations, but nothing is known about the genes and the mechanisms which contribute to its regulation. In a recent model proposed for Salmonella, the number of flagellar filaments has been linked to the cell cycle (2).A major goal of our laboratory is to gain an insight into the biogenesis pathway of the flagellum of P. aeruginosa. The published information from our laboratory and elsewhere (5,6,29,33) indicates that the system deviates from the well-described enteric model (18). It has certain similarities to the Caulobacter (...

Genome‐wide identification of tolerance mechanisms toward p‐coumaric acid in Pseudomonas putida

“…The deletion of this gene in P. aeruginosa has been shown to alter the single polar flagella localization, affecting the motility of the cells (Dasgupta, Arora, & Ramphal, 2000). Even though some genes of the flagella systems have been identified in the tolerance toward toluene in the strain P. putida DOT‐T1E, their function in the resistance is not clear, since it does not seem to be related to the cells motility (Ramos et al, 2002).…”

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

“…The involvement of fleN/flhG, flhF and swrAA in the regulation of the number and/or position of flagella in different organisms (Calvio et al, 2005;Correa et al, 2005;Dasgupta et al, 2000;Hendrixson & DiRita, 2003;Kusumoto et al, 2006;Niehus et al, 2004;Pandza et al, 2000) prompted us to evaluate whether homologues of such genes were present in B. cereus. In silico analysis was performed on the B. cereus ATCC 14579 genome with the ERGO Genome and Discovery System (Overbeek et al, 2003) from Integrated Genomics and the BacMap Bacterial Genomes Atlas (Stothard et al, 2005).…”

“…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).…”

Cyclic diguanosine monophosphate represses bacterial flagella synthesis by interacting with the Walker A motif of the enhancer-binding protein FleQ

“…Previously reported data indicate that FleN is a FleQ antiactivator. Flagella gene expression is high in an fleN background (12,14).…”

“…Mutations in fleN (PA1454) lead to an up-regulation of flagella gene expression and a smalldown-regulation of biofilm genes (7,12). The expression of fleN is under the control of FleQ.…”