Transcriptional Organization of the Region Encoding the Synthesis of the Flagellar Filament in
            <i>Pseudomonas fluorescens</i>

bMotility plays an essential role in bacterial fitness and colonization in the plant environment, since it favors nutrient acquisition and avoidance of toxic substances, successful competition with other microorganisms, the ability to locate the preferred hosts, access to optimal sites within them, and dispersal in the environment during the course of transmission. In this work, we have observed that the mutation of the flagellar master regulatory gene, fleQ, alters bacterial surface motility and biosurfactant production, uncovering a new type of motility for Pseudomonas syringae pv. tomato DC3000 on semisolid surfaces. We present evidence that P. syringae pv. tomato DC3000 moves over semisolid surfaces by using at least two different types of motility, namely, swarming, which depends on the presence of flagella and syringafactin, a biosurfactant produced by this strain, and a flagellumindependent surface spreading or sliding, which also requires syringafactin. We also show that FleQ activates flagellum synthesis and negatively regulates syringafactin production in P. syringae pv. tomato DC3000. Finally, it was surprising to observe that mutants lacking flagella or syringafactin were as virulent as the wild type, and only the simultaneous loss of both flagella and syringafactin impairs the ability of P. syringae pv. tomato DC3000 to colonize tomato host plants and cause disease. Motility plays a pivotal role in the spreading of bacteria across surfaces and colonization, contributing to the formation of structured communities called biofilms (1). Efficient bacterial motility under diverse environmental conditions, from liquid to semisolid and solid surfaces, is achieved by flagellum-dependent swimming and swarming or flagellum-independent twitching, gliding, nonsocial gliding, and sliding (2, 3, 4). Swimming is a flagellum-driven motility observed in bacteria moving through liquids or semisolid media, such as low-percentage agar (0.2% to 0.4%). Twitching is a slow cell movement on surfaces mediated by the extension and retraction of type IV pili (5). Gliding, a surface movement extensively studied in myxobacteria, does not require flagella or pili but involves focal adhesion complexes, cell surfaceassociated complexes that anchor the bacterium to a substrate and might act as a motor (6). Sliding is a passive form of surface spreading by expansion that is powered by the outward pressure of bacterial growth and facilitated by compounds that reduce friction between cells and surfaces (3). Sliding or spreading by expansion has been observed in a diverse group of bacteria, such as mycobacteria, Bacillus subtilis, Vibrio cholerae, Serratia marcescens, Pseudomonas aeruginosa, or Legionella pneumophila (7-12), in which a strong correlation between sliding and production of surfactants has been established. Furthermore, sliding is easily mistaken for swarming motility and can occur when flagella are disrupted in bacteria that normally would swarm (7,8,13,14). Swarming is a rapid and coordinated movement of bacterial popul...

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“…2 and 3). The results presented here corroborate that flagellar biosynthesis is differently regulated in diverse Pseudomonas strains (71).…”

Section: Resultssupporting

confidence: 78%

FleQ Coordinates Flagellum-Dependent and -Independent Motilities in Pseudomonas syringae pv. tomato DC3000

Nogales

Vargas

Farias

et al. 2015

Appl Environ Microbiol

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“…2A). By this approach, we would be able to detect amplification only where the mRNA is polycistronic for the adjacent genes probed (35). We observed that no amplification occurred only between 3= fliF L and 5= lafA2, and between 3= lafA2 and 5= lafA1 (see Fig.…”

Section: Resultsmentioning

confidence: 78%

“…S4): two of the reactions amplified fragments of the coding sequence of each contiguous gene (positive control), while the third amplified a fragment encompassing the intergenic region between the target genes (35).…”

Section: Methodsmentioning

confidence: 99%

Transcriptional Control of the Lateral-Flagellar Genes of Bradyrhizobium diazoefficiens

