title: Phosphatidylcholine levels of peanut-nodulating Bradyrhizobium sp. SEMIA 6144 affect cell size and motility.
abstract: Phosphatidylcholine, the major phospholipid in eukaryotes, is found in rhizobia and in many other bacteria interacting with eukaryotic hosts. Phosphatidylcholine has been shown to be required for a successful interaction of Bradyrhizobium japonicum USDA 110 with soybean roots. Our aim was to study the role of bacterial phosphatidylcholine in the Bradyrhizobium-peanut (Arachis hypogaea) symbiosis. Phospholipid N-methyltransferase (Pmt) and minor phosphatidylcholine synthase (Pcs) activities were detected in crude extracts of the peanut-nodulating strain Bradyrhizobium sp. SEMIA 6144. Our results suggest that phosphatidylcholine formation in Bradyrhizobium sp. SEMIA 6144 is mainly due to the phospholipid methylation pathway. Southern blot analysis using pmt- and pcs-probes of B. japonicum USDA 110 revealed a pcs and multiple pmt homologues in Bradyrhizobium sp. SEMIA 6144. A pmtA knockout mutant was constructed in Bradyrhizobium sp. SEMIA 6144 that showed a 50% decrease in the phosphatidylcholine content in comparison with the wild-type strain. The mutant was severely affected in motility and cell size, but formed wild-type-like nodules on its host plant. However, in coinoculation experiments, the pmtA-deficient mutant was less competitive than the wild type, suggesting that wild-type levels of phosphatidylcholine are required for full competitivity of Bradyrhizobium in symbiosis with peanut plants.
authors.affiliation: Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, Córdoba, Argentina.
authors.forename: Daniela B
authors.initials: DB
authors.lastname: Medeot
authors.forename: Christian
authors.initials: C
authors.lastname: Sohlenkamp
authors.forename: Marta S
authors.initials: MS
authors.lastname: Dardanelli
authors.forename: Otto
authors.initials: O
authors.lastname: Geiger
authors.forename: Mirta García
authors.initials: MG
authors.lastname: de Lema
authors.forename: Isabel M
authors.initials: IM
authors.lastname: López-Lara
mesh_terms: D010367:Arachis / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D020369:Bradyrhizobium / Q000737:chemistry / Q000166:cytology* / Q000302:isolation & purification / Q000502:physiology*; D004269:DNA, Bacterial / Q000235:genetics; D018628:Gene Dosage; D055786:Gene Knockout Techniques; D008124:Locomotion; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000032:analysis*; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D010713:Phosphatidylcholines; D008780:Methyltransferases; C435200:PmtA protein, bacteria; D017855:Transferases (Other Substituted Phosphate Groups); C483298:CDP-diacylglycerol choline O-phosphatidyltransferase