Bacterial inoculation positively affects the quality and quantity of flax under deficit irrigation regimes.

AIM: The present research was conducted to investigate the effect of plant growth-promoting rhizobacteria (PGPR) and deficit irrigation on quality and quantity of flax under field and pot conditions to determine bacterial efficiency and to decrease water deficit effects. METHODS AND RESULTS: Initially, in vitro experiments were performed to determine the growth-promoting characteristics of bacteria. Then in the field, the effects of bacterial inoculation (control, Azotobacter chroococcum, Azospirillum lipoferum, Bacillus amyloliquefaciens, Bacillus sp. strain1 and Pseudomonas putida) on flax traits were evaluated at different irrigation levels (100, 75 and 50% crop water requirement). Bacterial treatments in the pot experiment were selected based on the field experiment results. The irrigation regimes in the pot and field experiments were the same and bacterial treatments included single, doublet and triplet applications of the bacteria. All the bacterial strains could solubilize phosphate, produce ammonia (except for Bacillus sp. strain1), indole acetic acid and siderophore (except P. putida). Field results indicated that the bacteria significantly mitigated the effects of water deficit. Compared with control plants, bacterial treatments increased the oil, linolenic acid, protein and sulphur content; the number of shoots and capsules; and the harvest index in the flax plants. Pot experimental results revealed that the combined inoculations were more effective than single inoculum treatments. CONCLUSIONS: Bacterial inoculation alleviates deficit irrigation effects in flax plants. SIGNIFICANCE AND IMPACT OF THE STUDY: The effectiveness of applying A. chroococcum, B. amyloliquefaciens and Bacillus sp. strain1 was confirmed, especially as a combination to protect flax against water deficit and to improve its nutritional quality and growth.

Bioinoculants play a significant role in shaping the rhizospheric microbial community: a field study with Cajanus cajan.

The present study is an attempt to understand the impact of bioinoculants, Azotobacter chroococcum (A), Bacillus megaterium (B), Pseudomonas fluorescens (P), on (a) soil and plant nutrient status, (b) total resident and active bacterial communities, and (c) genes and transcripts involved in nitrogen cycle, during cultivation of Cajanus cajan. In terms of available macro- and micro-nutrients, triple inoculation of the bioinoculants (ABP) competed well with chemical fertilizer (CF). Their 'non-target' effects were assessed in terms of the abundance and activity of the resident bacterial community by employing denaturing gradient gel electrophoresis (DGGE). The resident bacterial community (16S rRNA gene) was stable, while the active fraction (16S rRNA transcripts) was influenced (in terms of abundance) by the treatments. Quantification of the genes and transcripts involved in N cycle by qPCR revealed an increase in the transcripts of nifH in the soil treated with ABP over CF, with an enhancement of 3.36- and 1.57- fold at flowering and maturity stages of plant growth, respectively. The bioinoculants shaped the resident microflora towards a more beneficial community, which helped in increasing soil N turnover and hence, soil fertility as a whole.

Root inoculation with Azotobacter chroococcum 76A enhances tomato plants adaptation to salt stress under low N conditions.

BACKGROUND: The emerging roles of rhizobacteria in improving plant nutrition and stress protection have great potential for sustainable use in saline soils. We evaluated the function of the salt-tolerant strain Azotobacter chroococcum 76A as stress protectant in an important horticultural crop, tomato. Specifically we hypothesized that treatment of tomato plants with A. chroococcum 76A could improve plant performance under salinity stress and sub-optimal nutrient regimen. RESULTS: Inoculation of Micro Tom tomato plants with A. chroococcum 76A increased numerous growth parameters and also conferred protective effects under both moderate (50 mM NaCl) and severe (100 mM NaCl) salt stresses. These benefits were mostly observed under reduced nutrient regimen and were less appreciable in optimal nitrogen conditions. Therefore, the efficiency of A. chroococcum 76A was found to be dependent on the nutrient status of the rhizosphere. The expression profiles of LEA genes indicated that A. chroococcum 76A treated plants were more responsive to stress stimuli when compared to untreated controls. However, transcript levels of key nitrogen assimilation genes revealed that the optimal nitrogen regimen, in combination with the strain A. chroococcum 76A, may have saturated plant's ability to assimilate nitrogen. CONCLUSIONS: Roots inoculation with A. chroococcum 76A tomato promoted tomato plant growth, stress tolerance and nutrient assimilation efficiency under moderate and severe salinity. Inoculation with beneficial bacteria such as A. chroococcum 76A may be an ideal solution for low-input systems, where environmental constraints and limited chemical fertilization may affect the potential yield.

