title: The Lipopolysaccharide Lipid A Long-Chain Fatty Acid Is Important for Rhizobium leguminosarum Growth and Stress Adaptation in Free-Living and Nodule Environments.
abstract: Rhizobium bacteria live in soil and plant environments, are capable of inducing symbiotic nodules on legumes, invade these nodules, and develop into bacteroids that fix atmospheric nitrogen into ammonia. Rhizobial lipopolysaccharide (LPS) is anchored in the bacterial outer membrane through a specialized lipid A containing a very long-chain fatty acid (VLCFA). VLCFA function for rhizobial growth in soil and plant environments is not well understood. Two genes, acpXL and lpxXL, encoding acyl carrier protein and acyltransferase, are among the six genes required for biosynthesis and transfer of VLCFA to lipid A. Rhizobium leguminosarum mutant strains acpXL, acpXL-/lpxXL-, and lpxXL-were examined for LPS structure, viability, and symbiosis. Mutations in acpXL and lpxXL abolished VLCFA attachment to lipid A. The acpXL mutant transferred a shorter acyl chain instead of VLCFA. Strains without lpxXL neither added VLCFA nor a shorter acyl chain. In all strains isolated from nodule bacteria, lipid A had longer acyl chains compared with laboratory-cultured bacteria, whereas mutant strains displayed altered membrane properties, modified cationic peptide sensitivity, and diminished levels of cyclic β-glucans. In pea nodules, mutant bacteroids were atypically formed and nitrogen fixation and senescence were affected. The role of VLCFA for rhizobial environmental fitness is discussed.
authors.affiliation: 1 Complex Carbohydrate Research Center, University of Georgia, Athens 30602, U.S.A.|3 U.S. National Poultry Research Center, Agricultural Research Service, United States Department of Agriculture, Athens, GA 30605, U.S.A.
authors.forename: Dianna V
authors.initials: DV
authors.lastname: Bourassa
authors.affiliation: 1 Complex Carbohydrate Research Center, University of Georgia, Athens 30602, U.S.A.
authors.forename: Elmar L
authors.initials: EL
authors.lastname: Kannenberg
authors.affiliation: 2 Department of Plant and Soil Sciences and Delaware Biotechnology Institute, University of Delaware, Newark 19711, U.S.A.; and.
authors.forename: D Janine
authors.initials: DJ
authors.lastname: Sherrier
authors.affiliation: 3 U.S. National Poultry Research Center, Agricultural Research Service, United States Department of Agriculture, Athens, GA 30605, U.S.A.
authors.forename: R Jeffrey
authors.initials: RJ
authors.lastname: Buhr
authors.affiliation: 1 Complex Carbohydrate Research Center, University of Georgia, Athens 30602, U.S.A.
authors.forename: Russell W
authors.initials: RW
authors.lastname: Carlson
mesh_terms: D000222:Adaptation, Physiological; D005030:Ethylenes / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D008050:Lipid A / Q000737:chemistry / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation; D009995:Osmosis; D018532:Pisum sativum / Q000382:microbiology; D016961:Rhizobium leguminosarum / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure; D053204:Root Nodules, Plant / Q000382:microbiology* / Q000648:ultrastructure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013312:Stress, Physiological; D047071:beta-Glucans / Q000378:metabolism
chemical_list: D005030:Ethylenes; D005227:Fatty Acids; D008050:Lipid A; D008070:Lipopolysaccharides; D047071:beta-Glucans; C036216:ethylene; D005947:Glucose