Strains Of Nitrogen-fixing Bacteria Research Articles

Солтүстік Қазақстан аймағының әртүрлі топырақ типтеріндегіазот бекітуші микроағзалардың таралуы

The use of biopreparations based on soil microorganisms to improve soil fertility, crop productivity and reduce the spread of fungal diseases of grain crops is one of the promising and environmentally friendly directions. This, in turn, requires comprehensive work on the creation, evaluation and introduction of highly effective Kazakhstani biological preparations. The article presents data on the distribution of nitrogen-fixing bacteria and actinomycetes on different types of soils in Northern Kazakhstan, identified by sowing soil suspensions by serial dilutions. More than 100 new strains of nitrogen-fixing bacteria and actinomycetes were isolated on solid selective nutrient media. In order to create a biofertiliser, the pathogenicity and growth intensity of new nitrogen-fixing bacteria and actinomycetes were studied, and their cultural and morphological characteristics were described. The 30 most active strains such as №21S, №19S, №31S, №91S, №3S, №56S, №51S, №62S, №55S, №70S, №53S, №20S, №2S, №81S, №7S, №54S, №57S, №35S, №84S, №22S, №9S, №12S, №8S, №10S, №69S, №52S, №49S, №11S, №6S, №59S, which will be used to make biologics. In the future, these strains will be studied for their growth-stimulating, fungicidal properties, etc., and will also be used in the development of microbiological technology for the production of biological preparations based on nitrogen-fixing and actinomycetes capable of increasing productivity.

Study on Diversity of Culturable Bacteria in Maize Field Soil under Pesticide Stress

The effects of pesticide application on the diversity of culturable bacteria in the soil of corn farmland in Sanjiang Plain were studied, and the bacteria capable of degrading acetochloramine in the soil samples were screened. In the black soil of corn farmland where “ethyldiazine 86” was applied, the experimental group and the control group were set, and the culturable bacteria in the soil samples of the two groups were cultured and screened by coating plate method. The 16S rRNA gene sequences and morphological characteristics were analyzed to determine the species of bacteria. Selective medium was designed to screen pesticide degrading bacteria. 19481 strains of culturable bacteria were cultured in the experiment, including 7854 strains in the experimental group and 11627 strains in the control group. A total of 65 strains were screened, purified and preserved, including 16 strains of phosphorus solubilizing bacteria, 9 strains of nitrogen fixing bacteria and 4 strains of pesticide degrading bacteria. The community structure of soil bacteria was mainly composed of Pseudomonas, Pantoea and Bacillus, and the dominant bacterium was Pseudomonas. The four pesticide-degrading bacteria were all Pseudomonas migulae. Long-term application of pesticides can reduce the number of culturable-bacteria in the soil, and the bacteria richness is also decreased. This study provides a theoretical basis for understanding the bacterial diversity of pesticide residue soil, protection and sustainable utilization of black soil.

Effect of nitrogen-fixing bacteria on resource investment of the root system in an invasive clonal plant under low nutritional environment

Nitrogen-fixing bacteria (NFB) converts nitrogen from the air into a nitrogen source to support plants' requirements. However, the importance of NFB for invasive plants under nitrogen (N) limitation is not well understood. In this study, we investigated the response of Solidago canadensis, an invasive clonal plant, to low nitrogen conditions with the colonization of two NFB strains, using a completely sterile culture system. We found that under very low nitrogen, the addition of both NFB strains significantly increased the investment of belowground biomass and total biomass, and greatly promoted the development of the root system (p < 0.05). Importantly, the significant decrease of anthocyanin and significant increase in root volume and root average diameter indicated that NFB reduced nutritional stress and promoted roots under extreme nitrogen deficiency. Our findings suggest that the interaction with NFB may contribute to the invasiveness of S. canadensis through investing more resources into the root system in a resource-poor environment.