[Use of Leersia hexandra (Poaceae) for soil phytoremediation in soils contaminated with fresh and weathered oil]. / Uso de Leersia hecandra (Poaceae) en la fitorremediación de suelos contaminados con petróleo fresco e intemperizado.

The oil industry has generated chronic oil spills and their accumulation in wetlands of the state of Tabasco, in Southeastern Mexico. Waterlogging is a factor that limits the use of remediation technologies because of its high cost and low levels of oil degradation. However, Leersia hexandra is a grass that grows in these contaminated areas with weathered oil. The aim of the study was to evaluate the bacteria density, plant biomass production and phytoremediation of L. hexandra in contaminated soil. For this, two experiments in plastic tunnel were performed with fresh (E1) and weathered petroleum (E2) under waterlogging experimental conditions. The E1 was based on eight doses: 6 000, 10 000, 30 000, 60 000, 90 000, 120 000, 150 000 and 180 000 mg.kg-1 dry basis (d. b.) of total petroleum hydrocarbons fresh (TPH-F), and the E2, that evaluated five doses: 14 173, 28 400, 50 598, 75 492 and 112 142 mg. kg-1 d. b. of total petroleum hydrocarbons weathered (TPH-W); a control treatment with 2 607 mg.kg-1 d. b. was used. Each experiment, with eight replicates per treatment, evaluated after three and six months: a) microbial density of total free-living nitrogen-fixing bacteria (NFB) of Azospirillum (AZP) and Azotobacter group (AZT), for viable count in serial plate; b) dry matter production (DMP), quantified gravimetrically as dry weight of L. hexandra; and c) the decontamination percentage of hydrocarbons (PDH) by Soxhlet extraction. In soil with TPH-F, the NFB, AZP y AZT populations were stimulated five times more than the control both at the three and six months; however, concentrations of 150 000 and 180 000 mg.kg-1 d. b. inhibited the bacterial density between 70 and 89 %. Likewise, in soil with TPH-W, the FNB, AZP and AZT inhibitions were 90 %, with the exception of the 14 173 mg.kg-1 d. b. treatment, which stimulated the NFB and AZT in 2 and 0.10 times more than the control, respectively. The DMP was continued at the six months in the experiments, with values of 63 and 89 g in fresh and weathered petroleum, respectively; had no significant differences with the control (p≤0.05). The PDH reached values of 66 to 87 % both TPH-F and TPH-W at six months, respectively. These results demonstrated the ability the L. hexandra rhizosphere to stimulate the high NFB density, vegetal biomass production and phytoremediation of contaminated soils (with fresh and weathered petroleum), in a tropical waterlogging environment.

[THE COMPLEX ESTIMATE OF THE RHIZOBIUM NODULATION ABILITY AND THE FEATURES OF SOYBEAN SYMBIOTIC SYSTEMS FORMATION AT THE MICROBIAL COMPOSITIONS SEED INOCULATION].

