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Noisangiam R.,Suranaree University of Technology | Nuntagij A.,Soil Microbiology Research Group | Pongsilp N.,Silpakorn University | Boonkerd N.,Suranaree University of Technology | And 3 more authors.
Systematic and Applied Microbiology | Year: 2010

Bacterial strains from inoculated soybean field soil in Thailand were directly isolated using Bradyrhizobium japonicum selective medium (BJSM), on the basis of Zn2+ and Co2+ resistance of B. japonicum and B. elkanii. The isolates were classified into symbiotic and non-symbiotic groups by inoculation assays and Southern hybridization of nod and nif genes. In this study, a nearly full-length 16S rRNA gene sequence showed that the non-symbiotic isolates were more closely related to members of Rhodopseudomonas and to a number of uncultured bacterial clones than to members of Bradyrhizobium. Therefore, a polyphasic study was performed to determine the taxonomic positions of four representatives of the non-symbiotic isolates. Multilocus phylogenetic analysis of individual genes and a combination of the 16S rRNA and three housekeeping genes (atpD, recA and glnII) supported the placement of the non-symbiotic isolates in a different genus. The ability of heavy metal resistance in conjunction with phenotypic analyses, including cellular fatty acid content and biochemical characteristics, showed that the non-symbiotic isolates were differentiated from the other related genera in the family Bradyrhizobiaceae. Therefore, the non-symbiotic isolates represented a novel genus and species, for which the name Metalliresistens boonkerdii gen. nov., sp. nov. is proposed. The type strain is NS23 (= NBRC 106595T=BCC 40155T). © 2010 Elsevier GmbH.

Pongsilp N.,Silpakorn University | Leelahawonge C.,Silpakorn University | Nuntagij A.,Soil Microbiology Research Group | Teaumroong N.,Suranaree University of Technology | Boonkerd N.,Suranaree University of Technology
African Journal of Microbiology Research | Year: 2010

We identified 12 strains of root-nodule bacteria isolated from Pueraria mirifica, an indigenous Thai medicinal legume, grown naturally in Thailand. Sequence analysis of the 16S rRNA gene indicated that 9 and 3 strains belonged to the genera Rhizobium and Bradyrhizobium, respectively, with high identity (96 - 100%). All 9 P. mirifica-nodulating Rhizobium strains were placed in Rhizobium spp. clade of the constructed phylogenetic tree. While, the closest phylogenetic neighbours of P. mirifica-nodulating Bradyrhizobium were Bradyrhizobium liaoningense, Bradyrhizobium yuanmingense and Bradyrhizobium japonicum. The strains were characterized by phenotypic characteristics including utilization of carbon and nitrogen sources, resistance to antibiotics, requirement for vitamins and enzymatic patterns. Both genera that nodulated P. mirifica were phenotypically indistinguishable. Growth tests at different conditions revealed that the strains, even among the same genus, varied in their response to the levels of temperature, pH and NaCl. Rhizobium DASA 64006 was the only one strain that could propagate at all desired conditions. © 2010 Academic Journals.

Habibi S.,Tokyo University of Agriculture and Technology | Djedidi S.,Tokyo University of Agriculture and Technology | Prongjunthuek K.,Soil Microbiology Research Group | Mortuza M.F.,Bangladesh Atomic Energy Commission | And 3 more authors.
Plant and Soil | Year: 2014

Aims: We aimed to identify plant growth-promoting rhizobacteria that could be used to develop a biofertilizer for rice. Methods: To obtain plant growth-promoting rhizobacteria, rhizosphere soils from different crops (rice, wheat, oats, crabgrass, maize, ryegrass, and sweet potato) were inoculated to rice plants. In total, 166 different bacteria were isolated and their plant growth-promoting traits were evaluated in terms of colony morphology, indole-3-acetic acid production, acetylene reduction activity, and phosphate solubilization activity. Moreover, genetic analysis was carried out to evaluate their phylogenetic relationships based on 16S rRNA sequence data. Results: Strains of Bacillus altitudinis, Pseudomonas monteilii, and Pseudomonas mandelii formed associations with rice plants and fixed nitrogen. A strain of Rhizobium daejeonense showed nitrogen fixation activity in an in vitro assay and in vivo. Strains of B. altitudinis and R. daejeonense derived from rice rhizosphere soil, strains of P. monteilii and Enterobacter cloacae derived from wheat rhizosphere soil, and a strain of Bacillus pumilus derived from maize rhizosphere soil significantly promoted rice plant growth. Conclusions: These methods are effective to identify candidate species that could be developed as biofertilizers for target crops. © 2014 Springer International Publishing Switzerland.

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