Microbial Activity in Subterranean Ecosystems: Recent Advances

Abstract

Of the several critical challenges present in environmental microbiology today, one is the assessment of the contribution of microorganisms in the carbon cycle in the Earth-climate system. Karstic subterranean ecosystems have been overlooked until recently. Covering up to 25% of the land surface and acting as a rapid CH4 sink and alternately as a CO2 source or sink, karstic subterranean ecosystems play a decisive role in the carbon cycle in terms of their contribution to the global balance of greenhouse gases. Recent data indicate that microbiota must play a significant ecological role in the biogeochemical processes that control the composition of the subterranean atmosphere, as well as in the availability of nutrients for the ecosystem. Nevertheless, there are still essential gaps in our knowledge concerning the budgets of greenhouse gases at the ecosystem scale and the possible feedback mechanisms between environmental-microclimatic conditions and the rates and type of activity of microbial communities in subterranean ecosystems. Another challenge is searching for bioactive compounds (antibiotics) used for treating human diseases. At present, there is a global health emergency and a strong need for novel biomolecules. In recent decades, great research efforts have been made to extract antibiotics from marine organisms. More recently, caves have been receiving considerable attention in search of novel antibiotics. Cave methanotrophic and heterotrophic bacteria are producers of bioactive compounds and may be potential sources of metabolites with antibacterial, antifungal or anticancer activities of interest in pharmacological and medical research, as well as enzymes with a further biotechnological use. Here we also show that bacteria isolated from mines, a still unexplored niche for scientists in search of novel compounds, can be a source of novel secondary metabolites.

Actinomycetes from Caves: An Overview of Their Diversity, Biotechnological Properties, and Insights for Their Use in Soil Environments

“…Several actinobacteria are responsible for a wide range of bioactive compound productions, such as enzyme inhibitors, immune modifiers, plant growth-promoting substances, and natural dyes, and they exert several antimicrobial, antifungal, anticancer, antiparasitic, and immunosuppressant activities [1,18,[39][40][41][42]. So far, studies and reviews have been mainly based on applying these compounds against human pathogens [18,43]. These studies report a broad spectrum of effectiveness against Gram-positive (e.g., Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (e.g., Pseudomonas aerungiosa), and fungi (e.g., Candida albicans) [30].…”

Metabolites of Marine Sediment-Derived Fungi: Actual Trends of Biological Activity Studies

“…The xanthone derivatives coniochaetone J (4) and epiremisporine B (5) from Penicillium sp. SCSIO Ind16F01 (the Indian Ocean) exhibited weak activity against enterovirus EV71 in vitro, and 5 also was active against influenza A virus subtype H3N2.…”

“…Bacteria produce antifungal metabolites to regulate the number of fungi in communities [ 5 ]. In turn, fungi release antibacterial compounds in an environment.…”

Advances in Industrial and Environmental Microbiology

“…Recent advances in understanding of the role of microbial communities in subterranean ecosystems, namely their contribution to biogeochemical processes affecting the composition of the subterranean atmosphere and the availability of nutrients is reviewed by Martin-Pozas et al [6]. These bacterial communities have been found to actively contribute to the uptake-fixation-production of CO 2 , CH 4 , and NxOx gases.…”