A. Fallah Nosrat Abad; M. Habibi
Abstract
Introduction: According to WHO and FAO studies, the diseases caused by contaminated foods are of the most widespread threats to human health in developing and developed countries. Therefore, in recent years, researchers have been trying to use soil microorganisms to solve this problem and maintain the ...
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Introduction: According to WHO and FAO studies, the diseases caused by contaminated foods are of the most widespread threats to human health in developing and developed countries. Therefore, in recent years, researchers have been trying to use soil microorganisms to solve this problem and maintain the health of plants and the environment. Phosphorus after nitrogen, is a major macronutrient in plants which controls the growth, seeding and fruit production and involves in basic biological functions such as cell division, nucleic acids synthesis, photosynthesis and respiration and energy transfer. However, high amount of soluble inorganic phosphate is annually applied to the soil as chemical fertilizer but a large portion of it is immobilized rapidly after application due to phosphate fixation by aluminum, calcium, iron, magnesium and soil colloids and becomes unavailable to plants. The use of biological agents especially phosphate solubilizing microorganisms, can play an important role in supplying plant nutrients and improves crop health and productivity without causing any harm in agricultural and natural ecosystems. Bacteria and fungi are the two important groups of phosphate solubilizing microorganisms. Phosphate solubilizing bacteria in soil include Rhizobium, Bacillus, Pseudomonas, Agrobacterium, Achromobacter, Enterobacter and Burkholderia, and the most important ones i.e., Bacillus sp. and Pseudomonas flourescens. Material and Methods: In order to evaluate the effect of Thiobacillus, sulfur and phosphorus applicationon population of phosphate solubilizing bacteria in soil, a field experiment was conducted at Zarghan Agricultural and Natural Resources Research Center of Iran in a factorial, based on complete randomized block design with 3 replications. Treatments consisted of three levels of sulfur fertilizer with biofertilizer containing Thiobacillus bacteria (without sulfur and biofertilizer containing Thiobacillus (S0), application of 500 kg S + 10 kg biofertilizer containing Thiobacillus (S1), 1000 kg S + 20 kg biofertilizer containing Thiobacillus (S2) and 2000 kg S + 40 kg biofertilizer containing Thiobacillus (S3) per hectare), three levels of triple super phosphate (without phosphorus (P0), 100% (P1) and 65% (P2) percent phosphorus recommended based on the soil test) in two corn planted and not planted states. After harvesting, 72 soil samples were collected from each plot and transferred to the biology laboratory of soil and water research institute of Karaj. Soil samples were stored in sterile conditions at 4◦C. In order to isolate phosphate solubilizing bacteria, 10 gram of soil from each sample was suspended in 90 ml of sterilized water to make 1:10 dilution. Then, series of dilution were made (101 – 107) and 0.1 ml of suspensions of the diluted soil sample were transferred to petri dishes containing pikovskaya medium and incubated at 28- 30˚C. To identify PSP from halos surrounding characterized colonies was used and counting was performed 1-14 days after cultivation. The colonies were isolated on the basis morphological characteristics such as shape, color and size and then purified by linear culture. Finally, 60 strains were purified that were used to compare phosphate solubilizing capability. Results and Discussion: The results of this study showed that the main and interaction effects of sulfur fertilizer and biofertilizer treatments of Thiobacillus, phosphorus and plants on the population of phosphate-solubilizing bacteria (cells per gram of dry soil) in Pikovskaya medium were significant at 0.01 level probability. The highest population of bacteria was obtained at the lowest level (S1). Increasing the level of sulfur fertilizer and Thiobacillus biofertilizer decreased the population of phosphate-solubilizing bacteria and the highest level of sulfur and Thiobacillus biofertilizer led to the lowest bacterial population. Also, the study of phosphorus application on the bacterial population showed that phosphorus fertilizer at both levels significantly increased the bacterial population compared to the control (no application phosphorus). The best fertilizer treatment for phosphorus application was P1 which had the greatest effect on bacterial population compared to P2 treatment in Pikovskaya environment. In this experiment, the population of bacteria in corn planted conditions was higher than in non-planted conditions and this population increase was observed in almost all different levels of sulfur and phosphorus fertilizers. The highest bacterial population was observed in combined treatment of S1P2 under corn planted conditions. The results of microscopic, physiological and biochemical tests of the strains showed that all 60 bacterial strains were capable to form clear zone in Pikovskaya medium. Among them, 15 strains (7, 3, 2 and 3 strains belonging to Bacillus megaterium, Bacillus subtilis, Bacillus cereus and Pseudomonas fluorescent, respectively) had higher phosphate solubility than the others.
M. Hassanshahian; S. Ghorbani
Abstract
Introduction: One of the most important indicators in relation to industry, economy and environment is to achieve the most recovery with the least cost and minimum pollution. Today, the use of chemolithotrophic microorganisms is common for extraction of some metals such as cooper, uranium, gold, cobalt ...