Dynamics of alfalfa leaf area depending on nitrogen feeding type

The results of field studies for 2017-2019 of dynamics of assimilation surface of alfalfa crops depending on the type of nitrogen nutrition and symbiotic activity of crops are given. Tests with Medicago varia Mart. were carried out in environmental conditions of the pre-mountain zone of RNO-Alania (540 meters above sea level) on the black earth leached with close occurrence of pebbles. Mineral and symbiotrophic types of nitrogen nutrition of alfalfa plants were compared. The experience scheme included options: control - natural soil fertility; In-1800 - treatment of seeds with inoculum of strains of nitrogen-fixing bacteria selected in high mountain conditions (1800 m above sea level); Strain 425a - inoculation of seeds with industrial strain rhizotorphin (strain 425a); N30 - starting nitrogen dose; N30+In is the joint use of highland strains of bacteria and starting doses of nitrogen. Seeds were treated with the strains studied before sowing. Mineral nitrogen fertilizers were introduced annually early in spring in the form of starting doses. It has been established that the minimum areas of leaves on all variants are observed in the first year of life, in the second year of use of crops the maximum assimilation surface is formed in plants, in the third year - indicators gradually decrease. Every year, the maximum assimilation surface is formed by perennial leguminous herbs to the budding stage - the beginning of flowering (bevel has fallen). The dynamics of leaf surface build-up is directly proportional to the activity of symbiotic relationships with rhizobias. In variants with the highest symbiotic activity (In-1800 and N30+In) the area of leaves reaches maximum values and exceeds 40 thousand m ?/ha in certain years.

ФОРМИРОВАНИЕ СИМБИОТИЧЕСКОГО АППАРАТА ЛЮЦЕРНЫ В ЗАВИСИМОСТИ ОТ ТИПА АЗОТНОГО ПИТАНИЯ

The experiments were carried out in 2017–2019 in the foothill zone of North Ossetia-Alania (540 m above sea level) on leached chernozem. The effect of the mineral and symbiotrophic types of nitrogen nutrition on the formation of the alfalfa symbiotic apparatus was compared to optimize the cultivation agricultural technique. The experimental design included the following options: control - natural soil fertility; In-1800 - seed treatment with the inoculum of nitrogen-fixing bacteria strains selected in high mountain conditions (1800 m above sea level); Strain 425a - seed inoculation with an industrial strain of rhizotorphin (strain 425a); N30 - starting dose of nitrogen; N30+In - combined use of high-mountain strains of bacteria and starting doses of nitrogen. Seeds were treated with the studied strains before sowing. The formation of nodules on the roots of alfalfa during inoculation of seeds with rhizobia strains occurred 1 ... 2 days earlier than in the control, which indicates their greater activity compared to the local microflora. The duration of the general symbiosis in the second year of life in the variants with inoculation with industrial and alpine strains reached 215 ... 216 days, which is 4 ... 7 days more than in the control and variant N30. The greatest number of nodules in all years was noted during seed treatment with the inoculum of alpine rhizobia strains, both in pure form (96 ... 248 units/plant.), and against the background of the use of starting doses of nitrogen (80 ... 243 units/plant.). The smallest mass of nodules in the experiment (40 ... 255 kg/ha) was recorded in the control and variant N30. The highest mass of nodules was formed by the second crop of the second year of sowing life and exceeded 300 kg/ha in all variants with pre-sowing seed inoculation with active rhizobia strains. The superiority of the In-1800 variant over control was 28.3%, and the differences with N30+In turned out to be insignificant.&#x0D; .

