2025 Theses Doctoral

Uncovering Metabolic Signatures using Lipidomics

Csuka, Joleen

Since the first space probes to Mars, evidence of an active geophysical past and periods of a significantly more temperate environment, suggest an early Martian climate, much like Earth’s. The surface of Mars, now harshly bombarded with ionizing radiation and frigid temperatures, has not yet offered compelling evidence of organic life; however, the subsurface remains a protected environment in which signs of past or extant life may be found.

Future missions to Mars are becoming more enticing as our understanding of habitability is expanded and there becomes a compelling need to find diagnostic biosignatures. Prokaryotes are abundant in the subsurface on Earth, yet remain poorly understood due to their inaccessibility and vast microbiome that contains many unknown species. Compartmentalization using lipids is universal to life as we know it; facilitating complex chemical reaction networks essential to living systems. Lipids are durable, provide structure and protection, and their metabolism and lipophilic intermediates can provide insight into survival strategies of life in all environments.

In this doctoral thesis, I investigated protective isoprenoidal lipids to understand their importance in subsurface lava tubes. I profiled the lipidome of subsurface lava tube microbial samples to showcase their unique fingerprint shaped by their distinct environmental needs. Through the three distinct projects presented in this work, I discuss the validity of lipids as biosignature target molecules and showcase their diversity and detection strategies in Mars analogue lava tubes.