Studies on Characterization of Microorganisms for Solubilization of Phosphate, Potassium and Zinc

Abstract

Soil is the basis of life and we living beings are directly and indirectly depend on it. Agriculture is based fully on the soil because without it agriculture cannot sustain, it is the building block of agriculture. Soil have several organic, inorganic materials in it. Nutrients are one of the important part of soil because plants are directly influenced by the availability of nutrients. Deficiency of these nutrients causes severe damage to growth and yield of plants and crops. These are the basic need of plants and major nutrients include Phosphorous, Nitrogen, and Potassium. Rhizospheric soil samples were collected from native crop fields and nearby regions. Potential microbes were isolated and tested for solubilization of P, K and Zn on Pikovskayas medium, Aleksandrov’s agar medium and on Zinc solubilizing agar medium that were supplemented with P, K and Zn source. Mineral solubilization involves releasing of these bound nutrients by soil microorganism and making them available for plant uptake via three possible mechanisms that are acidification of the medium, production of chelating metabolites, and redox activity.The nutrient solubilizing bacteria generates a halo zone around their colony on the basis of which their solubilization potential was identified.A total of 18 isolates, two isolated from soil and 16 from previous studies, were tested for multiple solubilization potential, some were found to solubilize all the three nutrients.Microscopic studies showed presence of bacteria with rods, oval, and cocci cell morphology. 17 isolates were gram negative and one Gram positive. Colony morphology showed05 isolates were greenish-yellow fluorescence producing bacteria denoted as MS-1, PYS-2, PYS-3, PYS-11, PYS-14 and S6 producing yellowish green fluorescence,02 isolates S4 and MS-3 were brown pigment producing gram negative rods.IsolateSS-9-2 was gram positive with cocci or in some instance streptococci cell arrangement. During plate assay for solubilization,isolates S4, S6, MS-1, PYS-14 and SS-9-2 showed highest level of solubilization of P present in the form of tricalcium phosphate. Isolates S1, S6, MS-1, MS-3, SS-7-6, SS-7-7and SS-9-2 showed potential to solubilize K present in the form of potassium aluminosilicate. Whereas Zn present as zinc oxide in media was solubilized by S1, S6, MS-3, PYS-2, PYS-11, PYS-14, SS 7-6 and SS-9-2. The study showed that isolates S1, S6, MS-1, PYS-2, PYS-3, PYS-11, PYS-14 and SS-9-2 can solubilize either of the nutrient (P, K and Zn), an, two or all the three efficiently.On the basis of above study 09 potential isolates (S1, S4, S6, MS-1, MS-3, PYS-2, SS-7-6, SS-7-7 and SS-9-2) were selected to perform biochemical tests for their diversity analysis. 13 biochemical tests were performed to identify isolates. Isolates showed different characteristics in terms of morphology, solubilization assay and biochemical tests but some on the other hand showed similarities in either of the aspect making them relating to same genera. The results indicated that isolates differ in their ability and potential to solubilize multiple nutrients, it was also imperative that many isolates were showing higher solubilization of one specific nutrient only, some of the isolates were poor solubilizers of two or in some instance all three nutrients. These isolates however may serve as reference stocks for further studies on nutrient solubilization assay and its mechanisms.