Effect of nitrogen fixing bacteria and moringa leaf extract on fruit yield, estragole content and total phenols of organic fennel

The pharmaceutical manufacturer demand of organic medical and aromatic plants has strongly increased during the past decade. Therefore, using biostimulants to improve plant growth is a key factor in organic agriculture. The efficiency of three strains of nitrogen-fixing bacteria (NFB), two concentrations of moringa leaf extract (MLE) and their combinations have been evaluated on fennel plant growth, yield, and oil components. Plant height, branch number per plant, herb fresh weight, fruit weight, umbel number per plant, and fruit yield were significantly enhanced with the application of NFB and/or MLE. Photosynthetic pigments, total phenols, and oil components were also improved. The formation of the undesirable oil component, estragole, has been inhibited simultaneously with an increase in trans-anethole with the application of NFB, particularly Bacillus polymyxa (NFB1). Contrary, estragole content was dominant, in comparison to trans-anethole, with the MLE application. In this regard, the most pronounced effect was noticed with the combined application of Azotobacter chroococcum (NFB2) and MLE2. It could be concluded that using NFB as a biofertilizer without MLE is recommended for organic fennel production, in terms of fruit yield and oil quality.

The efficiency of fertilizers and bacterial preparations on safflower in the risk farming area of the Rostov region

The article presents the results of field experiments on the effect of mineral fertilizers and bacterial preparations on the yield and quality of safflower seeds. Studies were conducted in 2016-2018 in the North-Eastern zone of the Rostov region on dark chestnut soils. The object of research was the variety of safflower Zavolzhsky-1. Predecessor was winter wheat. As mineral fertilizers, ammonium nitrate and ammophos were used in various doses, according to the scheme of experience, which were introduced simultaneously with sowing or randomly for presowing cultivation. The bacterial preparations were presented to the associative nitrogen-fixing bacteria of the strains Minorin, Flavobacterium, KL-10 production research center of Pushkin. In the field experiment, the variants of the joint application of mineral fertilizers and pre-sowing treatment of seeds with bacterial preparations were also studied. The control was an option without the use of mineral fertilizers and bacterial preparations. The research methodology is standard for studying the action of fertilizers. The average seed yield of safflower on the options amounted to 1,03-1,22 t/ha, oil content of seeds of 35.9-36.3 percent, and the yield of oil yield of seeds from 1 ha – 337-398 kg. In the course of research, we have found that the optimal dose of mineral fertilizers, providing the greatest yield and yield of oil in harvest – introduction of scattering under the sowing cultivation at a dose of N48P52. The increase to the control variant was 18.4%. The yield of oil was increased by 23.7%. The bacterial preparation with associative strains of nitrogen-fixing bacteria for use on natural background fertility of the soil Flavobacterium was identified. The increase in the yield of oilseeds was 13.6%, oil collection was 18.1%.&#x0D; &#x0D;

Nitrogen fixation and carbon assimilation of the desert legume Tephrosia apollinea under PEG-induced osmotic stress

Tephrosia apollinea (Leguminosae) is a desert legume shrub from UAE deserts and can fix atmospheric nitrogen through Rhizobium symbiosis. Uniform seedlings of T. apollinea were hydroponically grown in beakers (100 ml) covered with sink strainers in a growth chamber and subjected to different levels of polyethylene glycol (PEG) (0%, 5%, 10%, and 15%) treatment. Potential PEG-induced osmotic stress was evaluated through several plasticity traits such as plant biomass, root nodulation and viability of nodules, and stable isotopes of carbon (δ13C) and nitrogen (δ15N). Osmotic stress decreased plant fresh (FW) and dry biomass (DW), with the largest reduction being found at 15% PEG. Osmotic stress significantly decreased δ13C in both roots and leaves, but the reduction was more prominent in the roots. Conversely, osmotic stress significantly increased δ15N in both roots and leaves. We identified four different strains of nitrogen fixing bacteria (Rhizobium leguminosarum, R. radiobacter, R. meliloti and Bradyrhizobium sp.) from root nodules forming a symbiotic association with T. apollinea. The overall results indicate that carbon allocation, root nodule activity, and carbon and nitrogen isotope signatures are useful functional attributes to measure in relation to adaptive survival of T. apollinea in arid deserts. In addition, the combination of ecophysiological and morphological plasticity in T. apollinea suggest it as an interesting biomass source and nurse plant in nutrient-poor soils of desert environments.

