title: Chemotaxis signaling systems in model beneficial plant-bacteria associations.
abstract: Beneficial plant-microbe associations play critical roles in plant health. Bacterial chemotaxis provides a competitive advantage to motile flagellated bacteria in colonization of plant root surfaces, which is a prerequisite for the establishment of beneficial associations. Chemotaxis signaling enables motile soil bacteria to sense and respond to gradients of chemical compounds released by plant roots. This process allows bacteria to actively swim towards plant roots and is thus critical for competitive root surface colonization. The complete genome sequences of several plant-associated bacterial species indicate the presence of multiple chemotaxis systems and a large number of chemoreceptors. Further, most soil bacteria are motile and capable of chemotaxis, and chemotaxis-encoding genes are enriched in the bacteria found in the rhizosphere compared to the bulk soil. This review compares the architecture and diversity of chemotaxis signaling systems in model beneficial plant-associated bacteria and discusses their relevance to the rhizosphere lifestyle. While it is unclear how controlling chemotaxis via multiple parallel chemotaxis systems provides a competitive advantage to certain bacterial species, the presence of a larger number of chemoreceptors is likely to contribute to the ability of motile bacteria to survive in the soil and to compete for root surface colonization.
authors.affiliation: Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA.
authors.forename: Birgit E
authors.initials: BE
authors.lastname: Scharf
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hynes
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, USA. galexan2@utk.edu.
authors.forename: Gladys M
authors.initials: GM
authors.lastname: Alexandre
mesh_terms: D001419:Bacteria / Q000235:genetics; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D044822:Biodiversity; D002633:Chemotaxis / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology; D010944:Plants / Q000378:metabolism* / Q000382:microbiology*; D058441:Rhizosphere; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins
keywords: Flagella; Motility; Nitrogen fixation; Rhizosphere; Signal transduction; Symbiosis