Competition by beta-rhizobia Burkholderia and Cupriavidus for nodulation of Mimosa spp.

• Main Authors: Jui-Hsing Chou, 周瑞興
• Other Authors: Chiu-Chung Young
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/59863278691896833075

博士 === 國立中興大學 === 土壤環境科學系所 === 97 === Three groups of strains were isolated from nitrogen-fixing root nodules of M. pigra, M. scabrella, M. bimucronata, M. caesalpiniifolia from Taiwan, Venezuela and Brazil. On the basis of 16S rDNA sequence similarities, all the strains were shown previously to belong to the genus Burkholderia. A polyphasic approach, including 16S rDNA phylogenetic tree, extensive biochemical characterization, fatty acid methyl ester analysis, and DNA-DNA hybridizations, was used to clarify the taxonomic position of these strains further; the three groups of strains are here classified within a novel species, for which the name Burk. mimosarum PAS44T, Burk. nodosa Br3437T, and Burk. sabiae Br3407T is proposed. The b-rhizobial strains Cupriavidus taiwanensis 184, Burkholderia mimosarum PAS44 and Burk. phymatun STM815 were originally isolated from root nodules of Mimosa spp. and Machaerium lunatum in Taiwan and French Guiana. C. taiwanensis 184, Burk. mimosarum PAS44 and Burk. phymatun STM815 formed effective symbioses with the common invasive species Mimosa pudica, M. diplotricha, and M. pigra. In order to competition studies were performed three of the β-rhizobial symbionts for nodulation of these invasive Mimosa species. C. taiwanensis 184 and Burk. phymatun STM815 conjugated with the gfp gene and Burk. mimosarum PAS44 conjugated with the gus gene were co-inoculated into the three Mimosa spp. plant. Under the hydroponic condition, results were showed different host-affinity that inoculant different ratio of three strains. Especially Burk. mimosarum PAS44 showed complete dominance in nodule occupation compared to C. taiwanensis 184, and it occupied almost all the nodules on M. pudica, M. diplotricha and M. pigra, even with a negative inoculation ratio of 1:10000, Burk. mimosarum PAS44 still occupied 92.2% nodules. However, under soil conditions, although Burk. mimosarum PAS44 still showed dominance in occupation of M. pigra nodules over C. taiwanensis 184. It only showed partially dominance in occupation of M. pudica and M. diplotricha nodules. Results were not due to initial inoculum ratio, rates of bacterial growth, rhizobia-rhizobia growth inhibition or individual nodulation rate. Under Mimosa spp. (M. pigra and M. pudica) adsorption rate, Burk. mimosarum PAS44 showed adsorption up to one hundred times quicker than C. taiwanensis under root in liquid nutrient culture. In motility test, C. taiwanensis 184 showed moving very slowly, but Burk. mimosarum PAS44 showed moving quickly and straight, motility speed of Burk. mimosarum PAS44 about ten times higher than the C. taiwanensis 184. Burk. mimosarum PAS44 was also able to utilize more than twelve carbon and energy sources. According with adsorption rate, motility, and carbon utilization thus indicate that Burk. mimosarum PAS44 is more competitive than C. taiwanensis 184 at nodulating Mimosa spp., especially under root in liquid nutrient culture. The largest significant effect was for M. pudica, in which C. taiwanensis 184 formed 59.1% and 83.3% of the nodules in the presence of 0.5 mM KNO3　and 1.25 mM (NH4)2SO4 in liquid nutrient culture, but symbiosis root nodules became lesser. Environmental N concentration is therefore suggested as a factor in the competitive success of the b-rhizobial symbiosis.