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Introduction: One of the most important indicators in relation to industry, economy and environment is to achieve the most recovery with the least cost and minimum pollution. Today, the use of chemolithotrophic microorganisms is common for extraction of some metals such as cooper, uranium, gold, cobalt and molybdenum in bioleaching process of low-grade rocks. Attention to the bioleaching of heavy metals such as copper, nickel, cobalt, zinc, and molybdenum has been increased in recent years because of its application to low-grade ores. The variety of microbes identified as being capable of growth in situations that simulate bio-mining commercial processes is rapidly growing. This is partly because of an increase in the number of environments being screened for such organisms, partly because of an increase in the variety of minerals being tested, and most importantly because of new techniques available to screen for the presence of organisms. The aim of the present research was to study the quantity of two important autotrophic bacteria, iron and sulfur oxidizing bacteria, in different regions of Miduk mine in Shahrbabak, Kerman province.
Materials and Methods The soil samples were collected from different locations of Miduk cooper mine such as: Sulfuric Pool Acid Discharge (PAD), Oxidic PAD, Sulfuric damp, Pool Leaching Sulfuric (PLS)and leaching hip. Top layer of mine soil (about 1 cm) was removed. In each site, soil samples were collected from five different spots. The quantity of iron and sulfur oxidizing bacteria were measured by culture of serial dilutions of samples in 9K medium with Iron and sulfur as electron sources, respectively. The 9K medium was used for enrichment of iron and sulfur oxidizing bacteria in collected mine samples. These two important groups of bacteria have autotrophic growth but the energy sources for these two bacteria are different. Iron oxidizing bacteria use ferrous ion in form of FeSO4 but sulfur oxidizing bacteria use inorganic sulfur and sulfur compounds as a source of energy and obtain the carbon from the reduction of the CO2 of the atmosphere, in autotrophic growth. Heterotrophic bacteria were quantified by culture in nutrient broth medium. Most probable number (MPN) method was used to enumeration the autotrophic and heterotrophic bacteria by culture of samples in 24 well microplates with specific medium. The positive index for enumeration iron and sulfur oxidizing bacteria in these experiments were red color and turbidity, respectively. The microplates were incubated for 21 days for autotrophic bacteria and 7 days for heterotrophic bacteria.
Results and Discussion: The results of this research showed that the highest quantity of heterotrophic bacteria related to soil near to PLS and the lowest quantity belonged to sulfuric PAD. Iron oxidizing bacteria had the highest density on oxidizing Pad (OP) and the lowest density of these bacteria found in soil near to PLS. The diversity of iron oxidizing bacteria was low in the mine. The lowest quantity of sulfur oxidizing bacteria related to oxidizing PAD. Although appropriate diversity of sulfur oxidizing bacteria in compare to iron oxidizing bacteria was observed in the Miduk mine. These results about quantity of iron oxidizing bacteria confirmed this truth that the presence of oxygen and also low acidity in oxidizing Pad (OP) has major effect on the distribution and quantity of iron oxidizing bacteria. Because, the optimum condition for growth of iron oxidizing bacteria is low acidity and abundance of oxygen that these two factors provided in oxidic Pad (OP).
The quantity of sulfur oxidizing bacteria was high in yellow soil near to PLS. These results obtained by enumeration with MPN and Newbar lam methods. This result can be interpreted as the high concentration of sulfur element in this region has a selection force to prevalent the sulfur oxidizing bacteria in compare to iron oxidizing bacteria in this region. Because, when the sulfur is high, the bacteria that can use this element as their only energy source for fixation of CO2 is dramatically increased.
Conclusions: In the present research, the quantity and distribution of iron and sulfur oxidizing bacteria of Miduk cooper mine were studied. Based on the results, iron and sulfur oxidizing bacteria had the highest density on oxidizing Pad (OP) and in yellow soil near to PLS, respectively. Although sulfur oxidizing bacteria had an appropriate diversity compared to iron oxidizing bacteria in Miduk mine. However, the results obtained in this study confirmed that the sufficient quantity of iron and sulfur oxidizing bacteria were present in this mine. Then, the soil bacteria of this mine can be used to enhance the bioleaching process in Miduk mine.
A. Gholami; A. Ansouri; H. Abbas dokht; A. Fallah Nosrat Abad
Abstract
Introduction: Sulfur is the key element for higher crops and plays an important role in the formation of proteins, vitamins, and enzymes. It is a constituent of amino acids such as cysteine and methionine, which act for the synthesis of other compounds containing reduced sulfur, such as chlorophyll and ...
