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81-14 Free and Sulfurized Lipids from the Phototrophic Microbial Consortia of Cape Cod, Massachusetts

Session: New Advances in Geomicrobiology

Presenting Author:

Fatima Husain

Authors:

Husain, Fatima¹, Rohret, Shari M.², Dumit, Diana³, Uveges, Benjamin T.⁴, Liu, Xiaolei⁵, Ma, Jian⁶, Bernhard, Joan M.⁷, Summons, Roger E.⁸r> (1) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA, (2) Department of Geology and Geophysics, Woods Hole Oceanographic Institute, Woods Hole, Massachusetts, USA, (3) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA, (4) Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA, (5) School of Geosciences, University of Oklahoma, Norman, Oklahoma, USA, (6) School of Oceanography, Shanghai Jiao Tong University, Shanghai, China, (7) Department of Geology and Geophy, Woods Hole Oceanographic Institute, Woods Hole, MA, USA, (8) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA,

Abstract:

Along the coastlines of Cape Cod, Massachusetts, brightly colored microbial aggregates colonize the sediment-water interfaces of ephemeral salt marsh pools. These millimeter-scale pink and green aggregates, informally referred to as “berries,” constitute syntrophic sulfur-cycling communities comprised of purple sulfur bacteria, sulfate-reducing bacteria, cyanobacteria, and diatoms. Recent organic geochemical examinations of carbon cycling in euxinic environments have revealed that lipids, biomolecular components of cellular membranes, signaling pathways, and energy stores, can be subject to rapid sulfurization, enhancing their long-term preservation in sediments. To characterize the carbon cycling mechanisms in the microbial aggregates, free and sulfur-bound lipids were isolated from berries collected at two field sites: the Great Sippewissett Salt Marsh of Falmouth, Massachusetts and the West End Salt Marsh of Provincetown, Massachusetts. Sulfur-bound lipids were subjected to desulfurization prior to instrumental analysis. A variety of acetogenic and isoprenoid lipids were recovered from both marshes, including fatty acids, steroids, hopanoids, and aromatic carotenoids. These lipids were analyzed via gas chromatography mass spectrometry, liquid chromatography mass spectrometry, gas chromatography combustion isotope ratio mass spectrometry, and elemental analyzer isotope ratio mass spectrometry. Findings from these analyses were used to establish an inventory of lipid isotopic offsets for purple sulfur bacteria and environmental cyanobacteria, which both perform Calvin-Benson-Bassham cycle carbon fixation. These offsets were additionally compared to characteristic lipid isotopic offsets previously established for cultured cyanobacteria. Altogether, these findings may aid future source-lipid assignment efforts during the biogeochemical analysis of ancient environments.

Free and Sulfurized Lipids from the Phototrophic Microbial Consortia of Cape Cod, Massachusetts

Description

Session Format: Oral

Presentation Date: 10/11/2026

Presentation Start Time: 05:00 PM

Presentation Room: CCC, 105

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