The features of the soybean symbiotic systems formation and carry out the complex es- timate of the rhizobium nodulation ability at the seed inoculation of the microbial composi- tions on the bases of nodule bacteria, azotobacter and phytolectins (soybean seeds lectin, wheat germ agglutinin) were studied in the green-house experiments with a soil cultures. It was shown, that complex inoculants accelerate the process of becoming infected of plants by rhizobia in the early stages of soybean development; contribute to the expansion of the spectrum of genetically determined ability of nodule bacteria in the formation of a certain number of nodules on the host plant during the growing season as well as the formation of more root nodules with more of their weight during the second half of the growing season of soybean and significant increase mass of the one nodule and also slow the root nodules aging process at the end of the growing season compared with a rhizobial monoinoculant. It was proposed to use a complex of criteria in the estimating of the rhizobia nodulation ability in the microbial compositions: "nodulation activity", "nodulation range", "the num- ber of nodules on the plant", "mass of nodules per plant", "mass of one nodule", which are indicative for different stages of the symbiosis formation.

Solubilization of tricalcium phosphate by P(3HB) accumulating Azotobacter chroococcum MAL-201.

Cells of Azotobacter chroococcum MAL-201 (MTCC 3853) are capable of accumulating the intracellular poly(3-hydroxybutyric acid) [P(3HB)], accounting for 65-71 % of its cell dry weight and also capable of synthesizing the enzyme alkaline phosphatase (APase), when grown in glucose and tricalcium phosphate containing nitrogen-free modified Stockdale medium. The concentration of insoluble phosphate in broth medium was optimized as 0.25 % (w/v) for growth and biosynthesis of APase. However, the suboptimal concentration of phosphate (0.1 %, w/v) appeared as the best suited for accumulation of P(3HB) by the strain. The significant differences were observed in biosynthesis of polymer and APase enzyme under variable phosphate concentrations. Glucose, 3.0 % (w/v) was recorded as the optimum concentration for all of the three parameters. The continuation of APase biosynthesis was observed during the period of significant decline in the cellular content of the polymer in the late phase of growth. In order to study the role of P(3HB), the rate of autodigestion of biopolymer and phosphate solubilization rate (k, mineralization constant) were determined in carbon-free medium under batch cultivation process and the parameters were found to be positively correlated. The maximum phosphate solubilization rate (k = 0.0154) by the strain MAL-201 timed at the 10th hour of incubation when the rate of polymer degradation concomitantly attained its peak corresponding to 87 mg/l/h and then declined gradually. Only a negligible amount of residual polymer remained undigested. These data strongly support the functional role of P(3HB) in response to multinutritional stress condition.

Novel cereal bran based low-cost liquid medium for enhanced growth, multifunctional traits and shelf life of consortium biofertilizer containing Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.

The present study was carried out to valorise cereal (rice and wheat) bran for the development of low-cost liquid consortium bioformulation. Different concentrations of bran-based liquid media formulations were evaluated for the growth of consortium biofertilizer cultures (Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.). Among the bran-based formulations, wheat bran-based formulation WB5, exhibited the highest viable cell of 10.68 ± 0.09 Log10 CFU/ml and 12.63 ± 0.04 Log10 CFU/ml for Azotobacter chroococcum and Bacillus subtilis whereas for Pseudomonas sp., rice bran based bioformulation RB5 recorded maximum viability (12.71 ± 0.05 Log10 CFU/ml) after 72 h of incubation. RB51 and WB52liquid formulations were further optimized for enhanced shelf life using 5, 10 and 15 mM of trehalose, 0.05 and 0.1% carboxymethyl cellulose, and 0.5 and 1.0% glycerol. Following the peak growth at 72 h of incubation, a gradual decrease in the viable population of consortium biofertilizer cultures was observed in all the liquid formulations. The WB5 and RB5 formulations with 15 mM trehalose and 0.1% CMC, not only recorded significantly highest cell count of consortium biofertilizer cultures, but also maximally supported multi-functional traits i.e., phosphate and zinc solubilization, ammonia and IAA production up to 150 days. Further evaluation of seedling emergence and growth of wheat (PBW 826) under axenic conditions recorded WB5 amended with 15 mM trehalose-based consortium bioformulation to exhibit maximum emergence and growth of wheat seedlings. This low-cost liquid formulation can be used for large-scale biofertilizer production as a cost-effective liquid biofertilizer production technology.

