• Korean Journal of Soil Science and Fertilizer
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• v.20 no.2
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• pp.185-192
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• 1987

A green house experiment was conducted to find out the acetylene reducing and $N_2$-fixing activity from photosynthetic and aerobic heterotrophic nitrogen fixing microorganisms in submerged paddy soil under different agricultural locality, soil series, soil texture, soil type, and drainage condition in which samples taken from without nitrogen treatment plot of NPK trials on 16 sites of the farmer's field. The results obtained were summarized as follows: 1. The highest acetylene reducing activity was observed at 7 days after incubation in the light condition (photo synthetic microbes+heterotrophic bacteria) while it was observed at 35 days incubation in the dark condition (heterotrophic bacteria). 2. Among the soil series, photosynthetic nitrogen fixing activity was pronounced more in Jangae, Ogcheon and Hwadong series while lower was obtained in Buyong and Daejeong series. Aerobic heterotrophic nitrogen fixing activity was high in Buyong and Daejong series. 3. Estimated amount of $N_2$-fixation from acetylene reducing activity was equivalented to 3.0 mg in light condition and 4.9 mg/100g/105 days in dark condition. 4. Among the agricultural locality, photosynthetic nitrogen fixing activity was high in rather warm southern part while heterotrophic nitrogen fixing activity was predominated more in mountainous area and Chungcheong continental. 5. Photosynthetic nitrogen fixing activity was predominated in high productive soil while aerobic heterotrophic nitrogen fixing activity was pronounced more in crose coarse sandy soil. 6. The soils properties of high photosynthetic nitrogen fixing activity were constituted of poorly or imperfectly drained clay or clay loam soil while heterotrophic nitrogen fixing activity was pronounced more in well to moderately well drained sandy or sandy loam soil.

• Korean Journal of Microbiology
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• v.25 no.2
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• pp.129-136
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• 1987

Nitrogen fixing activity associated with 40 varieties of rice was assayed at heading stage by an in situ acetylene reduction method. The in situ acetylene reduction activity and population of nitrogen fixing bacteria obtained on nitrogen-free malate medium for Azospirillum spp. enrichment showed positive correlation. Six Azospirillum spp. with high nitrogenase activity were isolated from the rice roots, from which five spp. were identified as A. lipoferum and one was A. brasilense. The physiological characteristics of the six Azospirillum isolates, that is, carbon source utilization, biotin requirement, antibiotic resistance, indole acetic acid excretion, plasmid profile and protein patterns were compared.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.17-29
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• 2016

Though there is an abundant supply of nitrogen in the atmosphere, it cannot be used directly by the biological systems since it has to be combined with the element hydrogen before their incorporation. This process of nitrogen fixation ($N_2$-fixation) may be accomplished either chemically or biologically. Between the two elements, biological nitrogen fixation (BNF) is a microbiological process that converts atmospheric di-nitrogen ($N_2$) into plant-usable form. In this review, the genetics and mechanism of nitrogen fixation including genes responsible for it, their types and role in BNF are discussed in detail. Nitrogen fixation in the different agricultural systems using different methods is discussed to understand the actual rather than the potential $N_2$-fixation procedure. The mechanism by which the diazotrophic bacteria improve plant growth apart from nitrogen fixation such as inhibition of plant ethylene synthesis, improvement of nutrient uptake, stress tolerance enhancement, solubilization of inorganic phosphate and mineralization of organic phosphate is also discussed. Role of diazotrophic bacteria in the enhancement of nitrogen fixation is also dealt with suitable examples. This mini review attempts to address the importance of diazotrophic bacteria in nitrogen fixation and plant growth improvement.

