Abstract
Bacteria swim and swarm using rotating flagella that are driven by a membrane-spanning motor complex. Performance of the flagella motility apparatus is modulated by the chemosensory signal transduction system to allow navigation through physico-chemical gradients – a process that can be fine-tuned by the bacterial second messenger c-di-GMP. We have previously analysed the Pseudomonas putida signalling protein PP2258 that has the capacity to both synthesize and degrade c-di-GMP. A PP2258 null mutant displays reduced motility, implicating the c-di-GMP signal originating from this protein in control of P. putida motility. In Escherichia coli and Salmonella, the PilZ-domain protein YcgR mediates c-di-GMP responsive control of motility through interaction with the flagellar motors. Here we provide genetic evidence that the P. putida protein PP4397 (also known as FlgZ), despite low sequence homology and a different genomic context to YcgR, functions as a c-di-GMP responsive link between the signal arising from PP2258 and alterations in swimming and swarming motility in P. putida.
Highlights
Bacteria swim and swarm using rotating flagella that are driven by a membrane-spanning motor complex
We show that despite very limited amino acid sequence identity and different in vitro properties to those of YcgR, FlgZ/PP4397 lies downstream of PP2258 in c-di-GMP responsive motility control in P. putida and can be functionally replaced by YcgR in this process
Having established that PP4397 is co-ordinately regulated with genes of the flagella regulon, we addressed its involvement in c-di-GMP responsive control of flagella-mediated motility
Summary
Bacteria swim and swarm using rotating flagella that are driven by a membrane-spanning motor complex. In Escherichia coli and Salmonella, the PilZ-domain protein YcgR mediates c-di-GMP responsive control of motility through interaction with the flagellar motors. In the enterics Escherichia coli and Salmonella, the PilZ domain protein YcgR co-localizes with flagella and acts as a brake in response to c-di-GMP by interacting with components of the flagella motor[17,18,19]. In these organisms, the non-rotating part of the motor – the stator – is formed by membrane complexes of the MotA/MotB proteins that provide the ion-translocating channels that energise the rotor. The carboxy-PilZ domain of YcgR binds c-di-GMP with a 1:1 ratio and binding of c-di-GMP causes YcgR to adopt a more condensed conformation without altering its monomeric status[20], while it’s amino-terminal domain is involved with interactions with its targets – MotA, FliG and/or FliM – to result in reduced torque and motility[17,18,19]
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