Novel route of tannic acid biotransformation and their effect on major biopolymer synthesis in Azotobacter sp. SSB81.

AIMS: To examine tannic acid (TA) utilization capacity by nitrogen-fixing bacteria, Azotobacter sp. SSB81, and identify the intermediate products during biotransformation. Another aim of this work is to investigate the effects of TA on major biopolymers like extracellular polysaccharide (EPS) and polyhydroxybutyrate (PHB) synthesis. METHODS AND RESULTS: Tannic acid utilization and tolerance capacity of the strain was determined according to CLSI method. Intermediate products were identified using high-performance liquid chromatography, LC-MS/MS and (1) H NMR analysis. Intermediates were quantified by multiple reactions monitoring using LC-MS/MS. The strain was able to tolerate a high level of TA and utilized through enzymatic system. Growth of Azotobacter in TA-supplemented medium was characterized by an extended lag phase and decreased growth rate. Presence of TA catalytic enzymes as tannase, polyphenol oxidase (PPO) and phenol decarboxylase was confirmed in cell lysate using their specific substrates. PPO activity was more prominent in TA-supplemented mineral medium after 48 h of growth when gallic to ellagic acid (EA) reversible reaction was remarkable. Phase contrast and scanning electron microscopic analysis revealed elongated and irregular size of Azotobacter cells in response to TA. (1) H NMR analysis indicated that TA was transformed into gallic acid (GA), EA and pyrogallol. Biopolymer (EPS and PHB) production was decreased several folds in the presence of TA compared with cells grown in only glucose medium. CONCLUSIONS: This is the first evidence on the biotransformation of TA by Azotobacter and also elevated level of EA production from gallotannins. Azotobacter has developed the mechanism to utilize TA for their carbon and energy source. SIGNIFICANCE AND IMPACT OF THE STUDY: The widespread occurrence and exploitation of Azotobacter sp. strain SSB81 in agricultural and forest soil have an additional advantage to utilize the soil-accumulated TA and detoxifies the allelopathic effect of constant accumulated TA in soil.

Effects of lindane on lindane-degrading Azotobacter chroococcum; evaluation of toxicity of possible degradation product(s) on plant and insect.

The effects of lindane on growth and plant growth-promoting traits of two lindane-degrading Azotobacter chroococcum strains (JL 15 and JL 104) were determined. The potential of both A. chroococcum strains to degrade lindane was also determined. Lower concentrations of lindane had a stimulatory effect, and higher concentrations generally had an inhibitory effect on growth and plant growth-promoting activities. A high percentage (>90%) of lindane was degraded by both strains at a lindane concentration of 10 ppm. Lindane at 1,000 ppm decreased seed germination and reduced seedling fresh weight. However, the possible degradation products for a starting lindane concentration of 10 ppm was found to be non-phytotoxic. Toxicity studies with larvae of Spilarctia obliqua resulted in an LC50 estimate of 3.41 ppm for lindane solutions into which leaf discs were dipped. No toxicity was observed for possible degradation products.

Association with an ammonium-excreting bacterium allows diazotrophic culture of oil-rich eukaryotic microalgae.