et al. 2017

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Bradyrhizobium diazoefficiens, a soybean N 2 -fixing symbiont, possesses a dual flagellar system comprising a constitutive subpolar flagellum and inducible lateral flagella. Here, we analyzed the genomic organization and biosynthetic regulation of the lateral-flagellar genes. We found that these genes are located in a single genomic cluster, organized in two monocistronic transcriptional units and three operons, one possibly containing an internal transcription start site. Among the monocistronic units is blr6846, homologous to the class IB master regulators of flagellum synthesis in Brucella melitensis and Ensifer meliloti and required for the expression of all the lateral-flagellar genes except lafA2, whose locus encodes a single lateral flagellin. We therefore named blr6846 lafR (lateral-flagellar regulator). Despite its similarity to two-component response regulators and its possession of a phosphorylatable Asp residue, lafR behaved as an orphan response regulator by not requiring phosphorylation at this site. Among the genes induced by lafR is flbT L , a class III regulator. We observed different requirements for FlbT L in the synthesis of each flagellin subunit. Although the accumulation of lafA1, but not lafA2, transcripts required FlbT L , the production of both flagellin polypeptides required FlbT L . Moreover, the regulation cascade of this lateral-flagellar regulon appeared to be not as strictly ordered as those found in other bacterial species.IMPORTANCE Bacterial motility seems essential for the free-living style in the environment, and therefore these microorganisms allocate a great deal of their energetic resources to the biosynthesis and functioning of flagella. Despite energetic costs, some bacterial species possess dual flagellar systems, one of which is a primary system normally polar or subpolar, and the other is a secondary, lateral system that is produced only under special circumstances. Bradyrhizobium diazoefficiens, an N 2 -fixing symbiont of soybean plants, possesses dual flagellar systems, including the lateral system that contributes to swimming in wet soil and competition for nodulation and is expressed under high energy availability, as well as under requirement for high torque by the flagella. The structural organization and transcriptional regulation of the 41 genes that comprise this secondary flagellar system seem adapted to adjust bacterial energy expenditures for motility to the soil's environmental dynamics.KEYWORDS Bradyrhizobium, flagella, expression, lafR, flbT, FlbT, LafR F lagellum-driven swimming motility-a characteristic trait of many bacterial species-is essential for the colonization of diverse niches in environments such as seas, freshwaters, sediments, soils, and the organs of plant or animal hosts. This form of bacterial locomotion requires the propulsion provided by flagella, as well as a guidance system mediated by chemotaxis (1).Flagella are complex organelles formed by three main structures: a basal body that anchors the flagellum to the cell envelope...

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“…Several of these genes in F113 have been previously analyzed [44,45] and regulation of flagella synthesis requires the master regulatory gene fleQ [46]. Besides these genes, F113 chromosome harbors another 41 kb flagella locus containing 40 CDSs (PSF113_0738-PSF113_0782), which is not present in any other Pseudomonas genome, with the exception of P. extremaustralis (Figure 4A).…”

Section: Resultsmentioning

confidence: 99%

Genome sequence reveals that Pseudomonas fluorescens F113 possesses a large and diverse array of systems for rhizosphere function and host interaction

et al. 2013

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BackgroundPseudomonas fluorescens F113 is a plant growth-promoting rhizobacterium (PGPR) isolated from the sugar-beet rhizosphere. This bacterium has been extensively studied as a model strain for genetic regulation of secondary metabolite production in P. fluorescens, as a candidate biocontrol agent against phytopathogens, and as a heterologous host for expression of genes with biotechnological application. The F113 genome sequence and annotation has been recently reported.ResultsComparative analysis of 50 genome sequences of strains belonging to the P. fluorescens group has revealed the existence of five distinct subgroups. F113 belongs to subgroup I, which is mostly composed of strains classified as P. brassicacearum. The core genome of these five strains is highly conserved and represents approximately 76% of the protein-coding genes in any given genome. Despite this strong conservation, F113 also contains a large number of unique protein-coding genes that encode traits potentially involved in the rhizocompetence of this strain. These features include protein coding genes required for denitrification, diterpenoids catabolism, motility and chemotaxis, protein secretion and production of antimicrobial compounds and insect toxins.ConclusionsThe genome of P. fluorescens F113 is composed of numerous protein-coding genes, not usually found together in previously sequenced genomes, which are potentially decisive during the colonisation of the rhizosphere and/or interaction with other soil organisms. This includes genes encoding proteins involved in the production of a second flagellar apparatus, the use of abietic acid as a growth substrate, the complete denitrification pathway, the possible production of a macrolide antibiotic and the assembly of multiple protein secretion systems.

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Transcriptional Organization of the Region Encoding the Synthesis of the Flagellar Filament in Pseudomonas fluorescens

Cited by 16 publications

References 26 publications

FleQ Coordinates Flagellum-Dependent and -Independent Motilities in Pseudomonas syringae pv. tomato DC3000

FleQ Coordinates Flagellum-Dependent and -Independent Motilities in Pseudomonas syringae pv. tomato DC3000

Transcriptional Control of the Lateral-Flagellar Genes of Bradyrhizobium diazoefficiens

Genome sequence reveals that Pseudomonas fluorescens F113 possesses a large and diverse array of systems for rhizosphere function and host interaction

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