Science Feature

India's modern cave man

K. S. Jayaraman

doi:10.1038/nindia.2017.1 Published online 9 January 2017

Microbial life inside a cave in Meghalaya

© Baskar, R. et al

Ramanathan Baskar spends much of his time in underground caves exploring miles and miles of rock layers and eerie mineral deposit formations.

It’s not the mystery or adventure of caves that drives Baskar, a professor of environmental science at Guru Jambheshwar University of Science and Technology in Hisar. He and his team camp in subterranean caves to identify microbes thriving in these "geologically isolated, always dark, nutrient-limited" environments.

They work in the fascinating, new discipline of ‘cave geomicrobiology’, collecting rock samples, extracting DNA from them and culturing microbes to investigate their roles.

“Cave geomicrobiology has the potential to provide invaluable information on subterranean microbial ecosystem processes including microbial-mineral interactions in caves,” Baskar says. "Such preserved microbial systems are also potentially useful tools in the search for life on other planets," he told Nature India.

Microbial life evolved on earth in an environment prior to photosynthesis when there was limited nitrogen and most organisms used minerals for energy. "Cave environments, therefore, offer the potential to study ancient evolutionary relationships, the use of alternative sources of energy, and systems developed by microbes for scavenging scarce nutrients in such environments," he says.

India has 1545 caves. However, not much geomicrobiological work has been done in them, except research by Baskar’s group. Presenting a list of microbes identified by the team at the just-concluded Indian Science Congress in Tirupati, Baskar said new caves continue to be discovered in India offering potentially unique geochemical environments worth exploring.

Baskar in a cave with a co-reasercher
According to Baskar, microbial ecosystems survive for thousands of years despite starved cave conditions, shielded from weathering. This confirms that they can indeed induce myriad energy conserving reactions. "Such processes in caves are evidenced by the discovery of deposits of oxidized iron-manganese (ferromanganese), calcium carbonate, and elemental sulphur."

Baskar says the practical applications of cave microbiology include preservation of historical monuments and sculptures (through the identification of microbial species that precipitate protective calcite coatings), and possible discovery of new antibiotics. Due to unique adaptations to starvation, these species also have the potential to carry out bioremediation. They have been found to degrade complex hazardous aromatic compounds, such as plasticizers.

Microbial metabolism under conditions of starvation and its active influence on geochemistry can be used to recognise biomarkers for subsurface life on other planetary bodies, he says. Cave geomicrobiology research offers practical applications in medicine, human health and industry, and possibly to find life elsewhere in the solar system. "Given its potential, it ought to be strongly supported as one of the new, revolutionary areas of knowledge at the boundary of geology and microbiology,” Baskar adds.