Concerns regarding the depletion of the world's reserves of oil and global climate change have promoted an intensification of research and development toward the production of biofuels and other alternative sources of energy during the last years. There is currently much interest in developing the technology for third-generation biofuels from microalgal biomass mainly because of its potential for high yields and reduced land use changes in comparison with biofuels derived from plant feedstocks. Regardless of the nature of the feedstock, the use of fertilizers, especially nitrogen, entails a potential economic and environmental drawback for the sustainability of biofuel production. In this work, we have studied the possibility of nitrogen biofertilization by diazotrophic bacteria applied to cultured microalgae as a promising feedstock for next-generation biofuels. We have obtained an Azotobacter vinelandii mutant strain that accumulates several times more ammonium in culture medium than wild-type cells. The ammonium excreted by the mutant cells is bioavailable to promote the growth of nondiazotrophic microalgae. Moreover, this synthetic symbiosis was able to produce an oil-rich microalgal biomass using both carbon and nitrogen from the air. This work provides a proof of concept that artificial symbiosis may be considered an alternative strategy for the low-N-intensive cultivation of microalgae for the sustainable production of next-generation biofuels and other bioproducts.

Integrated approach for disease management and growth enhancement of Sesamum indicum L. utilizing Azotobacter chroococcum TRA2 and chemical fertilizer.

Azotobacter chroococcum TRA2, an isolate of wheat rhizosphere displayed plant growth promoting attributes including indole acetic acid, HCN, siderophore production, solubilization of inorganic phosphate and fixation of atmospheric nitrogen. In addition, it showed strong antagonistic effect against Macrophomina phaseolina and Fusarium oxysporum. It also caused degradation and digestion of cell wall components, resulting in hyphal perforations, empty cell (halo) formation, shrinking and lysis of fungal mycelia along with significant degeneration of conidia. Fertilizer adaptive variant strain of A. chroococcum TRA2 was studied with Tn5 induced streptomycin resistant transconjugants of wild type tetracycline-resistant TRA2 (designated TRA2(tetra+strep+)) after different durations. The strain was significantly competent in rhizosphere, as its population increased by 15.29 % in rhizosphere of Sesamum indicum. Seed bacterization with the strain TRA2 resulted in significant increase in vegetative growth parameters and yield of sesame over the non-bacterized seeds. However, application of TRA2 with half dose of fertilizers showed sesame yield almost similar to that obtained by full dose treatment. Moreover, the oil yield increased by 24.20 %, while protein yield increased by 35.92 % in treatment receiving half dose of fertilizer along with TRA2 bacterized seeds, as compared to untreated control.

[Dynamics of diazotrophic bacteria number in the root zone of wheat Vrn lines isogenic by genes].

The number of diazotrophic bacteria and nitrogenase activity in the root zone of isogenic monogene-dominant Vrn lines were measured in the field experiments throughout their vegetation from tillering to heading. The total number of diazotrophic bacteria and nitrogenase activity in the root zone of these lines during this period were increased irrespective of their genotypes. The above indices of the winter cultivar (Vrn loci bottom recessive) were lower than those of the spring lines--Vrn-A1, Vrn-B1 and Vrn-D1. Plants of Vrn-B1 line have the lowest indices among the spring lines with the exception of some indices. This line plants flowered later than those of Vrn-A1 and Vrn-D1 lines. We hypothesized the differences between plants of these lines as to nitrogen fixation activity and the number of diazotrophic bacteria are mediately determined by Vrn loci through their effects on metabolism intensity and assimilate reflux in the form of root exudates, therefore the total number of diazotrophic bacteria and nitrogenase activity increases.

A new phenol oxidase produced during melanogenesis and encystment stage in the nitrogen-fixing soil bacterium Azotobacter chroococcum.

Laccases are copper-containing phenol oxidases that are commonly found in many types of plant, insect, fungi and bacteria. Whilst phenol oxidases have been well characterized in fungal species, laccase-type enzymes originating from bacteria have been much less well defined. Bacteria belonging to the family Azotobacteraceae share many morphological characteristics with strains already known to exhibit polyphenol and phenol oxidase activity; and hence the aim of this work was to identify and characterize a novel laccase from the isolated strain Azotobacter chroococcum SBUG 1484 in an attempt to provide further understanding of the roles such enzymes play in physiological development. Laccase activity was clearly observed through oxidation of 2,6-dimethoxyphenol, other typical substrates including: methoxy-monophenols, ortho- and para-diphenols, 4-hydroxyindole, and the non-phenolic compound para-phenylenediamine. A. chroococcum SBUG 1484 showed production of a cell-associated phenol oxidase when grown under nitrogen-fixing conditions, and was also observed when cells enter the melanogenic and encystment stages of growth. Catechol which is structurally related to melanin compounds was also released from Azotobacter cells into the surrounding culture medium during nitrogen-fixing growth. From our results we propose that a membrane-bound laccase plays an important role in the formation of melanin, which was monitored to correlate with progression of A. chroococcum SBUG 1484 cells into the encystment stage of growth.

