Nodulation of Sesbania species by Rhizobium (Agrobacterium) strain IRBG74 and other rhizobia.
Concatenated sequence analysis with 16S rRNA, rpoB and fusA genes identified a bacterial strain (IRBG74) isolated from root nodules of the aquatic legume Sesbania cannabina as a close relative of the plant pathogen Rhizobium radiobacter (syn. Agrobacterium tumefaciens). However, DNA:DNA hybridization with R. radiobacter, R. rubi, R. vitis and R. huautlense gave only 44%, 5%, 8% and 8% similarity respectively, suggesting that IRBG74 is potentially a new species. Additionally, it contained no vir genes and lacked tumour-forming ability, but harboured a sym-plasmid containing nifH and nodA genes similar to those in other Sesbania symbionts. Indeed, IRBG74 effectively nodulated S. cannabina and seven other Sesbania spp. that nodulate with Ensifer (Sinorhizobium)/Rhizobium strains with similar nodA genes to IRBG74, but not species that nodulate with Azorhizobium or Mesorhizobium. Light and electron microscopy revealed that IRBG74 infected Sesbania spp. via lateral root junctions under flooded conditions, but via root hairs under non-flooded conditions. Thus, IRBG74 is the first confirmed legume-nodulating symbiont from the Rhizobium (Agrobacterium) clade. Cross-inoculation studies with various Sesbania symbionts showed that S. cannabina could form fully effective symbioses with strains in the genera Rhizobium and Ensifer, only ineffective ones with Azorhizobium strains, and either partially effective (Mesorhizobium huakii) or ineffective (Mesorhizobium plurifarium) symbioses with Mesorhizobium. These data are discussed in terms of the molecular phylogeny of Sesbania and its symbionts.
Cummings
Stephen P
SP
School of Applied Sciences, Ellison Building, University of Northumbria, Newcastle-upon-Tyne, UK.
Gyaneshwar
Prasad
P
Vinuesa
Pablo
P
Farruggia
Frank T
FT
Andrews
Mitchell
M
Humphry
David
D
Elliott
Geoffrey N
GN
Nelson
Andrew
A
Orr
Caroline
C
Pettitt
Deborah
D
Shah
Gopit R
GR
Santos
Scott R
SR
Krishnan
Hari B
HB
Odee
David
D
Moreira
Fatima M S
FM
Sprent
Janet I
JI
Young
J Peter W
JP
James
Euan K
EK
D000217:Acyltransferases / Q000032:analysis / Q000235:genetics; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D009586:Nitrogen Fixation; D010088:Oxidoreductases / Q000032:analysis / Q000235:genetics; D020653:Peptide Elongation Factor G / Q000032:analysis / Q000235:genetics; D010802:Phylogeny; D010957:Plasmids / Q000032:analysis / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D012231:Rhizobium / Q000235:genetics* / Q000648:ultrastructure; D053204:Root Nodules, Plant / Q000382:microbiology* / Q000648:ultrastructure; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D049931:Sesbania / Q000382:microbiology* / Q000648:ultrastructure; D013045:Species Specificity; D013559:Symbiosis
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D020653:Peptide Elongation Factor G; D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase; D000217:Acyltransferases; C060770:NodA protein, Rhizobiales