ROLE OF MICROBES IN COLORING AND STABILIZATION OF THE SANDSTONE OUTCROPS IN COLORADO PLATEAU, USA

Arid lands cover about one third of the global land surface and thirty percent of the land area of United States. Our study is focused on sandstone outcrops of the Grand Staircase-Escalante National Monument (GSENM) in southern Utah, USA. Despite the harsh environmental conditions in deserts, microorganisms are able to colonize the pore spaces of these rocks forming subsurface microbial mats. The survival mechanism deployed by these microbes is the production of extracellular polymeric substances (EPS) forming a slimy matrix that retains water and regulates temperature fluctuations. The major inhabitants of these microbial mats are Cyanobacteria along with Proteobacteria as revealed by Miseq Illumina sequencing analysis. Studies in our lab revealed that these microbial communities are involved in the hardening of the surface of sandstone outcrops. An interesting phenomenon known as “Iron-bleaching” was observed in these sandstone outcrops due to the removal of iron (III) from the hematite cladding of the sand grains within the stone, resulting in the lightening of the stone. Data from our laboratory suggests that this is an ongoing process wherein ferrous iron is entrapped by the EPS produced by these microbial communities. Biochemical analysis of the EPS revealed that it is majorly composed of polysaccharides, mainly uronic acids. Competitive binding experiments suggested that EPS has a potential role in binding other metal cations such as cobalt and further studies are in progress to understand these micro scale metal interactions with microbial life in this ecosystem. Based on the above findings, we hypothesize that EPS acts like a bio filter concentrating nutrients and metal cations essential for the survival of microbial life in the sandstones. Therefore, these microbial communities potentially play an integral role in the cycling of elements at a micro scale level in this ecosystem.