• Current Research on Agriculture and Life Sciences
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• v.5
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• pp.40-51
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• 1987

This experiment was conducted to search for Rhizobia with good nitrogen fixation abilities and to investigate their physiological characteristics isolated from 12 soybean cultivars and the affinities of root nodule bacteria with soybeans. The results obtained were as follows; Based on colors, Rhizobia grown on YMA medium were divided into 3 groups, i. e., white, translucent and transparent, amounting to 60, 30 and 10%, respectively. In litmus milk reaction, the strains which produced alkali, acid serum, alkaline serum and acid reached to 51, 29, 9 and 11%, respectively. Strains, S022, and S096 were slow-growers and produced alkaili, while strains, S080, S-090, and S118 were fastgrowers and produced acid. The growth of root nodule bacteria on YMA medium was favorable between the initial pHs of 6.0~7.0. Glutamine, asparagine and al1antoin as nitrogen sources enhanced the growth of root nodule bacteria. All the strains tested formed nodules on the soybean roots, and the strains with good symbiotic nitrogen fixation abilities that had white color, small colony, nitrate reduction abilities and no nitrite reduction abilities showed comparatively high nitrogen fixing activities. Some strains varied in nitrogen fixing activities according to soybean cultivars, and a few strains fanned ineffective nodules which showed no nitrogen fixing activity.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.2
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• pp.193-197
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• 1987

Associative heterotrophic nitrogen fixing bacteria were identified by immunodiffusion method in the histosphere of Planta-ginaceae, Caryophllaceae, Gramineae, and two types of rice cultivars. Twenty four strains associative heterotrophic bacteria with high ARA (more than 10nmole/tube/hr) were isolated from the histosphere of grasses and rice.* Those strains were related with 8 species of Azospirillum, 11 species of Pseudomonas, 2 species of Klebsiella and 2 species of Agrobacterium. Among them Azospirillum sp. and Pseudomonas sp. were predominant in histosphere of grasses and rice cultivars. From the histosphere of Oryza sativa, and Sagina maxima, the strains of Azospirillum, Pseudomonas, Klebsiella, and Agrobacter were identified while Pseudomonas was identified from Ischaemum anthephoroides, Plantago lanceolata, Miscanthus sacchuriflorum, and only Azospirillum was identified from Zoisia sinica, respectively. Associative nitrogen fixing heterotrophic bacteria were more abundant in the histosphere of Oryza sativa and Sagina maxima than that of other grasses grown in saline and reclaimed saline paddy soil.

• Korean Journal of Microbiology
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• v.29 no.2
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• pp.130-135
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• 1991

The effects of a herbicide butachlor[2-chloro-2', 6'-diethyl-N-(butoxymethyl) acetanilide] on the growth of the purple non-sulfur bacteria were investigated. The butachlor inhibited the growth of all species tested by 18-51%, except Rhodospirillum rubrum at concentrations of M, which would be field capacity. The photosynthetic growth rate of the species in the presence of butachlor was influenced by the nitrogen source. Cultures supplied with (NH&S04 showed a somewhat higher growth rate than those fixing dinitrogen, but they were more susceptible to butachlor (26-51%). On the contrary, butachlor enhanced the growth rate of Rhodospirillum rubrum in nitrogen gas conditions. When the culture was performed in medium with butachlor as the carbon source, the cells of fixing dinitrogen showed a higher exhaustion of butachlor than those supplemented with (N&)2S04, which exhaustion was examined by a decrease of the major absorbance at 213 nm and 260 nm. The exhaustion of butachlor as the carbon source had relation with the growth of the cells. The alkalization of culture supplemented with nitrogen gas was found in the cells treated with butachlor or untreated. The butachlor affected the carotenoid region but bacteriochlorophyll remained unaffected.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.1
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• pp.69-76
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• 1987

The aerobic heterotrophic bacteria in the histosphere associated with grasses (Gramineae, Caryphyllaceae, Crucifereae) and rice cultivars in saline and reclaimed saline paddy soils were varied with species and rice cultivars. The fraction of aerobic heterotrophic $N_2$-fixing bacteria to the total aerobic heterotrophic bacteria were averaged to eighteen percent in the histosphere of grasses and rice. Acetylene reducing activity of these bacteria were ranged from 1 to 24 n mole/tube/hr. Most of the bacteria strains were predominated of hydrogen utilizing bacteria. The majority of these bacteria were closed to Pseudomonas, Azospirillum, Klebsiella and Agrobacter.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.48-55
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• 2004

