Azotobacter Cultures Research Articles

Динамика развития азотобеспечивающих бактерий на почвах Гянджа-Казахской природно-экономической зоны (Азербайджан)

The study of the nitrogen cycle in nature is of great importance, because as a result of anthropogenic impacts the small changes cause the chemical pollution of the soil. The effect of anthropogenic and environmental factors to the productivity of azotobacter cultures on the soils of the Ganja-Gazakh natural economic zone has been described in the article.

Role and perspective of Azotobacter in crops production

<p>Low nitrogen content in soil is usually overcome by chemical fertilization. After long application period, high-dose and intensive use of N fertilizers can cause ammonia volatilization and nitrates accumulation in soil. In sustainable agriculture, the use of bacterial inoculant integrated with nutrient management system has a role in soil health and productivity. Azotobacter-based biofertilizer is suggested as a chemical nitrogen fertilizer substitute or addition in crop production to improve available nutrients in the soil, provide some metabolites during plant growth, and minimize fertilizer doses. The objective of this literature reviewed paper is to discuss the role of Azotobacter in agriculture; and the prospective of Azotobacter to increase yield and substitute the chemical fertilizer in food crops production. The results revealed that mechanisms by Azotobacter in plant growth enhancement are as biofertilizer, biostimulant, and bioprotectant. Nitrogen fixation by Azotobacter is the mechanism to provide available nitrogen for uptake by roots. Azotobacter stimulates plant growth through phytohormones synthesis; indole acetic acid, cytokinins, and gibberellins are detected in the liquid culture of Azotobacter. An indirect effect of Azotobacter is exopolysaccharide production and plant protection. Inoculation of Azotobacter in the field integrated with organic matter and reduced chemical fertilizer are reported to improve plant growth and yield.</p>

Effect of Azotobacter and Sphingobacterium species on guava seedlings under nursery conditions

An experiment was planned to study the effect of biofertilizers, namely Azotobacter and Sphingobacteriumspecies on guava seedlings under nursery conditions. The standard culture of Azotobacter and Sphingobacteriumspecies was obtained from Department of Microbiology, Punjab Agricultural University, Ludhiana, Punjab, India. The liquid formulations of microbial inoculants were prepared by supplementing 2% PEG in basal medium. Thethree months old guava seedlings were given dip treatment for 30 mins with liquid microbial inoculants andtransplanted in nursery bed and observations were recorded after one year. The treated guava seedlings showedvery good response to Azotobacter and Sphingobacterium species treatment (T3) followed by Azotobacter sp.(T2). Seedlings inoculated with Azotobacter and Sphingobacterium species inoculation showed an increase of 4.28 per cent in shoot length, 4.41 per cent in collar diameter, 14.55 per cent in root length, 3.85 per cent in rootnumbers, 9.33 per cent in number of main branches/plant, 7.95 per cent in number of leaves, 6.95 per cent infresh weight of shoot, 8.27 per cent in dry weight of shoot, 15.08 per cent in fresh leaf weight, 14.08 per cent indry weight of leaves, 12.60 per cent in fresh weight of root and 12.69 per cent in dry weight of root over control. The use of biofertilizer offers better options for enhancing the vegetative growth of horticultural crops undernursery conditions in an increasingly eco-conscious world, thus increasing the success rate of vegetative propagation in healthy plants with well developed root and shoot system.

Elucidating the interactions and phytotoxicity of zinc oxide nanoparticles with agriculturally beneficial bacteria and selected crop plants.

There is a growing interest in the use of bioinoculants to assist mineral fertilizers in improving crop production and yield. Azotobacter and Pseudomonas are two agriculturally relevant strains of bacteria which have been established as efficient bioinoculants. An experiment involving addition of graded concentrations of zinc oxide (ZnO) nanoparticles was undertaken using log phase cultures of Azotobacter and Pseudomonas. Growth kinetics revealed a clear trend of gradual decrease with Pseudomonas; however, Azotobacter exhibited a twofold enhancement in growth with increase in the concentration of ZnO concentration. Scanning electron microscopy (SEM), supported by energy-dispersive X-ray (EDX) analyses, illustrated the significant effect of ZnO nanoparticles on Azotobacter by the enhancement in the abundance of globular biofilm-like structures and the intracellular presence of ZnO, with the increase in its concentration. It can be surmised that extracellular mucilage production in Azotobacter may be providing a barrier to the nanoparticles. Further experiments with Azotobacter by inoculation of wheat and tomato seeds with ZnO nanoparticles alone or bacteria grown on ZnO-infused growth medium revealed interesting results. Vigour index of wheat seeds reduced by 40-50% in the presence of different concentrations of ZnO nanoparticles alone, which was alleviated by 15-20%, when ZnO and Azotobacter were present together. However, a drastic 50-60% decrease in vigour indices of tomato seeds was recorded, irrespective of Azotobacter inoculation.

