title: An acpXL mutant of Rhizobium leguminosarum bv. phaseoli lacks 27-hydroxyoctacosanoic acid in its lipid A and is developmentally delayed during symbiotic infection of the determinate nodulating host plant Phaseolus vulgaris.
abstract: Rhizobium leguminosarum is a Gram-negative bacterium that forms nitrogen-fixing symbioses with compatible leguminous plants via intracellular invasion and establishes a persistent infection within host membrane-derived subcellular compartments. Notably, an unusual very-long-chain fatty acid (VLCFA) is found in the lipid A of R. leguminosarum as well as in the lipid A of the medically relevant pathogens Brucella abortus, Brucella melitensis, Bartonella henselae, and Legionella pneumophila, which are also able to persist within intracellular host-derived membranes. These bacterial symbionts and pathogens each contain a homologous gene region necessary for the synthesis and transfer of the VLCFA to the lipid A. Within this region lies a gene that encodes the specialized acyl carrier protein AcpXL, on which the VLCFA is built. This study describes the biochemical and infection phenotypes of an acpXL mutant which lacks the VLCFA. The mutation was created in R. leguminosarum bv. phaseoli strain 8002, which forms symbiosis with Phaseolus vulgaris, a determinate nodulating legume. Structural analysis using gas chromatography and mass spectrometry revealed that the mutant lipid A lacked the VLCFA. Compared to the parent strain, the mutant was more sensitive to the detergents deoxycholate and dodecyl sulfate and the antimicrobial peptide polymyxin B, suggesting a compromise to membrane stability. In addition, the mutant was more sensitive to higher salt concentrations. Passage through the plant restored salt tolerance. Electron microscopic examination showed that the mutant was developmentally delayed during symbiotic infection of the host plant Phaseolus vulgaris and produced abnormal symbiosome structures.
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd., Athens, GA 30602, USA.
authors.forename: Dusty B
authors.initials: DB
authors.lastname: Brown
authors.forename: Yu-Chu
authors.initials: YC
authors.lastname: Huang
authors.forename: Elmar L
authors.initials: EL
authors.lastname: Kannenberg
authors.forename: D Janine
authors.initials: DJ
authors.lastname: Sherrier
authors.forename: Russell W
authors.initials: RW
authors.lastname: Carlson
mesh_terms: D000213:Acyl Carrier Protein / Q000172:deficiency* / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000633:toxicity; D001426:Bacterial Proteins / Q000235:genetics; D002849:Chromatography, Gas; D003840:Deoxycholic Acid / Q000633:toxicity; D003902:Detergents / Q000633:toxicity; D006880:Hydroxy Acids / Q000032:analysis*; D008050:Lipid A / Q000737:chemistry*; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D027805:Phaseolus / Q000382:microbiology*; D011112:Polymyxin B / Q000633:toxicity; D016961:Rhizobium leguminosarum / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012967:Sodium Dodecyl Sulfate / Q000633:toxicity; D013559:Symbiosis; D014774:Virulence
chemical_list: C102838:AcpXL protein, Rhizobium; D000213:Acyl Carrier Protein; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003902:Detergents; D006880:Hydroxy Acids; D008050:Lipid A; D003840:Deoxycholic Acid; C059845:27-hydroxyoctacosanoic acid; D012967:Sodium Dodecyl Sulfate; C028913:dodecyl sulfate; D011112:Polymyxin B