Abstract EANA2026-44

Microbial habitability is fundamentally constrained by the availability of nutrients and free energy gradients. In such context, metabolic cooperation within communities enables the exploitation of otherwise inaccessible ecological niches. Stratified ecosystems such as Winogradsky columns provide powerful laboratory analogues to investigate how microbial interactions across redox gradients drive biogeochemically relevant processes and shape detectable biosignatures. Here, we use Winogradsky columns inoculated with biofilms from a sulfur-rich terrestrial environment to study microbial communities structured by tightly coupled sulfur, carbon, and oxygen cycles. Over five months of incubation, the columns developed distinct coloured layers corresponding to spatially organized metabolic guilds, including oxygenic phototrophs (cyanobacteria) and anoxygenic phototrophs (green/purple sulfur bacteria). To explore how those microorganisms differing in metabolic activity also differ in biosignature expression, we measured the fractional circular polarization of light using FlyPol, a highly sensitive spectropolarimeter capable of detecting molecular homochirality, a key feature of life. Our preliminary results show that spectropolarimetric signals not only indicate the presence of microbial life but also vary systematically with community composition and dominant metabolic strategies. Such results pave the way to explore microbial life that thrives in a wide range of environmental conditions and towards the remote detection of life beyond Earth.