Bradyrhizobium forestalis sp. nov., an efficient nitrogen-fixing bacterium isolated from nodules of forest legume species in the Amazon.

Three strains of nitrogen-fixing bacteria isolated from nodules of Inga sp. (INPA54BT) and Swartzia sp. (INPA86A and INPA01-91A) in soils under native forest in the Brazilian Amazon were previously identified as belonging to the Bradyrhizobium genus. In this study, these strains were characterized using a polyphasic approach to establish their taxonomic position. The three strains shared more than 99.5% sequence similarity of the 16S rRNA gene with the type strains of five Bradyrhizobium species (B. japonicum USDA 6T, B. liaoningense LMG 18230T, B. ottawaense OO99T, B. subterraneum 58 2-1T and B. yuanmingense LMG 21827T). However, multilocus sequence analysis of two (recA and glnII) or three (atpD, gyrB, and recA) housekeeping genes indicated that these three strains represent a new Bradyrhizobium species, which is closely related to B. subterraneum 58 2-1T and B. yuanmingense LMG 21827T. DNA-DNA hybridization values between INPA54BT and B. subterraneum 58 2-1T and B. yuanmingense LMG 21827T were only 41.5 and 30.9%, respectively. Phenotypic characterization also allowed the differentiation of the novel species from B. subterraneum 58 2-1T and B. yuanmingense LMG 21827T. In the phylogenetic analysis of the nodC and nifH genes, the three strains showed similar sequences that were divergent from those of type strains of all Bradyrhizobium species. We concluded that these strains represent a novel species, for which the name Bradyrhizobium forestalis is proposed, with INPA54BT (= LMG 10044T) as type strain. The G+C content in the DNA of INPA54BT is 63.7mol%.

EFFECT OF BIO-FERTILIZERS AND MOLYBDENUM ON GROWTH AND YIELD OF GREEN BEAN

This experiment was carried out at the fields of the Department of Horticulture and Landscape Gardening, College of Agriculture, University of Baghdad, during the spring season of 2015 to study the effect of nitrogen fixing bacterial bio-fertilizers including Rhizobium phaseoli, Azotobacter chroococcum, and Azospirillum brasilense and molybdenum on growth and yield of green beans. The experiment was conducted according to the randomized complete block design (RCBD) with three replications each included 11 treatments represent the interactions between nitrogen fixing bacteria strains, molybdenum solo application, molybdenum and bacteria strains interactions, in addition to the recommended nitrogen application and control treatment. Results were analyzed using the least significant differences (LSD) test at 5% level of significance. Results showed significant effect of the treatment that included all bacteria strains and Mo (T11) on increasing plant macro elements (N, P, and K) which gave 2.39%, 0.49%, and 2.92%, respectively and Fe and Mo concentrations of 269.67 mg.L-1 and 0.69 mg.L-1, respectively and protein percentage in the pods of 13.98%. in addition, treatment of both R. phaseoli and A. chroococcum (T5) gave the most significant main root length of 36.56 cm while R. phaseoli and A. chroococcum and Mo (T9) gave the largest root surface area of 115.00 cm2 and the highest number of root nods that reached 5.33 nod.plant-1. Moreover, T5 significantly increased plant height, leaf number, shoot dry weight, and pod’s length that reached 54.67 cm, 30.22 leaf.plant-1, 65.56 g.plant-1, and 13.62 cm, respectively. As for the T9, results showed significant increase in the number of pods per plant and plant yield of 51.61 pod.plant-1 and 262.03 g.plant-1, respectively.

