Isolation, Biochemical Characterization and Antagonistic Study of Pseudomonas Fluorescens in Soil Collected from Different Locations in Kerala

Abstract

Plant Growth Promoting Rhizobacteria (PGPR) is bacteria that populates roots and enhance the growth by a variety of mechanisms. Generally, PGPR promote plant growth directly by either increasing nutrient acquisition for example nitrogen, phosphorus, potassium and essential minerals, or modulating plant hormone levels, or by indirectly decreasing the inhibitory effects of pathogens on plant growth and development as biocontrol agents. In this study, an attempt was made to collect rhizospheric soil samples with native Pseudomonas population from different locations of Kerala state and to identify the native Pseudomonas fluorescens strains, a potent biocontrol agent in controlling pest, insects, nematodes and various pathogenic microbes as well as PGPR in the rhizosphere under UV light and further characterize them morphologically and culturally. Utmost P. fluorescens strains showed positive PGPR exertion. The study showed that Pseudomonas is an effective factory growth promoting bacterium. In the present study, soil samples were collected from different locales in Kerala (Trivandrum, Kollam and Kottayam) in order to insulate the soil microbes and also checking its negative parcels with other microbes. The observed colonies were identified as Pseudomonas fluorescens by checking the green fluorescence emitted by the colonies when exposed to UV light. These fluorescent colonies were selected and confirmed as Pseudomonas fluorescens using biochemical tests like MR test, Citrate utilisation test and Catalase test. The Methyl red (MR) test was used to identify the glucose utilizing property of Pseudomonas fluorescens. A change from yellow to cherry red colour indicates positive result. The Citrate Utilisation test was used to identify the ability of Pseudomonas fluorescens to utilize citrate as its sole carbon and energy source thereby confirming that the isolated colony is of the particular species. Catalase test was used to identify the ability of catalase containing Pseudomonas fluorescens to convert Hydrogen peroxide into Water and Oxygen. Presence of thick effervescence was noted confirming the catalase utilising ability of Pseudomonas fluorescens. Coagulase test is used in order to differentiate Staphylococcus aureus that is positive which produce the enzyme coagulase, from S. epidermis and S. saprophyticus negative one which do not produce coagulase.