Hybrid Two-Component Sensors for Identification of Bacterial Chemoreceptor Function.

Soil bacteria adapt to diverse and rapidly changing environmental conditions by sensing and responding to environmental cues using a variety of sensory systems. Two-component systems are a widespread type of signal transduction system present in all three domains of life and typically are comprised of a sensor kinase and a response regulator. Many two-component systems function by regulating gene expression in response to environmental stimuli.

Bacterial chemotaxis to xenobiotic chemicals and naturally-occurring analogs.

The study of chemotaxis to xenobiotic chemicals in soil bacteria has revealed that the core mechanism for transduction of chemotactic signals is conserved. Responses to chemicals degraded by specialized catabolic pathways are often coordinately regulated with degradation genes, and in some cases auxiliary processes such as transport are integrated into the sensory process. In addition, degradation genes and associated chemotaxis genes carried on transmissible plasmids may facilitate the dissemination and evolution of catabolic and sensory systems.

Integration of chemotaxis, transport and catabolism in Pseudomonas putida and identification of the aromatic acid chemoreceptor PcaY.

Aromatic and hydroaromatic compounds that are metabolized through the β-ketoadipate catabolic pathway serve as chemoattractants for Pseudomonas putida F1. A screen of P. putida F1 mutants, each lacking one of the genes encoding the 18 putative methyl-accepting chemotaxis proteins (MCPs), revealed that pcaY encodes the MCP required for metabolism-independent chemotaxis to vanillate, vanillin, 4-hydroxybenzoate, benzoate, protocatechuate, quinate, shikimate, as well as 10 substituted benzoates that do not serve as growth substrates for P.

Cytosine chemoreceptor McpC in Pseudomonas putida F1 also detects nicotinic acid.

Soil bacteria are generally capable of growth on a wide range of organic chemicals, and pseudomonads are particularly adept at utilizing aromatic compounds. Pseudomonads are motile bacteria that are capable of sensing a wide range of chemicals, using both energy taxis and chemotaxis. Whilst the identification of specific chemicals detected by the ≥26 chemoreceptors encoded in Pseudomonas genomes is ongoing, the functions of only a limited number of Pseudomonas chemoreceptors have been revealed to date.

Pseudomonas putida F1 has multiple chemoreceptors with overlapping specificity for organic acids.

Previous studies have demonstrated that Pseudomonas putida strains are not only capable of growth on a wide range of organic substrates, but also chemotactic towards many of these compounds. However, in most cases the specific chemoreceptors that are involved have not been identified. The complete genome sequences of P.

Taxis of Pseudomonas putida F1 toward phenylacetic acid is mediated by the energy taxis receptor Aer2.

The phenylacetic acid (PAA) degradation pathway is a widely distributed funneling pathway for the catabolism of aromatic compounds, including the environmental pollutants styrene and ethylbenzene. However, bacterial chemotaxis to PAA has not been studied. The chemotactic strain Pseudomonas putida F1 has the ability to utilize PAA as a sole carbon and energy source.