The pea nodule environment restores the ability of a Rhizobium leguminosarum lipopolysaccharide acpXL mutant to add 27-hydroxyoctacosanoic acid to its lipid A.
Members of the Rhizobiaceae contain 27-hydroxyoctacosanoic acid (27OHC(28:0)) in their lipid A. A Rhizobium leguminosarum 3841 acpXL mutant (named here Rlv22) lacking a functional specialized acyl carrier lacked 27OHC(28:0) in its lipid A, had altered growth and physiological properties (e.g., it was unable to grow in the presence of an elevated salt concentration [0.5% NaCl]), and formed irregularly shaped bacteroids, and the synchronous division of this mutant and the host plant-derived symbiosome membrane was disrupted. In spite of these defects, the mutant was able to persist within the root nodule cells and eventually form, albeit inefficiently, nitrogen-fixing bacteroids. This result suggested that while it is in a host root nodule, the mutant may have some mechanism by which it adapts to the loss of 27OHC(28:0) from its lipid A. In order to further define the function of this fatty acyl residue, it was necessary to examine the lipid A isolated from mutant bacteroids. In this report we show that addition of 27OHC(28:0) to the lipid A of Rlv22 lipopolysaccharides is partially restored in Rlv22 acpXL mutant bacteroids. We hypothesize that R. leguminosarum bv. viciae 3841 contains an alternate mechanism (e.g., another acp gene) for the synthesis of 27OHC(28:0), which is activated when the bacteria are in the nodule environment, and that it is this alternative mechanism which functionally replaces acpXL and is responsible for the synthesis of 27OHC(28:0)-containing lipid A in the Rlv22 acpXL bacteroids.
Vedam
Vinata
V
University of Georgia, Complex Carbohydrate Research Center, 315 Riverbend Rd., Athens, GA 30602, USA.
Kannenberg
Elmar
E
Datta
Anup
A
Brown
Dusty
D
Haynes-Gann
Janine G
JG
Sherrier
D Janine
DJ
Carlson
Russell W
RW
D000213:Acyl Carrier Protein / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D006880:Hydroxy Acids / Q000378:metabolism*; D008050:Lipid A / Q000737:chemistry / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D009154:Mutation; D018532:Pisum sativum / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology*; D016961:Rhizobium leguminosarum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D012965:Sodium Chloride / Q000633:toxicity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
C102838:AcpXL protein, Rhizobium; D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D006880:Hydroxy Acids; D008050:Lipid A; D008070:Lipopolysaccharides; C059845:27-hydroxyoctacosanoic acid; D012965:Sodium Chloride