Integrated Effect of Rhizobium and Azotobacter Cultures on the Leguminous Crop Black Gram (Vigna mungo)

A pot experiment was performed to evaluate the integrated effect of Rhizobium and Azotobacter sp. on the plant growth, nodule appearance, no of leaf, shoot length, root length, chlorophyll contents and carbohydrate content in black gram during 2016 growing period at the Department of Microbiology, Dr. Ram Manohar Lohia Avadh University Faizabad, UP, India. Different treatments viz., T1: Control (Sterile soil+Seeds without culture treatment), T2: Sterile Soil and Seeds both are treated with Azotobacter sp., T3: Sterile Soil and Seeds both are treated with Rhizobium sp., T4: Sterile Soil and Seeds both are treated with mixed culture of Azotobacter sp. and Rhizobium sp., T5: Sterile Soil+Seeds treated with Azotobacter sp., T6: Sterile Soil + Seeds treated with Rhizobium sp., T7: Sterile Soil+Seeds treated with mixed culture of Azotobacter sp. and Rhizobium sp. All experiments were carried out in triplicate set. The T4 treatment showed maximum shoot length (51.6 cm), root length (17.3 cm), fresh and dry shoot biomass (12.99 and 3.21 g), fresh and dry root biomass (3.54 and 0.99 g), no. of leafs (20.4), root nodules per plant (18.2) and chlorophyll content (1.3 mg/g) and reducing (867.4 μg/g) and non-reducing sugar (1905.5 μg/g) content per plant biomass respectively. The Azotobacter and Rhizobium sp. have friendly associations and they have different physiology and habitat. Therefore, they help plant growth promotion by them own system. Therefore, such combination can be recommended for field application for sustainable agriculture. Excessive application of chemical fertilizers causes environmental and economic problems; hence the use of PGPR and Rhizobium bacteria can be acceptable due to cut contribution expenditure, increase in grain yield and environmental friendly.

Isolation and Molecular Characterization of Heavy Metal-Resistant Azotobacter chroococcum from Agricultural Soil and Their Potential Application in Bioremediation

Pollution of soil with heavy metals, herbicides, antibiotics and other chemicals is known to have a negative effect on microbial activities. Therefore, the aim of this study was to isolate cultures of Azotobacter sp. from polluted and unpolluted soils and to study the effect of these pollutants on their growth. A total of 120 Azotobacter sp. were isolated from soils irrigated with wastewater (contaminated soils) and groundwater (uncontaminated soils). These isolates were screened for resistance to heavy metals, herbicide and antibiotics. Also, the soils from which the cultures were isolated were analyzed for the concentrations of Zn2+, Cd2+, Cu2+, Pb2+ and Mn2+ they contained. Contaminated soil showed high levels of heavy metals as compared to uncontaminated soil. The size of the Azotobacter population in contaminated soil was lower than that in uncontaminated soil. Of the Azotobacter isolates, 64 that were recovered from contaminated soil exhibited high resistance to heavy metals (Hg2+, Cd2+, Cu2+, Cr3+, Co2+, Ni2+, Zn2+ and Pb2+) and herbicide 2,4-D compared to 56 isolates from uncontaminated soil. Also, isolates from contaminated soil showed high resistance to chloramphenicol, nitrofurantoin and co-trimoxazole compared to those isolated from uncontaminated soil. The majority of Azotobacter isolates from contaminated soil showed multiple-resistance to different metal ions and antibiotics. All isolates failed to grow at pH less than 6. Salt concentration (5%) was found to be inhibitory to all isolates. The most potent isolates from contaminated soil that showed multiresistance to all substances tested were identified on the basis of morphological and biochemical characteristics, and 16S rRNA as A. chroococcum. These resistant isolates could be employed in contaminated soils and/or bioremediation.