Six strains of an obligate predatory bdellovibrio isolate that preys on Burkholderia glumae in rice paddy field water and rhizosphere soil, were identified and characterized. The numbers of Bdellovibrio cells varied from $3.2{\times}10^3$ to $9.2{\times}10^3$ plaque-forming unit/g after enrichment in cells of B. glumae. Prey range tests with six Bdellovibrio strains and 17 prey strains of rice-pathogenic, antibiosis-related, or nitrogen-fixing bacteria resulted in unique predation patterns in related prey cells. Strain BG282 had the widest prey range on 7 plant pathogenic bacteria among the 17 prey strains tested. However, no predation occurred with strains of Azospirillum brasilense, Paenibacillus polymyxa, Pseudomonas fluorescens, P. putida, and Serratia marcescens that are associated with antibiosis or nitrogen fixation in the rice ecosystem. Identification was confirmed by the presence of typical bdelloplast in the prey cells of B. glumae and by a PCR assay using B. bacteriovorus-specific primers. Furthermore, 16S rDNA sequencing of the six bdellovibrio strains showed a homology range of 97.2% to 99.2% to the type strain of B. bacteriovorus.

• Journal of Korean Society of Forest Science
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• v.77 no.2
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• pp.229-234
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• 1988

To evaluate potential of VA mycorrhizal fungi for promoting growth of nitrogen-fixing trees and efficiency of fungal inoculation in relation to soil fertility and dual inoculation with bacteria, Alnus firma was grown for six months in pots with steam-sterilized soil after inoculation with Glomus mosseae, and Robinia pseudoacacia was grown in the fumigated field after inoculation with native Glomus sp. and Gigaspora sp. In unfertilized Alnus plants, 27% increase in dry weight(or 18% in height) was observed by Glomus inoculation, while plants inoculated with both VA mycorrhiza and actinomycete(crushed nodule inoculum) showed synergistic effect of 83% dry weight increase over uninoculated plants. In fertilized Alnus plants, mycorrhizal inoculation alone or dual inoculation with actinomycete resulted in depression of height and dry weight of plants. In case of Robinia, dual inoculation stimulated height growth by 23% (or dry weight by 25%) over the control in unfertilized field, while 13% more height growth(or 21% more dry weight) was observed in fertilized field. It is concluded that VA mycorrhizae, especially Glomus mosseae, have a potential for growth enhancement in Alnus, that synergistic effect of dual inoculation(mycorrhiza + actinomycete) exists in both Alnus and Robinia, and that responses of these plants to VA mycorrhiza are more pronounced in unfertilized soil.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.3
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• pp.269-274
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• 1987

A laboratory experiment was conducted to find out the effect of inoculation with plant growth of associative $N_2$-fixing bacteria on the combination of eight different rice seedling with seven different associative $N_2$-fixing bacteria in which were isolated and identified from grasses and rice in saline and reclaimed saline paddy soil. Those were examined in N-free axenic culture medium. The result of this experiment exemplified the contribution of associative $N_2$-fixing bacteria to their host plant were varied much by the combination of rice cultivars and bacterial strains. Acetylene reduction ($N_2$-fixation) activity seems to be more variable with respect to the combination of rice cultivars and bacterial strains. The relationship between acetylene reduction activity and rice performance such as dry matter weight, plant height, root length, and number of root were statistically insignificant. However, in comparision with the control, the dry matter yield of Annapuruna was increased by inoculation of all the seven bacteria strains. Among the seven rice cultivars, the average acetylene reducing activity was the highest in Annapuruna, and Shingwang, and the lowest in IR-8 inoculated with Pseudomonas sp H8. Among the seven bacterial strains the highest acetylene reducing activity was obtained by the combination of Shingwang with Pseudomonas sp H8.