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.

Bacterial populations in juvenile maize rhizospheres originate from both seed and soil

“…Conversely, EMBRAPA rhizospheres may have acquired their OTU 212 from soils as only 0.4 % of the conseq in sterile sand rhizospheres belonged to that OTU, compared to 35 and 39 % for rhizospheres from subsoil and terra preta grown plants. The apparent dominance of Burkholderia species that we have observed in juvenile maize plants is not unprecedented: Burkholderia have been reported to be the most abundant genera of bacteria in rhizospheres of turf grasses (Vandenkoornhuyse et al 2007), in rhizospheres of maize grown under field conditions (Bouffaud et al 2012;Peiffer et al 2013), in hybrid maize seeds in China (Liu et al 2013b), in moss sporophytes and gametophytes (Bragina et al 2013) and in mimosa roots (Elliott et al 2009). More than one species of Burkholderia matches OTU 212, highlighting a general problem with relying only on 16S data to predict specific taxonomy, ecology or behaviour of bacteria.…”

Purification and Biochemical Characterization of a Novel Ecto-Apyrase, MP67, from Mimosa pudica

“…This is probably because we used cDNAs prepared from leaves. However, a legume-specific type of apyrase might exist in Mimosa, because symbiosis of Rhizobium and M. pudica has been reported (Elliott et al, 2009), and the apyrase might contribute to the symbiosis. We will attempt to isolate a legume-specific apyrase from Mimosa roots in future work.…”

Molecular mechanisms underlying the close association between soil Burkholderia and fungi

“…Burkholderia are particularly abundant in soil where they can be associated with a wide range of plants (Elliott et al, 2009;Carlier and Eberl, 2012), invertebrates (Kikuchi et al, 2005) and fungi (Warmink et al, 2009;Uroz et al, 2012;Scherlach et al, 2013). Since Burkholderia are mostly found in acidic soils (Stopnisek et al, 2014), interactions with fungi might be of particular relevance as fungi also favour acidic environments.…”