English

This study was designed to evaluate the effects of three pesticides (Imazetapir, Dimethoate and Bayleton 50) at the recommended concentration (in the field), on the growth of pure cultures ofAzotobacter chroococcum and Azotobacter vinelandii, on the amount of fixed nitrogen and nifgenes. Herbicide Imazetapir had no negative effect on nitrogen fixing bacteria, while Dimethoate and Bayleton 50 exhibited inhibitory effect on growth. Same effects were obtained on fixed nitrogen obtained when treated with studied pesticides. nifH1, nifH2, nifH3, nifU and nifV from A. chroococcum, and nifH, nifK, nifD, and nifM gene in A. Vinelandii were lost when pots were cultivated with wheat and treated with both Dimethoate and Bayleton 50, therefore, be deemed highly susceptible to them. While herbicide did not affect the nif genes, the bands on gel electrophoresis appeared as normal sample.   Key words: Azotobacter chroococcum, Azotobacter vinelandii, fungicide (Bayleton 50), herbicide (Imazetapir), insecticide (Dimethoate).

Biological removal of Cr (VI) by bacterial isolates obtained from metal contaminated sites

Present study demonstrates the application of indigenous bacteria and pure culture of Azotobacter for removal of Cr (VI) from the aqueous solution and industrial effluent. Minimum inhibitory concentration (MIC) was determined for 3 bacterial isolates (B1, B2, B3) and pure culture of Azotobacter. The effect of various parameters such as effect of initial Cr (VI) concentration, biomass dose, and time were examined to study the biosorption and bioaccumulation separately using live and dead cells, respectively. It was found that bacterial isolate B2 showed maximum Cr (IV) removal capacity (102 mg g −1 biomass, dry weight) at initial Cr (VI) concentration of 150 mg/L. Langmuir and Freundlich isotherm model was applied, which gave a good representation of the experimental equilibrium concentrations for the biosorption of Cr (VI). During bioaccumulation process also live bacterial strain B2 showed maximum bioaccumulation i.e., 106 mg g−1 at initial Cr (VI) concentration of 150 mg/L at pH 4.0. Bioaccumulation process was found to be time dependent since removal of Cr (VI) increased with time and equilibrium state was reached at 72–96 hours. This study demonstrates the potential of indigenous bacterial strains isolated from the contaminated site for evolving eco-friendly treatment for small-scale industrial effluent.

Effect of Azotobacter cultures in relation to nitrogen application on growth, yield and alkaloidal composition of opium poppy (Papaver somniferum)

A study conducted during 1987-91 to study the effect ofAzotobacter cultures M 4, W 5 on Jawahar Aphim 16 and Trishna (IC 42) varieties ofopium poppy (Papaver somniferum L.) grown at Delhi. It increased the yield parameters and these were at par with 40 kg Nlha. The Azotobacter cultures were compatible to use in combination with N fertilizer. Of the 2 Azotobacter strains W 5 was superior and its use through dripping gave better response than seed treatments. Further the use of bio-fertilizer saved expenditure on 40 kg Nlha in opium poppy.

Metabolic cost of nitrogen incorporation by N2-fixingAzotobacter vinelandii is affected by the culture pH

N2-fixing continuous cultures ofAzotobacter vinellandii ATCC 9046 were carried out under various dissolved oxygen tensions (2, 25 and 50% air saturation) and, for each of these oxygen concentrations, the culture pH was controlled at 6.2 and 7.4. The culture pH exerted a profound influence on the specific consumption rates of glucose and oxygen and on the growth yields. Parallely, the total metabolic cost for N-incorporation was affected: for incorporating a given amount of N an extra glucose consumption of more than 70% took place when the culture pH was changed from 7.4 to 6.2. This effect was observed when the dissolved oxygen tension in the cultures was 25 or 50% but was less pronounced when it was 2% air saturation.

Azotobacter vinelandii flavodoxin: purification and properties of the recombinant, dephospho form expressed in Escherichia coli

