Isolation of free-living nitrogen-fixing bacteria from the rhizosphere of rice.

Abstract

Bacterial flora of rhizosphere of the rice plant was examined to determine the relationship of nitrogen-fixing bacteria to rice plants. Of 7,344 bacterial strains from the rhizosphere, 1,005 strains (13.7%) reduced acetylene. Representative 74 strains with acetylene reduction activity were selected for identification. All of these strains were gram negative, aerobic or facultatively anaerobic, and most had ubiquinone (Q-10) and cellular fatty acid composition, mainly with straight-chain fatty acids. Twenty-two strains were assigned to the following known species: Azospirillum brasilense Tarrand, Krieg and Dobereiner (1 strain), Azospirillum lipoferum Tarrand, Krieg and Dobereiner (1 strain), Enterobacter cloacae (Jordon) Hormaeche and Edwards (4 strains), Erwinia herbicola (Lohnis) Dye (2 strains), Klebsiella oxytoca (Flugge) Lautrop (6 strains), and Xanthobacter autotrophicus (Baumgarten, Reh and Schlegel) Wiegel, Wilke, Baumgarten, Opitz and Schlegel (8 strains). Fifty-two strains could not be assigned to any known species.Since YOSHIDA and ANCAJAS (1) reported the association of free-living nitrogen-fixing bacteria with rice plants, several workers have isolated such bacteria and investigated the interrelation between bacteria and rice (2-17). Until recently, Azospirillum lipoferum (11-14), Azospirillium brasilense (12-14), Enterobacter cloacae (12,13,15), Klebsiella oxytoca (12, 13), Pseudomonas paucimobilis (12, 13), Pseudomonas sp. (16,17), and Clostridium sp. (5) have been isolated. SANO et al. (18) reported a seasonal variation of nitrogen-fixation in the rice plant and a possible symbiotic relation between bacteria and the plants. We have collaborated with them to investigate the relation between the nitrogen-fixing bacteria and the rice plant. This paper deals with the characterization and identification of the free-living nitrogen-fixing bacteria isolated from rice roots and paddy soil.

Sphingomonas azotifigens sp. nov., a nitrogen-fixing bacterium isolated from the roots of Oryza sativa

“…Oyaizu- Masuchi & Komagata (1988) reported the isolation of a number of free-living, nitrogen-fixing bacteria from the rhizosphere or roots of rice plants. These isolates were classified into ten groups on the basis of phenotypic and chemotaxonomic characteristics.…”

Comparison of Nitrogen-fixing Bacterial Flora of Rice Rhizosphere in the Fields Treated Long-term with Agrochemicals and Non-agrochemicals

“…Oyaizu-masuchi and Komagata 22) examined nitrogen-fixing bacteria from the roots of rice grown in Mishima City, Shizuoka prefecture, and were only able to identify 22 isolates from a total of 74 isolates. In our study, Polaromonas vacuolata, Mycobacterium obuense and Microbacterium oxydans were the first isolates as nitrogen-fixing bacteria.…”

“…Azospirillum, a common root-inhabiting nitrogenfixing bacterium, is often isolated from the rice rhizospheres of paddy fields 19,20,21) . Azospirilla have been isolated from paddy fields in Shizuoka 22) and Aichi Prefecture 23) which are both near the fields used in the present study. Proteobacteria including Azospirilla were not isolated in the present study.…”

Parasutterella secunda sp. nov., isolated from human faeces and proposal of Sutterellaceae fam. nov. in the order Burkholderiales

“…The typical fragmentation of a ubiquinone ring nucleus at mole peak m/z 197 was not detected in all these strains, indicating ubiquinones are not present in strains of the genera Parasutterella and Sutterella. Contrary to this, species of the family Alcaligenaceae have, in general, been characterized by the presence of ubiquinone-8 (Q-8) as the major isoprenoid quinone (Table 1; Fletcher et al, 1987;Oyaizu-Masuchi & Komagata, 1988).A 1485 bp region of the 16S rRNA gene of strain YIT 12071 T was sequenced. Database searches revealed a high similarity between strain YIT 12071 T and P. excrementihominis (90.0 %).…”