USE OF THE MODIFIED WINOGRADSKY MICROCOSM TECHNIQUE TO HELP IN BUILDING AN INDIGENOUS CULTURE COLLECTION OF IRON AND SULPHUR BACTERIA VALUABLE IN GREEN SYNTHESIS OF GOLD NANOPARTICLESDabolkar Sujata and Kamat Nandkumar
This paper describes an easy to use modified winogradsky microcosm (MWMC) technique for enrichment and isolation of useful chemolithotrophic bacteria which are increasingly employed in green synthesis of Gold nanoparticles. The technique was necessitated due to non availability of pure cultures of Iron and Sulphur bacteria in India and find out a way to help the scientists to build an indigenous culture collection of such useful chemolithotrophic bacteria. Winogradsky column is an example of an interdependent microbial ecosystem and is an excellent tool to determine the major bacterial communities in a sample. Winogradsky columns have been used extensively to demonstrate microbial nutrient cycling and metabolic diversity. This work was aimed at application of the Winogradsky Microcosm (WGMC) by modification using simple, low cost PET bottles to enrich microbial biofilms of Iron and Sulphur bacteria from different local mineral samples in order to isolate useful cultures of particularly Acidithiobacillus, Leptospirillum and Sulfobacillus spp. After prolonged incubation in dark followed by exposure to light, interesting coloured zones were identified in 24 columns from six samples indicating differential colonization of biofilms of Iron and Sulphur bacteria. The biofilms were carefully sampled, microscopically analysed, aseptically processed, enriched and pure cultures of iron and sulphur bacteria were successfully obtained on specific hyperacidic media. These cultures have excellent potential in bioleaching of gold sulphides and green synthesis of pure Gold nanoparticles. Considering the dependence of our country on foreign nations to acquire such rare, expensive and patented cultures, our technique is claimed to be potentially helpful to Indian researchers to build an indigenous collection of industrially useful, diverse and chemically creative strains of Iron and Sulphur bacteria. The results are presented and discussed.