Bacterial chemotaxis to xenobiotic chemicals and naturally-occurring analogs

• Chemoreceptors are more abundant and diverse in soil bacteria than in enteric bacteria.
• Bacteria have strategies to detect xenobiotics both directly and in response to their metabolism.
• Chemotaxis and biodegradation in soil bacteria are often coordinately regulated.
• Chemotaxis to xenobiotics may facilitate catabolic plasmid transfer and pathway evolution.
• Chemoreceptor sequence and domain structure are insufficient to predict their chemical ligands.

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. However, the strategies and receptors used by bacteria to sense chemicals are difficult to predict solely by bioinformatics, and much work is needed to uncover the range of chemicals detected and the specific functions of the numerous chemoreceptors present in catabolically versatile soil bacteria.

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