Microbial communities and volatile profiles heterogeneity in a Mars-analogue volcanic lake.

Analyses of the Martian surface suggest the existence of sedimentary lacustrine deposits that may have once harboured life. Lake Bagno dell'Acqua (Pantelleria, Italy) represents an optimal planetary field analogue for investigating the evolution and adaptation of life in Mars-like environments and for validating potential life-detection strategies. Accordingly, we characterised microbial communities and volatile organic compound profiles in actively growing organosedimentary structures within lake sediments and in biofilm covering hot springs at the lake margins. The microbial communities exhibited low taxonomic diversity and were dominated by a few extremophilic and extremotolerant taxa. Only a marginal difference in community composition was detected between sediment and biofilm samples; however, high variability was reported among the sampling sites and the replicates of each site. An exploratory volatile compound profiling revealed the presence of numerous terpenes, with small variability among sampling sites. The specialized assemblages detected in the Bagno dell'Acqua environment indicate that similar consortia could have adapted to analogous settings on ancient Mars. Patterns identified in these communities may serve as biosignatures, including redox imbalances generated by organisms driving oxidation-reduction processes. Moreover, pronounced fine-scale heterogeneity provides valuable insights into life-detection strategies in comparable extraterrestrial environments. The abundance of terpenes, ancient, widely distributed biomolecules across all domains of life, indicates that similar molecular adaptations may likewise have arisen in similar environments elsewhere. If preserved, these volatiles could represent promising biosignatures in clay-rich lacustrine sediments, such as those that were widespread on Noachian Mars and are abundant in the sediments of Lake Bagno dell'Acqua.