title: The plant pathogen Ralstonia solanacearum needs aerotaxis for normal biofilm formation and interactions with its tomato host.
abstract: Ralstonia solanacearum is a soilborne pathogen that causes bacterial wilt of diverse plant species. To locate and infect host plant roots R. solanacearum needs taxis, the ability to move toward more favorable conditions. However, the specific signals that attract this pathogen were unknown. One candidate is aerotaxis, or energy taxis, which guides bacteria toward optimal intracellular energy levels. The R. solanacearum genome encodes two putative aerotaxis transducers. Cloned R. solanacearum aer1 and aer2 genes restored aerotaxis to an Escherichia coli aer mutant, demonstrating that both genes encode heterologously functional aerotaxis transducers. Site-directed mutants lacking aer1, aer2, or both aer1 and aer2 were significantly less able to move up an oxygen gradient than the wild-type parent strain; in fact, the aerotaxis of the aer mutants was indistinguishable from that of a completely nonmotile strain. Tomato plants inoculated with either the aer2 or the aer1/aer2 mutant had slightly delayed wilt disease development. Furthermore, the aer1/aer2 double mutant was significantly impaired in the ability to rapidly localize on tomato roots compared to its wild-type parent. Unexpectedly, all nonaerotactic mutants formed thicker biofilms on abiotic surfaces than the wild type. These results indicate that energy taxis contributes significantly to the ability of R. solanacearum to locate and effectively interact with its host plants.
authors.affiliation: Department of Plant Pathology, University of Wisconsin-Madison, 1630 Linden Dr., Madison, WI 53706, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Yao
authors.forename: Caitilyn
authors.initials: C
authors.lastname: Allen
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D002352:Carrier Proteins / Q000235:genetics; D002633:Chemotaxis / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D017353:Gene Deletion; D005816:Genetic Complementation Test; D036341:Intercellular Signaling Peptides and Proteins; D018551:Solanum lycopersicum / Q000382:microbiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology; D043368:Ralstonia solanacearum / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: C108679:Aer protein, E coli; D002352:Carrier Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D036341:Intercellular Signaling Peptides and Proteins