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Introduction: Sulfur is the key element for higher crops and plays an important role in the formation of proteins, vitamins, and enzymes. It is a constituent of amino acids such as cysteine and methionine, which act for the synthesis of other compounds containing reduced sulfur, such as chlorophyll and utilization of phosphorus and otheressential nutrients.Deficiency of this nutrient in soil is usually compensated by using chemical fertilizers. However, these fertilizers have harmful effects on the environment and decrease the quality of the agriculture products. Therefore, biological fertilizers are more useful for using in agricultural ecosystems.Sulfurshould be addedto the soil, usually in a reduced form such as elemental sulfur. Use of S oxidizers enhances the rate of natural oxidation of S and speeds up the production of sulfates and makes them available to plants consequently resulting in an increased plant yield. The role of chemolithotrophic bacteria of the genus Thiobacillus through oxidation process in the soil is usually emphasized. Sulfur oxidation is the most important step of sulfur cycle, which improves soil fertility. The result is formation of sulfate, which can be used by the plants, while the acidity produced by oxidation helps to solubilize nutrients in alkaline soils. These bacteria can solubilise the soil minerals through the production of H2SO4 that reacts with these non-soluble minerals and oxidised them to be available nutrients to the cultivated plants. Arbuscular MycorrhizalFungi isan important component ofthe microbiota, mutualistic symbioticsoilfungithatcolonizesthe rootsofmost cropplants.The AM symbiosis involves an about 80% of land plant species and 92% of plant families. They have theability to enhance host uptake of relativelyimmobile nutrientsparticularly phosphorus (P) andzinc (Zn),Manganese (Mn) andiron(Fe).Arbuscular mycorrhizal fungi increased plant uptake of phosphorus, nitrogen and water absorption. Inoculation withthesefungihas increased the yield of numerous field-grown crops.
This study was aimed to evaluate the effects of thiobacillus bacteria and sulfur application on soil pH, and also their interactions with mycorrhizal fungi in order to improve nutrients uptake and grain yield of maize under alkaline soil condition.
Materials and Methods: Treatments arranged as factorial experiment were based on RCBD with three replications. Treatments consisted of mycorrhizal inoculation: inoculated (m1) and non-inoculated (m0), thiobacillus in two levels of inoculated (t1) and non-inoculated (t0) and three levels of sulfur (S0: 0 kg.ha-1, S1: 250 kg.ha-1 and S2: 500 kg.ha-1). Four-row plots were prepared with row width and intra-row space of 60 and 20 cm, respectively. Seeds of maize (Zea Mays, Sc:647) were surface sterilized in a 10% (v/v) solution of hydrogen peroxide for 10 min, were rinsed with sterile distilled water. Before sowing, 300 kg of urea per hectare were applied according to the results of soil analysis. In order to facilitate oxidation of sulfur to sulfate form, , S was applied and thoroughly mixed into top 30 cm of soil 30 days before sowing. One week before sowing, thiobacillus (Thiobacillus thiooxidans) was inoculated. Inoculum of AM fungus Glomus intraradices, were added to soil just before planting at about 2 centimeters below seed sowing dept. To measure Arbuscular Mycorrhizal colonization, root plants collected one week before harvesting, cleared in 10% KOH at 80˚C for 2 h, and then acidified in 1% HCL for 60 min. Then the cleared roots were stained in a solution of Trypan blue. For nutrient analysis, the following procedure was applied. Zn, Fe, S, and P were determined by Inductively Coupled Plasma-atomic emission spectrometry apparatus. For this purpose, ash of seed samples was prepared at 500-550 degree of Celsius and then 5 ml of HCl 37% was added and with dionized water to reach to 50 ml. Kjeldahl method was used to determine nitrogen. Analysis of variance was performed on all experimental data and means were compared using the least Significant Differences (LSD) test with SAS software. The significance level was p>0.05 unless stated otherwise.
Results and Discussion: Results showed sulfur application increased significantly the amount of S, P, N, Fe, Zn, shoot dry weight and leaf chlorophyll of maize. With increasing Sulfur, sulfur concentration in plant shoot increased with linear trend. The highest S concentration was obtained with 200 mg.kg-1 S and the lowest amount was obtained from control plots. Applications of 50, 100, 150 and 200 mg.kg-1 S increased P content about 0.45, 3.91, 4.74 and 5.56 %, respectively. The highest N contentwas obtained with 100 mg.kg-1 S. The thiobacillus significantly increased P, Fe, Zn anddecreased root colonization and soil pH compared to control. Thiobacillus bacteria increased shoot P only with application of 100 mg.kg-1 S. Mycorrhizal inoculation increased the amount of N, P, S, Fe, Zn, shoot dry weight and root colonization. Inoculation with G.intra and G.mosseae increased shoot P content about 4.18 and 3.34% in comparison with the control plots. Single or combination of sulfur and thiobacillus had a negative impact on the root colonization. Based on the results it seems that sulfur, thiobacillus and mycorrhiza in alkaline soils improved crops nutrition and growth. S application and thiobacillus interaction on S concentration of maize shoot were significant. In condition of 0 or 50 mg.kg-1 S application, inoculation of thiobacillus is recommended. Also, the effects of mycorrhiza on P shoot was significant with no application of S.
