Phosphatidylcholine levels of peanut-nodulating Bradyrhizobium sp. SEMIA 6144 affect cell size and motility.
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.
Medeot
Daniela B
DB
Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, Córdoba, Argentina.
Sohlenkamp
Christian
C
Dardanelli
Marta S
MS
Geiger
Otto
O
de Lema
Mirta García
MG
López-Lara
Isabel M
IM
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
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