Karst subterranean cave sediments are vulnerable ecosystems, hosting microbial communities that provide crucial services, such as nutrient cycling and pollutant degradation.
So far, these systems have not been studied adequately at the microbial functional level, yet, they currently contribute around 25% of the world’s drinking water. Rather than passive deposits, cave sediments are dynamic microbial habitats that influence fundamental biogeochemical processes through nitrogen, sulfur, and carbon cycling.
A new study on cave microbiology addresses this gap, co-authored by LifeWatch Slovenia member Janez Mulec (Karst Research Institute – ZRC SAZU), together with Lejla Pašić (Sarajevo Medical School) and Andreea Oarga-Mulec (Materials Research Laboratory).
The paper, recently published in Frontiers in Microbiology, highlights how cave-sediment bacteria in the the Slovenian eLTER Postojna-Planina Cave System site respond to environmental change, examining key environmental factors such as sediment age and short-term environmental variability.
Slovenian researchers are trying to understand whether these factors have any influence on substrate degradation, taxonomic composition, and on the metabolic potential of bacterial communities. In the midst of hydroclimatic extremes such as floods, droughts, and rising cave temperatures, it is fundamental to understand if these communities are capable of adapting to climate change.
The paper examines two types of sediments that host these microbial habitats: alluvial sediments recently deposited (surface), subject to hydrological and geochemical variability, and ancient palaeo-river deposit (subsurface), the latter still under-investigated in comparison to the first type, despite its potential to tell us a lot more about microbial ecological functions.
The authors have shown that older sediments can actually function as a geochemical filter: the palaeo-deposit exhibited low taxonomic and functional diversity alongside elevated heavy metal concentrations, consistent with constraints on microbial functioning under long-term geochemical stress. Adaptive traits have been revealed in key taxa, such as Polaromonas, Methylibium, and Beggiatoa.
The study integrates functional and taxonomic approaches, using metagenomic analysis, community-level physiological profiling (CLPP), and sediment geochemistry to assess the roles of sediment age, oxygen availability and temperature, as well as the potential of the microbial communities for applied environmental use.
Read the full article: (DOI: 10.3389/fmicb.2025.1724116).