Physiological studies on endorhizospheric establishment of Azotobacter chroococcum in wheat.

Ten strains of Azotobacter chroococcum were studied for their ability to invade the endorhizosphere of wheat. Strain W-5 exhibited ability to invade endorhizosphere as shown in the microscopic observations. This strain was compared with the strain OA-3 which did not invade the endorhizosphere zone. Strain W-5 showed higher production of cellulase and pectinase than OA-3. Both the strains induced defense enzymes in the host plant. However, induction of peroxidase and phenylalanine ammonia lyase activities (PAL) was higher in OA-3 than W-5. Quantitative differences in flavonoid like compounds obtained from root extracts and root exudates of plants inoculated with these strains were observed.

Biocontrol of Rhizoctonia solani (Kühn) and Fusarium solani (Marti) causing damping-off disease in tomato with Azotobacter chroococcum and Pseudomonas fluorescens.

BACKGROUND AND OBJECTIVE: The Damping-off disease is one of the most reasons for low productively of tomato in the world, especially in Iraq. In the current study, two types of bacteria (Azotobacter chroococcum and Pseudomonas fluorescens) were used to evaluate their efficacy in inhibiting the growth of pathogenic fungi Rhizoctonia solani and Fusarium solani and protecting the seeds of tomato and increasing their germination percentage. MATERIALS AND METHODS: Dual culture technique and Food poisoning technique were used to study the effect of bacteria on the growth of fungi understudy, and study the effect of bacterial filtrates on germination of tomato seeds. RESULTS: A. chroococcum showed the strongest antagonistic activity followed by P. fluorescens with the percentage of inhibition ranging between 72.9-77.1 and 69.5-70.3% for R. solani and F. solani respectively after 7 days of incubation. The effect of A. chroococcum and P. fluorescens filtrates were increased and also increased the inhibition of growth of fungi understudy, A. chroococcum filtrate also showed the strongest inhibitory effect followed by P. fluorescens with the percentage of inhibition ranging between 86.0-87.0 and 83.0-83.5% for R. solani and F. solani respectively at 20% concentration of filtrate. The percentage of seeds germination reached 90% in the treatment of A. chroococcum filtrate and 80% in the treatment of P. fluorescens filtrate. CONCLUSION: It can be concluded that the filtrates of A. chroococcum and P. fluorescens have antifungal properties against R. solani and F. solani and provided a high protection and increasing tomato seeds germination percentage.

Characterization of heavy metal toxicity in some plants and microorganisms-A preliminary approach for environmental bioremediation.

