Expertise

Geomicrobiology, Biogeochemistry, Microscopy, Spectroscopy

Research

My research investigates microbe-mineral interactions in the context of microbial physiology, biogeochemistry and astrobiology. The focus is on interactions between sulfate-reducing microorganisms (SRM), which are ubiquitous in anoxic sedimentary environments, and iron sulfide minerals. I use microscopy and spectroscopy to 1) understand the properties and transformation pathways of iron sulfide minerals in anoxic environments and at the oxic-anoxic interface; 2) evaluate if the composition, morphology and mineralogy of biominerals is unique enough to serve as biosignatures for the search of life on other planets; and 3) assess the role of minerals on microbial activity and survival.

Selected Publications

• Nabeh, N., Brokaw, C., & Picard, A. (2022). Quantification of organic carbon sequestered by biogenic iron sulfide minerals in long-term anoxic laboratory incubations. Frontiers in Microbiology, 1360.
• Picard, A., Gartman, A., & Girguis, P. R. (2021). Interactions between iron sulfide minerals and organic carbon: implications for biosignature preservation and detection. Astrobiology, 21: 587-604.
• Picard, A., Gartman, A., Cosmidis, J., Obst, M., Vidoudez, C., Clarke, D. R., & Girguis, P. R. (2019). Authigenic metastable iron sulfide minerals preserve microbial organic carbon in anoxic environments. Chemical Geology, 530: 119343.
• Picard A., Gartman A., Clarke D.R., Girguis P.R. (2018) Sulfate-reducing bacteria influence the nucleation and growth of mackinawite and greigite. Geochimica Cosmochimica Acta, 220: 364-387.
• Picard A., Kappler A., Schmid G., Quaroni L., Obst M. (2015) Experimental diagenesis of organo-mineral structures formed by microaerophilic Fe(II)-oxidizing bacteria. Nature Communications, 6 : 6277.