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My geomicrobiology research is summarized into two basic themes: 1) understanding
the microbial diversity, ecology, and nutrient cycling of the terrestrial subsurface,
and 2) characterizing the geological and geochemical consequences of microbes
living in their habitats. As a geomicrobiologist, being able to weave together
aspects of many different disciplines is important and my research is strongly
interdisciplinary, involving both field and laboratory work where cutting-edge
geochemical, isotopic, and genetic techniques are used.
I focus my research primarily in karst settings because caves are accessible
analogs to the deeper subsurface. I also have research projects in surface environments,
such as thermal and non-thermal surface-discharging springs and symbiotic systems (including bacteria and clams). Current field sites
include: the Lower Kane Cave and other cave systems in the Bighorn Basin, Wyoming;
the Edwards Aquifer near San Antonio and Austin, Texas; Lassen Volcanic National
Park, California; anywhere there is a sulfur spring, such as Louisiana, Utah,
New York, Colorado, Wyoming, California, Texas, Kentucky, and Indiana; the travertine
and karst regions near Viterbo and Genga (Frasassi Caves), Italy; several caves
in Romania, including Movile Cave; the Caves and Karst of Slovenia, and El Tatio geyser field in the Atacama
Desert, Chile.
Selected Publications
Porter, M.L., Engel, A.S., Kane, T.C., Kinkle, B.K. (2009) Productivity-diversity relationships from chemolithoautotrophically based sulfidic karst systems. International Journal of Speleology. 38(1): 27-40.
Porter, M.L. and Engel, A.S. (2008) Diversity of uncultured Epsilonproteobacteria from terrestrial sulfidic caves and springs. Applied and Environmental Microbiology. 74(15): 4973-4977. doi:10.1128/AEM.02915-07
Engel, A.S. and Northup, D.E. (2008) Caves and karst as model systems for advancing the microbial sciences, in Martin, J. and White, W.B. (eds)., Frontiers in Karst Research, Special Publication 13, Karst Waters Institute, Leesburg, Virginia: 37-48.
Engel, A.S. (2007) Observations on the biodiversity of sulfidic karst habitats. Journal of Cave and Karst Studies. 69(1): 187-206.
Engel, A.S., Lichtenberg, H., Prange, A., Hormes, J. (2007) Speciation of sulfur from naturally-occurring, filamentous microbial mats from sulfidic cave springs using x-ray absorption near edge spectroscopy. FEMS Microbiology Letters. 269(1): 54-62. doi:10.1111/j.1574-6968.2006.00600.x.
Meisinger, D.B., Zimmermann, J., Ludwig, W., Schleifer, K.-H., Wanner, G., Schmid, M., Bennett, P.C., Engel, A.S., and Lee, N.(2007) In situ detection of novel Acidobacteria in microbial mats from a chemoautotrophically-based cave ecosystem. Environmental Microbiology. 9(6): 1523-1534. (included published cover of the issue) doi:10.1111/j.1462-2920.2007.01271.x.
Campbell, B.J.*, Engel, A.S.*, Porter, M.L., and Takai, K. (2006) The versatile Epsilon-proteobacteria: Key players in sulphidic habitats. Nature Reviews Microbiology. 4:458-468. (* equal contribution)