RESPONSE OF GREEN BEAN TO NITROGEN FIXING BACTERIAL INOCULATION AND MOLYBDENUM

The experiment was conducted at the fields of the Department of Horticulture and Landscape Gardening, College of Agriculture, University of Baghdad, Aljadrya campus during the spring season of 2015 to study the response of green beans to the inoculation with nitrogen fixing bacteria including Rhizobium phaseoli, Azotobacter chroococcum, and Azospirillum brasilense and molybdenum. The experiment was carried out according to the randomized complete block design (RCBD) with three replications each included 11 treatments represent the interactions between nitrogen fixing bacteria strains, molybdenum solo application, molybdenum and bacteria strains interactions, in addition to the recommended nitrogen application and control treatment. Results were analyzed using the least significant differences (LSD) test at 5% level of significance. Results showed that treatment with all three bacteria strains and Mo (T11) gave the most significant value of leaf area and N, P, Fe, Mo in the pods which gave 59.50 dm2.plant-1, 2.24%, 0.25%, 51.67 mg.kg-1, and 0.34 mg.kg-1, respectively. However, treatment with nitrogen (T2) significantly increase potassium percentage in plant pods, root branching, and leaf chlorophyll content that reached 1.71%, 12.11 branch.plant-1, and 147.98 mg.100 g-1 fresh weight. Moreover, treatment with both R. phaseoli and A. chroococcum (T5) gave the highest root dry weight of 7.78 g.plant-1 while the treatment with both R. phaseoli and A. chroococcum and Mo (T9) gave the highest root nodular fresh weight of 633.51 mg.plant-1. Treatments with R. phaseoli alone (T4) and with both R. phaseoli and A. chroococcum (T5) significantly increased shoot number that reached 4.11 shoot.plant-1 while treatment with all bacteria strains (T7) yielded the highest pod’s weight of 5.91 g. As for the total yield, treatment with both R. phaseoli and A. chroococcum and Mo showed to significantly increase total production that gave 20.96 Ton.Ha-1.

Potassium solubilization in phonolite rock by diazotrophic bacteria

Some strains of nitrogen fixing bacteria, besides fixing the N2, can produce phytohormones, control pathogens, act in solubilization of minerals containing phosphorus (P) and potassium (K), contributing to plant growth. However, the solubilization of minerals containing K has been little exploited. Therefore, the aim of this study was to evaluate potassium solubilization (K) of phonolite rock by strains of associative nitrogen fixing bacteria supplied with two different carbon sources. Twelve bacterial strains were cultured for seven days at 25°C in Aleksandrov medium supplemented with phonolite rock powder. The experiment was carried out in a completely randomized factorial design, 13 x 2 (12 bacterial strains and a control without inoculation) and two carbon sources (glucose and sucrose) with four repetitions. After the growth, the supernatant was separated by centrifugation and analyzed for the final pH value and the content of K. All diazotrophic bacteria strains contributed to increase the release of K when compared to the control treatment. The strain UNIFENAS 100-94 solubilized 130 mg L-1 K in the presence of the two carbon sources, indicating the potential use of these diazotrophic bacterial strains for K solubilization from minerals.

Nitrogen-fixing bacteria and arbuscular mycorrhizal fungi in Piptadenia gonoacantha (Mart.) Macbr.

The family Leguminosae comprises approximately 20,000 species that mostly form symbioses with arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB). This study is aimed at investigating and confirming the dependence on nodulation and biological nitrogen fixation in the specie Piptadenia gonoacantha (Mart.) Macbr., which belongs to the Piptadenia group. Two consecutive experiments were performed in a greenhouse. The experiments were fully randomized with six replicates and a factorial scheme. For the treatments, the two AMF species and three NFB strains were combined to nodulate P. gonoacantha in addition to the control treatments. The results indicate this species’ capacity for nodulation without the AMF; however, the AMF + NFB combinations yielded a considerable gain in P. gonoacantha shoot weight compared with the treatments that only included inoculating with bacteria or AMF. The results also confirm that the treatment effects among the AMF + NFB combinations produced different shoot dry weight/root dry weight ratios. We conclude that AMF is not necessary for nodulation and that this dependence improves species development because plant growth increases upon co-inoculation.

