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Seven strains of root nodule bacteria (PF1, PF2, PF12, PF16, PF21, PF25, PF40) were isolated from root nodules of tree legume Paraserianthes falcataria at West Java and North Sumatra, Indonesia. One strain isolated from nodule of Glycine max growing Central Java (Bj31) was confirmed to be able to nodulate to P. falcataria. In this report, several biological characters of total 8 strains to be nodulate on P. falcataria were investigated concerning with (Brady)Rhizobium group as follows; i) cell size, ii) generation time, iii) growth pH, iv) IAA production, v) several enzyme activities, and vi) nodulation and nitrogen fixation abilities. All strains were confirmed the nodulation and nitrogen fixation to P. falcataria seedlings. From the results of generation time measurement, the strains are classified into two groups, strains PF1, PF12 and PF40 are belonging to fast growing type, and other 5 strains, PF2, PF16, PF21, PF25 and Bj31 are slow growing type. The strains, except the strains PF2 and PF16 were able to grow in acidic media condition (≦ pH 4.5). Strains PF2, PF16, PF21 and PF25 exhibited long cell size (2.4~3.7 μm). The particular production of IAA could not be detected from the tested strains. Strain PF12 was distinguished with other strains with melanin production. Furthermore, these strains were examined as genetic diversity by RAPD electrophoretogram pattern analysis and 16S rRNA partial sequence analysis to compare with other α Proteobacteria. From 16S rRNA sequencing, strains PF1 and PF40 were closely related to Rhizobium tropici, and strains PF2, PF16, PF25 and Bj31 were identified to close to Bradyrhizobium japonicum group and strain PF21 was grouped with Blastobacter denitrificans. However, strain PF12 was not fit in α Proteobacteria by 16S rRNA sequence analysis. Strain PF12 exhibited more than 90% similarity with clinical strain Burkholderia cepacia, in β Proteobacteria by 16S rRNA sequencing analysis. These results show the 7 strains isolated from P. falcataria nodules, which are able to nodulate and fix nitrogen in their host plant, were arranged 4 different positions on the phylogenetic tree composed by partial sequence of 16S rRNA. It is presumed that nod- and nif- genes of (Brady)Rhizobium might transmit horizontally to other bacterial cells in rhizosphere and become to nodulate to Paraserianthes falcataria roots. |
