title: Burkholderia spp. are the most competitive symbionts of Mimosa, particularly under N-limited conditions.
abstract: Bacteria isolated from Mimosa nodules in Taiwan, Papua New Guinea, Mexico and Puerto Rico were identified as belonging to either the alpha- or beta-proteobacteria. The beta-proteobacterial Burkholderia and Cupriavidus strains formed effective symbioses with the common invasive species Mimosa diplotricha, M. pigra and M. pudica, but the alpha-proteobacterial Rhizobium etli and R. tropici strains produced a range of symbiotic phenotypes from no nodulation through ineffective to effective nodulation, depending on Mimosa species. Competition studies were performed between three of the alpha-proteobacteria (R. etli TJ167, R. tropici NGR181 and UPRM8021) and two of the beta-rhizobial symbionts (Burkholderia mimosarum PAS44 and Cupriavidus taiwanensis LMG19424) for nodulation of these invasive Mimosa species. Under flooded conditions, B. mimosarum PAS44 out-competed LMG19424 and all three alpha-proteobacteria to the point of exclusion. This advantage was not explained by initial inoculum levels, rates of bacterial growth, rhizobia-rhizobia growth inhibition or individual nodulation rate. However, the competitive domination of PAS44 over LMG19424 was reduced in the presence of nitrate for all three plant hosts. The largest significant effect was for M. pudica, in which LMG19424 formed 57% of the nodules in the presence of 0.5 mM potassium nitrate. In this host, ammonium also had a similar, but lesser, effect. Comparable results were also found using an N-containing soil mixture, and environmental N levels are therefore suggested as a factor in the competitive success of the bacterial symbiont in vivo.
authors.affiliation: College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. g.elliott@macaulay.ac.uk
authors.forename: Geoffrey N
authors.initials: GN
authors.lastname: Elliott
authors.forename: Jui-Hsing
authors.initials: JH
authors.lastname: Chou
authors.forename: Wen-Ming
authors.initials: WM
authors.lastname: Chen
authors.forename: Guido V
authors.initials: GV
authors.lastname: Bloemberg
authors.forename: Cyril
authors.initials: C
authors.lastname: Bontemps
authors.forename: Esperanza
authors.initials: E
authors.lastname: Martínez-Romero
authors.forename: Encarna
authors.initials: E
authors.lastname: Velázquez
authors.forename: J Peter W
authors.initials: JP
authors.lastname: Young
authors.forename: Janet I
authors.initials: JI
authors.lastname: Sprent
authors.forename: Euan K
authors.initials: EK
authors.lastname: James
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology*; D020562:Betaproteobacteria / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020459:Genes, rRNA; D008800:Mexico; D031298:Mimosa / Q000382:microbiology*; D009584:Nitrogen / Q000378:metabolism*; D010219:Papua New Guinea; D010802:Phylogeny; D011647:Puerto Rico; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013559:Symbiosis; D013624:Taiwan
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D009584:Nitrogen