-By Kranti Karande
Sambhar Lake, located in the Rajasthan district, is the largest inland salt lake in India. It is a Ramsar site, a saline wetland of international importance because of the spectacular diversity of birds it attracts. The salt production from the lake is approximately 0.2 million tons per annum. Apart from this it is also considered as a hypersaline ecosystem because of high salinity which provides a great opportunity for microbial ecologists to understand halophiles. Over the last many years there are very few reports on the microbial diversity of halophiles, in particular archaea from Sambhar Lake.
Dr. Avinash Sharma’s group at NCMR-NCCS Pune cultivated diverse group of bacteria and archaea from Sambhar Lake. Archaea are very difficult to culture and not many research groups are working on this domain of life. Looking at the percentage of description of novel taxa belonging to bacteria and archaea, one can easily make out how poorly archaea are being studied. 13 genera were identified as archaeal while 12 genera belonging to bacteria were isolated in the current study. The authors also claim that there are 13 novel strains of archaea and bacteria isolated during study based on 16S rRNA gene sequencing and currently the group is working on genome analysis which is mandatory for the description of a novel taxa.
The reason behind capturing such a vast diversity was because of the multiple cultivation approaches used in the study. The cultivation of microorganisms was done using two used approaches: onsite enrichment and sediment dilution in the laboratory. In the first method of cultivation, soil samples were inoculated in different growth media onsite. The same media and salt concentrations were also used for isolation in the second approach. That is same growth conditions were used in both approaches. Interestingly besides common found genera in both cultivation methods: Alteribacillus, Halobacillus, Halorubrum, Lentibacillus, Natronorubrum,
Piscibacillus and Thalassobacillus were found only in onsite cultivation whereas only three genera Aliidiomarina, Natrinema and Natronolimnobius were found in laboratory processing.
Dr. Avinash Sharma said “Although both the approaches used for isolation are classical, but they provide better understanding to device sampling strategies. From our results we can conclude that it is important to use multiple cultivation approaches as these approaches help capturing vast group of organisms. Imagine if we would not have done the onsite enrichment we would have lost majority of the organisms we isolated in this study. We have also observed in the study how delay in sample processing effect the cell viability, although it is not possible to isolate each and every organism residing in the ecosystem but immediate sample processing is recommended to isolate majority of the organisms before they lose their viability”.
The microorganisms isolated in this study are known for the production of bio technologically important compounds like halocines, bacteriorhodopsins, exopolymer, hydrolytic enzymes and possessing the anti-proliferative, anti-oxidant and anti-hemolytic activity.
Conservation of such unique organisms at NCMR-NCCS enrich the culture collection and provide better resources for future studies/research.