Microbial diversity of speleothems in two southeast Australian limestone cave arches

摘要

Peculiar cave structures, nicknamed lobsters, and shaped by drip water, wind, aeolian particles and microbial biofilms,are described from cave entrance arches at Jenolan and Wombeyan caves in southeast Australia. Subaerial biofilmson rock surfaces support complex microbial assemblages adapted to temperature, desiccation, and low irradiancestress. The community composition of active and inactive speleothems was elucidated by next generation sequencing.Active biofilms showed high abundances of cyanobacterial taxa, morphologically and phylogenetically belonging tothe genera Chroococcidiopsis and Gloeocapsa, representing an endolithic lifestyle in desiccated and low light conditions.Significant differences were found between caves and between actively accreting and inactive and weatheredstructures. Functional taxa putatively occupying the same niches were found on active structures in both locations. Atemporal succession is proposed, with dominance shifting from Chroococcales to Actinomycetales and highly desiccation-resistant and oligotrophic Rubrobacterales with decreasing water availability.