Geological Society of America

T168 Sulfates on Earth, Mars, and Beyond

Tuesday, 24 September 2024
8:00 AM - 12:00 PM
213A

A CASE STUDY ON MICROBIAL COMMUNITIES AND BIOSIGNATURE PRESERVATION IN ACIDIC CAVE GYPSUM

Paper number: T168-5
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Daniel Jones Presenting Author
New Mexico Institute of Mining and Technology, Socorro, NM
Daniel Jones Presenting Author
Carlsbad, NM
Zoe E. Havlena
New Mexico Institute of Mining and Technology, Socorro, NM
Heather V. Graham
Astrobiology Analytical Laboratory, Greenbelt, MD
Jennifer C. Stern
Ancona
Maurizio Mainiero
Ancona
Gabriella M. Weiss
Greenbelt, MD
Gabriella M. Weiss
University of Maryland, College Park, MD
Gabriella M. Weiss
Center for Research and Exploration in Space Science and Technology II, Greenbelt, MD
Angela H. Chung
Astrobiology Analytical Laboratory, Greenbelt, MD
Angela H. Chung
Catholic University of America, Washington, DC
Angel Mojarro
Astrobiology Analytical Laboratory, Greenbelt, MD
Scott D. Wankel
Woods Hole Oceanographic Institution, Woods Hole, MA

Abstract

Gypsum (CaSO₄•2H2O) and other hydrated sulfate minerals are widespread on the surface of Mars, and these evaporite deposits are considered targets for the detection of past and present life. On Earth, gypsum primarily forms in evaporative settings, including in extremely acidic playas that are considered excellent analogues for Martian sediments. However, while acidic gypsum-precipitating environments on Earth often host diverse microbial communities, we don’t know how faithfully these sulfates preserve biosignatures.

In this study, we combined high-throughput rRNA gene sequencing, metagenomics, and cell counts with organic geochemical analyses to explore microbial colonization and molecular biosignature content of extremely acidic gypsum in the Frasassi cave system, Italy. The Frasassi Caves are an active sulfuric acid cave system in which secondary gypsum deposits form above the water table where biogenic sulfuric acid corrodes the host limestone. Gypsum deposits can persist for 100s of thousands to millions of years in sulfuric acid caves, and has the potential to trap organics from the chemolithotrophic microorganisms associated with gypsum formation. We found that freshly-formed gypsum surfaces were colonized by Acidithiobacillus spp. and Thermoplasmatales-group Archaea that, based on previous research and new metagenomic evidence, can produce bacteriohopanepolyols (BHPs) and glycerol dialkyl glycerol tetraethers (GDGTs), respectively. In older gypsum deposits further from the cave water table, these organisms decrease in abundance and are replaced by Alphaproteobacteria and other taxa not associated with fresh deposits. However, despite the active microbial communities, organic biomarker recovery has proven challenging, even from fresh gypsum. In this presentation, we will share results from amino acid and lipid analyses, as well as lessons learned in the search for diagnostic biomarkers in low biomass microbial communities from acidic, oxidizing mineral environments.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405806

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