Biogenic Evidences of Moonmilk Deposition in the Mawmluh Cave, Meghalaya, India

Abstract

Moonmilk, a microcrystalline secondary cave deposit, actively forms on the floor of Krem Mawmluh – a limestone cave in Meghalaya, Northeastern India. Due to the abundance of micrite and calcified microbial filaments, we hypothesize that these deposits form as a result of ongoing microbial interactions. Consistent with this idea, we report electron microscopic and microbiological evidences for the biological origin of moonmilk in Krem Mawmluh. Scanning electron microscopy indicated abundant calcified microbial filaments, needle calcite, fibre calcites (micro-fibre and nano-fibre calcite crystals), biofilm and microbial filaments in the moonmilk. The total viable culturable microbes showed high population densities for microbes in the moonmilk and moonmilk pool waters. In vitro culture experiments, confirmed the capability of many of the isolated strains to precipitate calcite and some of the identified isolates belonged to the Bacillus sp. and Actinomycetes. These results clearly support the biogenic nature of the deposits.