Bioprospecting of Halotolerant Marine Bacteria from the Kelambakkam and Marakkanam Salterns, India for Wastewater Treatment of Plant Growth Promotion

Microbial life can be found over a wide range of extreme conditions like high salinity, pH, temperature, pressure, light intensity, oxygen and nutrients. Halotolerant or halophilic microorganisms, are able to live in saline environments, offer potential applications in various fields of Biotechnology. The halotolerant or halophilic microorganisms are important for maintenance of soil condition and nutrient recycling in saline environment. The environment is ideally placed at the inter-phase between the terrestrial and marine environment and support a rich and diverse group of microorganisms. In this study, attempts were made to isolate the halotolerant marine bacteria and screen them for enzymes to be used for the decolorization of textile dyes and tannery effluent. A total of 192 halotolerant marine bacteria were isolated from Kelambakkam and Marakanam Salterns and named as AMETH101 to AMETH292. The isolated strains were tested for their growth at various salt concentrations such as 0M, 0.5M, 2.5M and 5M. All were found to grow well at 0.5M NaCl concentration. These organisms were studied for their ability to produce enzymes like lipase, tannase and protease. Among these strains, 107 have exhibited lipase activity, 41 strains exhibited tannase activity and 130 strains have exhibited protease activity. Totally 192 strains were tested for IAA production using qualitative assay and found that 41 strains showed positive activity and the remaining strains showed negative activity. For morphological characterization, KOH string test and catalase tests were performed. The results indicated that among the 192 strains, 138 strains were gram positive and remaining were gram negative strains while all the strains were positive for catalase test. This preliminary study has demonstrated that bioprospecting of halotolerant marine bacteria may yield potential microorganisms to be used in various environmental and biotechnological applications. Isolated halotolerant bacteria are very good producers of extracellular enzymes and IAA. These halotolerant bacteria with the combined ability of producing bioremediation enzymes and plant growth promoting hormones enhances the potential uses of them for the treatment and reuse of industrial effluents for the irrigation of ornamental plants.