Resposta do feijão-caupi a estirpes fixadoras de nitrogênio em Gurupi-TO

Este estudo avaliou o efeito da inoculação com cepas fixadoras de nitrogênio na cv. Caupi de Vinagre em condições do sul do estado do Tocantins. O experimento foi realizado na safra 2007/2008. O delineamento experimental foi em blocos casualizados, com sete tratamentos e quatro repetições. Foram testados cinco inoculantes de bactérias: BR3301, BR3302, BR3262, BR3267 e BR3299, dois controles, um com NPK e um controle sem fertilização ou inoculação. Aos 35 e 55 dias após a emergência foram avaliadas as seguintes variáveis: número de nódulos, massa seca dos nódulos, massa seca dos brotos e eficiência relativa. No final do ciclo foi avaliado o número de vagens por planta, o peso das vagens por planta e o rendimento de grãos. Os dados foram submetidos à análise de variância pelo teste F e as médias foram agrupadas por Scott-Knott, ambas com 5% de probabilidade. A associação entre as médias foi avaliada pela correlação de Pearson. A cepa BR3302 apresentou maior peso seco dos nódulos aos 35 e 55 DAE, porém o controle sem fertilização ou inoculação e o NPK contribuíram para maior produtividade de grãos. O número de vagens e o peso das vagens por planta foram as variáveis ​​que mais influenciaram o rendimento. É necessário um estudo mais aprofundado sobre a seleção de linhagens de bactérias fixadoras de nitrogênio às condições ecológicas do estado do sul do Tocantins.

Co-inoculation with phosphate-solubilzing and nitrogen-fixing bacteria on solubilization of rock phosphate and their effect on growth promotion and nutrient uptake by walnut

The aim of this work was to evaluate effects of co-inoculation with phosphate-solubilizing bacteria (PSB) and nitrogen-fixing bacteria (NFB) on solubilization of rock phosphate (RP) and their effect on growth promotion and nutrient uptake by walnut seedlings. Two PSB strains, Pseudomonas chlororaphis and Bacillus megaterium, and two NFB strains, Arthrobacter pascens and Burkholderia cepacia, were selected to investigate interaction between PSB and NFB in liquid medium. The maximum concentration of soluble phosphorus (P) was determined in the mixing culture of P. chlororaphis and A. pascens. A strong correlation was found between pH and soluble P concentration, as well as the total organic acid production and P solubilization. Co-inoculation with P. chlororaphis and A. pascens amendment with RP resulted in the highest plant height, shoot and root dry weight, P and nitrogen (N) uptake of walnut seedlings, and the maximum amounts of available P and N in soils under shade house conditions. However, mixed inoculation with B. megaterium and A. pascens failed to increase these parameters. The results demonstrated that co-inoculation with PSB and NFB amendment with RP could be a promising and alternative option for utilizing this potent source as P fertilizer in walnut plants and maintaining greater nutrient availability in soils.

Indole-3-Acetic Acid (IAA) Production in Symbiotic and Non-Symbiotic Nitrogen-Fixing Bacteria and its Optimization by Taguchi Design

Production of Indole-3-acetic acid (IAA) in 35 different symbiotic and non-symbiotic nitrogen-fixing bacteria strains isolated from soil and plant roots was studied and assayed by chromatography and colorimetric methods. These bacteria included Agrobacterium, Paenibacillus, Rhizobium, Klebsiella oxytoca, and Azotobacter. The best general medium and synergism effects of isolates for IAA production were investigated. Effects of different variables containing physical parameters and key media components and optimization of condition for IAA production were performed using the Design of Experiments. Qualitek-4 (W32b) software for automatic design and analysis of the experiments, both based on Taguchi method was used. The results showed that Rhizobium strains, symbiotic, and Paenibacillus non-symbiotic bacteria yielded the highest concentrations of IAA (in the range of 5.23-0.27 and 4.90-0.19 ppm IAA/mg biomass, respectively) and IAA production was increased by synergism effect of them. Yeast Extract Mannitol medium supplemented with L-tryptophan was the best general medium for IAA production. The analysis of experimental data using Taguchi method indicated that nitrogen source is very prominent variable in affecting the yield and mannitol as carbon source, potassium nitrate (1%), and L-tryptophan (3 g/l) as nitrogen sources after 72-h incubation at 30 degrees C were the optimum conditions for production of IAA. 5.89 ppm IAA/mg biomass was produced under these optimal conditions.