The nifF gene coding for the flavodoxin from the nitrogen-fixing bacterium Azotobacter vinelandii (strain OP) was cloned into the plasmid vector pUC7 [Bennett, L. T., Jacobsen, M. R., & Dean, D. R. (1988) J. Biol. Chem. 263 1364-1369] and the resulting plasmid transformed and expressed in Escherichia coli strain DH5. Recombinant Azotobacter flavodoxin is expressed at levels 5-6-fold higher in E. coli than in comparable yields of Azotobacter cultures grown under nitrogen-fixing conditions. Even higher levels were observed with flavodoxin expressed in E. coli under control of a tac promoter. Electron spin resonance spectroscopy on whole cells and in cell-free extracts showed the flavodoxin to be largely in the semiquinone form. The flavodoxin purified from E. coli exhibited the same molecular weight, isoelectric point, flavin mononucleotide (FMN) content, N-terminal sequence, and carboxyl-terminal amino acids as for the wild-type Azotobacter protein. The recombinant flavodoxin differed from native flavodoxin in that it exhibited an increased antigenicity to flavodoxin antibody and did not contain a covalently bound phosphate. Small differences are also observed in circular dichroism spectral properties in the visible and ultraviolet spectral regions. The recombinant, dephospho flavodoxin exhibits an oxidized/semiquinone potential (pH 8.0) of -224 mV and a semiquinone/hydroquinone couple (pH 8.0) of -458 mV. This latter couple is 50-60 mV higher than that exhibited by the native flavodoxin. Resolution of recombinant dephospho flavodoxin resulted in an apoflavodoxin that was much less stable than that prepared from the native protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Fungi on Seed Germination in Association with Azotobacter

Summary Azotobacter cultures which were studied for their fungistatic action towards Alternaria tenuis (5 cultures), Curvularia spec. (5 cultures), and Helminthosporium spec. (4 cultures) were taken up in this study to assess the combined effect of these organisms ( Azotobacter and fungi) on germination of seeds of Jowar, maize, wheat, and paddy by using 200 seeds lot in each case (50 in maize) along with the control. The results show that only 2 out of 5 Alternaria tenuis , 2 out of 5 Cuvcularia spec, and 2 out of 4 Helminthosporium spec, could increase germination in association with Azotobacter .

Associative Effect of Mixed Cultures of Azotobacter and Different Rhizosphere Fungi with Rhizobium japonicum on Nodulation and Symbiotic Nitrogen Fixation of Soybean

Summary The associative effect of mixed cultures of Azotobacter and different rhizosphere fungi with Rhizobium japonicum on nodulation and symbiotic nitrogen fixation of soybean (Glycine max) was studied. It was found that mixed cultures of Azotobacter caused increase in root nodules, nodules fresh weight, dry weight of plant, and symbiotic nitrogen fixation. On the other hand, the mixed culture of rhizosphere fungi showed decrease in nodulation and symbiotic nitrogen fixation with the exception of Fusarium moniliforme, which revealed slight increase in nodulation and symbiotic nitrogen fixation. The organisms used in this study were also tested for growth-promoting substances. It was found that both Azotobacter and rhizosphere fungi synthesized in their culture medium gibberellin (GA3) and indole acetic acid (IAA).

Fungistatic Action of Azotobacter chroococcum and A. vinelandii on Different Fungi

Summary The sixty fungi tested, belonging to pathogenic and non-pathogenic genera, interacted with Azotobacter in both directions, viz., stimulation as well as inhibition of growth. Most of the Azotobacter cultures of both the species were active against Altemaria, Curvularia, Fusarium, Rhizoctonia, Helminthosporium , and Verticillium . At the same time 17 out of 20 cultures of Azotobacter were inhibited by Aspergillus sp. (PS-1) and all the 20 cultures by Aspergillus sp. (KR-31). Penicillium commune (D-16) inhibited the growth of all Azotobacter cultures; three cultures of Trichoderma (S-1, No. 2, and M-2) had inhibitory effect on all the 20 cultures of Azotobacter .

Enhanced nodulation of leguminous plant roots by mixed cultures ofAzotobacter vinelandii and rhizobium

Azotobacter vinelandii strains caused the formation of increased numbers of root nodules onGlycine max, Vigna unguiculata andTrifolium repens by their respective rhizobial symbionts. Increased nodulation due to inoculation withA. vinelandii also occurred in field grownG. max. Mutant strains ofA. vinelandii unable to fix nitrogen caused nodulation increases comparable to those caused by nitrogen-fixing strains. This indicates that nitrogen fixation byA. vinelandii was not responsible for the enhanced nodulation. The effect ofA. vinelandii on nodulation was greatest when cells from the mid-exponential phase of growth were applied as inoculants. Non viable cell preparations ofAzotobacter vinelandii were also found to cause an increase in the number of root nodules formed onGlycine max Rhizobium japonicum under greenhouse conditions. The nodulation enhancement activity was influenced by the method chosen to kill theA. vinelandii cells. Heat treatment and treatment with lethal levels of streptomycin destroyed the activity, whereas the activity was unaffected by ultraviolet-light treatment of the cells. Cell-free extracts ofA. vinelandii were found to enhance nodulation. On the other hand, culture supernatants ofA. vinelandii had no effect on nodulation. A split-root experiment suggested that the agent(s) responsible for the increased nodulation was not translocatable throughout the plant. The results suggest a non-excretable protein, produced byA. vinelandii, as a possible mechanism for nodulation enhancement.