In situ bioremediation processes are important for control of pollution and clean-up of contaminated sites. The study and implementation of such processes can be designed through investigations on natural mechanisms of absorption, biotransformation, bioaccumulation and toxicity of pollutants in plants and microorganisms. Here, the phytotoxic effects of Cr(VI) and Cd(II) on seed germination and plant growth of Lepidium sativum have been examined at various concentrations (30-300 mg/L) in single ion solutions. The studies also addressed the ecotoxicity of metal ions on Azotobacter chroococcum and Pichia sp. isolated from soil. Microbial growth was estimated by weighing the dry biomass and determining the enzymatic activities of dehydrogenase and catalase. The results showed that Cr(VI) and Cd(II) can inhibit L. sativum seed germination and root development, depending on the metal ion and its concentration. The phytotoxic effect of heavy metals was also confirmed by the reduced amounts of dried biomass. Toxicity assays demonstrated the adverse effect of Cr(VI) and Cd(II) on growth of Azotobacter sp. and Pichia sp., manifested by a biomass decrease of more than 50 % at heavy metal concentrations of 150-300 mg/L. The results confirmed close links between phytotoxicity of metals and their bioavailability for phytoextraction. Studies on the bioremediation potential of soils contaminated with Cr(VI) and Cd(II) using microbial strains focusing on Azotobacter sp. and Pichia sp. showed that the microbes can only tolerate heavy metal stress at low concentrations. These investigations on plants and microorganisms revealed their ability to withstand metal toxicity and develop tolerance to heavy metals.

Azotobacter cysts: reactivation by white light after inactivation by ultraviolet radiation.

Cysts of Azotobacter vinelandii 12837 inactivated by ultraviolet radiation can be reactivated by white light. This photoreactivation mechanism is not seen in the vegetative cells of the same organism.

Microbial uptake of lead.

Micrococcus luteus and Azotobacter sp. cells grown in broth in contact with a dialysis membrane containing lead bromide were found to immobilize 4.9 and 3.1 x 10(2) milligrams of lead per gram of whole cells, on a dry weight basis, respectively. Culture turbidity and cell count measurements on these and other cell cultures show that lead bromide, lead iodide, and lead bromochloride in concentrations approaching solubility limits have no detectable effect on overall growth rate and cell viability. Analyses of cellular subfractions reveal that fractions of cell wall plus membrane contain 99.3 and 99.1 percent of the lead found associated with Micrococcus luteus and Azotobacter sp., respectively. The remainder is found associated with the cytoplasmic fractions.

Encystment of Azotobacter nigricans grown diazotrophically on kerosene as sole carbon source.

Encystment of Azotobacter nigricans was induced by its diazotrophic cultivation on kerosene. Its growth and nitrogenase activity were affected by kerosene in comparison to cultures grown on sucrose. Electron microscopy of vegetative cells showed that when nitrogenase activity was higher and the poly-beta-hydroxybutyrate granules were not present to a significant extent, peripheral bodies were abundant. After 8 days of culture on kerosene, the presence of cysts with intracellular bunches of poly-beta-hydroxybutyrate granules was observed. Germination of cysts bears germinating multicelled yet unbroken capsule cysts with up to three cells inside. This is the first report of encystment induction of Azotobacter species grown on kerosene.

Nitrogen fixation capacity of Azotobacter spp. strains isolated from soils in different ecosystems and relationship between them and the microbiological properties of soils.

The objectives of this study were to count and culture Azotobacter spp. in sampled soils, to determine the nitrogen (N) fixing capacity byAzotobacter spp. in pure culture and different soils, and to explore the relationships between N fixation capacity of Azotobacter spp. and microbiological properties of soils in Northern Anatolia, Turkey. Statistically significant relationships were found between the population of Azotobacter spp. in soils and microbial biomass C (Cmic), dehydrogenase (DHA), beta-glucosidase (GA), alkaline phosphatase (APA) and arylsulphatase (ASA) activities. However, relationships between the population of Azotobacter spp. and basal soil respiration (BSR), urease (UA) and catalase (CA) activities were insignificant. The N fixation capacities of native 3 day old Azotobacter chroococcum strains added to Ashby Media varied from 3.50 to 29.35 microg N ml(-1) on average 10.24. In addition, N fixation capacities of Azotobacter spp. strains inoculated with clayey soil, loam soil, and sandy clay loam soil during eight week incubation period were 4.78-15.91 microg N g(-1), 9.03-13.47 microg N g(-1) and 6.51-16.60 microg N g(-1), respectively. It was concluded that the most N fixation by Azotobacter spp. was in sandy clay loam soils.