Molecular characterization of nitrogen-fixing bacteria isolated from brazilian agricultural plants at São Paulo state

Fourteen strains of nitrogen-fixing bacteria were isolated from different agricultural plant species, including cassava, maize and sugarcane, using nitrogen-deprived selective isolation conditions. Ability to fix nitrogen was verified by the acetylene reduction assay. All potentially nitrogen-fixing strains tested showed positive hybridization signals with a nifH probe derived from Azospirillum brasilense. The strains were characterized by RAPD, ARDRA and 16S rDNA sequence analysis. RAPD analyses revealed 8 unique genotypes, the remaining 6 strains clustered into 3 RAPD groups, suggesting a clonal origin. ARDRA and 16S rDNA sequence analyses allowed the assignment of 13 strains to known groups of nitrogen-fixing bacteria, including organisms from the genera Azospirillum, Herbaspirillum, Pseudomonas and Enterobacteriaceae. Two strains were classified as Stenotrophomonas ssp. Molecular identification results from 16S rDNA analyses were also corroborated by morphological and biochemical data.

BIOPREPARATIONS IN BIOORGANIC AGRICULTURE

The results of investigations of Ukrainian and Russian scientists- microbiologists as for creation of microbic preparations and their ap¬plication in bioorganic agriculture are generalized. The major factors and the scheme of biotechnological manufacturing of specified biologi¬cal products are considered. It has been shown, that one of the most important properties of the preparation is the form of manufacturing. Searching of universal fills is very actual as well as different updatings of biological products which provide maximal adaptibility of biological agents to specific conditions, depending on regions. For the first time gel, lignin and vermiculturas forms of biological products based on new strains of nitrogen fixing bacteria have been developed by Ukrainian scientists.

Stimulation of nitrogen fixation in soddy-podzolic soils with fungi

Stimulation of nitrogen fixation in soddy-podzolic soils is related to the hydrolytic activity of fungi decomposing plant polymers. It was found that the rate of nitrogen fixation upon the simultaneous inoculation of the strains of nitrogen-fixing bacteria Bacillus cereus var. mycoides and the cellulolytic fungus Trichoderma asperellum into a sterile soil enriched with cellulose or Jerusalem artichoke residues is two to four times higher than upon the inoculation of the strains of Bacillus cereus var. mycoides L1 only. The increase in the nitrogen fixation depended on the resistance of the substrates added into the soil to fungal hydrolysis. The biomass of the fungi decomposing plant polymers increased by two–four times. The nitrogen-fixing activity of the soil decreased when the growth of the fungi was inhibited with cycloheximide, which attested to a close correlation between the intensity of the nitrogen fixation and the decomposition of the plant polymers by fungi. The introduction of an antifungal antibiotic, together with starch or with plant residues, significantly (by 60–90%) decreased the rate of nitrogen fixation in the soll.

Nitrogen fixation by hydrogen-utilizing bacteria.

Seventeen strains of nitrogen-fixing bacteria, isolated from different habitats on hydrogen and carbon dioxide as well as on other substrates, morphologically resembled each other. All strains, including Mycobacterium flavum 301, grew autotrophically with hydrogen. The isolate strain 6 was sensitive to oxygen when dependent on N2 as nitrogen source, a consequence of the sensitivity of its nitrogenase towards oxygen. At the same time, strain 6 was sensitive to hydrogen when growing autotrophically on N2 as nitrogen source, but hydrogen did not affect acetylene reduction by these cells.