Influence of solar eclipse on the growth and nodulation by Rhizobium and nitrogen fixation by Azotobacter

It was noted that, when pure cultures of Rhizobium and Azotobacter were exposed to the solar eclipse, there was sudden destruction of cells up to 30 per cent over the unexposed control. Nodulation and nitrogen fixation was also considerably affected. Wenn Reinkulturen von Rhizobium und I einer Sonnenfinsternis (New Delhi, 16. 2. 1980) ausgesetzt wurden, erlitten sie eine plötzliche Zerstörung ihrer Zellen bis zu 30%. Knöllchenbildung und Stickstoffixierung waren ebenfalls beträchtlich herabgesetzt.

Effect of Azotobacter on germination of spores of different fungi

Summary Azotobacter cultures which were studied for their fungistatic action towards different plant pathogenic fungi in iquid medium were used to assess their effect on spore germination of Alternaria (5 cultures), Curvularia (5 cultures) Corynespora (1 culture), Fusarium (3 cultures) and Helminthosporium (4 cultures). The germination percentage was recorded at the end of 6 hours at 30 °C.

Association Between Azotobacter and Other Soil Bacteria and Its Effect On Nitrogen Fixation

The association between A. vinelandii and either Agrobacterium sp. or Micrococcus sp., which are usually found as contaminants in Azotobacter cultures, was investigated. In comparison with pure cultures, association increased the microbiol counts in addition to increasing nitrogen fixation rates and efficiency. In liquid cultures higher Azotobacter densities were observed in the top 5 cm of the column concomitant with lowering the economic coefficient of utilization of carbonaceous compounds, which resulted in low efficiency of nitrogen fixation. In deep layers, lower amounts of nitrogen gain were obtained, but higher efficiencies of N2-fixation were recorded. In sand cultures, the biggest amounts of fixed nitrogen were in the 5--15 cm layer of the soil column and in deeper layers economic utilization of sugars occurred, but nitrogen gain sharply decreased.

Studies on the aerobic non-symbiotic nitrogen-fixing bacteria, other than Azotobacter, in Egyptian soils

Twenty isolates of micro-organisms capable of growing on nitrogen-deficient medium and found as contaminants in Azotobacter cultures were isolated from Egyptian soils and studied for their morphological, cultural, and physiological properties. These micro-organisms s are members of Rhizobiaceae, Pseudomonadaceae, Achromobacteriaceae, Enterobacteriaceae, Micrococcaceae, Bacillaceae, and Streptomycetaceae as well as some yeasts. In nitrogen-free medium the micro-organism fixed only small amounts of atmospheric nitrogen, hardly exceeding 3 ppm and because of their low sugar consumption rates, efficiences of N2-fixation sometimes reaching 18 mg nitrogen fixed/g carbon oxidized were recorded. Addition of 15 ppm combined nitrogen to the medium increased the amounts of nitrogen fixed to 3--9 ppm.

Studies on the symbiosis of mixed culture ofAzotobacter and yeast

Azotobacter culture has been investigated in the physiological state in which it fixed molecular nitrogen. A chemically defined medium was formulated that would support the growth ofAzotobacter vinelandii, but not the growth ofSaccharomyces cerevisiae in pure culture, unless a nitrogen source was added. The yeast culture was allowed to grow in mixed culture with the bacterium. Transient and steady-state populations of each organism in mixed culture at various dilution rates were enumerated with hemocytometer under a microscope. The difference in size of the organisms permitted easy resolution. The essential nutrilite, nitrogen, which is fixed by the bacteria and required by yeast caused the yeast to be dependent on the growth of the bacterium. At low dilution rates the yeast population reflected changes in the numbers ofAzotobacter. The numbers ofAzotobacter were identical in pure culture or in mixed culture; thus the interaction can be termed competitive commensalism. In batch culture, yeast had no effect on the rate of nitrogen fixation byAzotobacter. E. Coli ML-30 had a slight inhibitory effect whileC1. pasteurianum exhibited a stimulating effect. In continuous culture at low dilution rates, yeast was found to increase the rate of nitrogen fixation byAzotobacter vinelandii by 4.5%. Differential equations characterizing commensalism in the chemostat have been proposed.