Full-time Faculty

• Geomicrobiology  (GEOL 4084/BIOL 4084 - cross-listed and communication intensive)
• Advanced Methods in Aqueous Geochemistry (Special Topics, GEOL 7900); Environmental Aqueous Geochemistry (Special Topics, GEOL 4002)
• Global Biogeochemical Cycles (Special Topics, Graduate course GEOL 7900)
• Various Graduate Seminars (GEOL 7981, "Microbial Geochemistry;" GEOL 7931, "Karst;" GEOL 7911, "Biogeography")
• International Karst Field School (GEOL 4002)

As a geomicrobiologist, my research focuses on understanding the role of microorganisms in geologic and biogeochemical processes through geologic time, but also on evaluating and assessing the habitat conditions, such as rock type or geochemistry, that influence microbial diversity, community structure, and ecosystem dynamics. Although microbial life has been found in nearly every environment scientists have looked, the deep subsurface is a vast and apparently unending habitat for life. Subsurface microbes harness chemical energy, scavenge nutrients from rocks, and physically change their habitats. I study predominately microbial communities from karst settings because caves are accessible analogs to the deeper subsurface. But, I also have collaborative research projects involving coastal habitats, including grass beds and mangrove swamps with Dr. Laurie Anderson and Dr. Huiming Bao (Dept. Geology & Geophysics) where we are investigating lucinid clams and their sulfur-oxidizing bacterial symbionts. 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 at 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; and El Tatio geyser field in the Atacama Desert, Chile. Another project is being initiated to study sulfur springs in Slovenia.

In the discipline of Geomicrobiology, emphasis is placed on understanding the interactions between microbes and their geological surroundings, and therefore aspects of many different disciplines are interwoven. My research is strongly interdisciplinary and involves both field and laboratory work where cutting-edge geochemical, isotopic, and molecular techniques are used. One project, investigating the speciation of sulfur in microbial mats and other natural habitats, involves the use of the high-tech synchrotron facility, CAMD (Center for Advanced Microstructures and Devices), here in Baton Rouge.

Below are some of the highlighted projects:

The Epsilonproteobacteria is the most poorly characterized class of the Proteobacteria. While more effort has been placed on understanding members of this class from marine environments, including the deep sea hydrothermal vents, very little is known about the importance of Epsilonproteobacteria from terrestrial environments. Recently, my collaborators and I found several novel taxonomic epsilonproteobacterial groups in caves with hydrogen sulfide-rich spring waters. To understand the biogeography and evolutionary history of these terrestrial groups, as well as the diversity and evolution of the class as a whole, many sulfidic cave and spring systems are being studied to demonstrate that these bacteria are important for local and global biogeochemical cycling. This project is currently funded by the National Science Foundation.

Karst is important globally for groundwater and petroleum reservoirs, and appreciating how karst terrains evolve through time will aid in understanding where new resources may exist. Some of the world’s most productive oil reserves are found in carbonate rocks having significant secondary porosity, perhaps generated by sulfuric acid. Based on work in Lower Kane Cave, Wyoming, significant carbonate dissolution occurs in the presence of active sulfur-oxidizing bacteria that colonize subaqueous carbonate surfaces. The sulfur-oxidizers survive at extremely low PO₂, suggesting that karstification may occur at much greater aquifer depths in the absence of oxygen. Several microscopy methods are used to describe the geomicrobiology of carbonate dissolution, including scanning electron microscopy and fluorescence microscopy (combined with molecular tools). Isolation of sulfur-oxidizing bacteria from aquifer habitats will allow measurements of carbonate dissolution rates and will determine what role pH buffering (due to limestone dissolution) has on microbial community structure. This work is being expanded to the Edwards Aquifer in central Texas and deep sulfidic water wells with funding from the Louisiana Board of Regents.

El Tatio is the world’s 3rd largest geyser field, and is located at 4300 m, making it one of the world’s highest geyser fields. There are hundreds of active features at El Tatio. Microbes in the thermal pools are exposed to boiling water, high arsenic concentrations, tremendous UV flux, and solutions supersaturated with respect to silica. The flux of damaging UV radiation is more than 3x what we are bombarded with in the central US. The high arsenic concentrations, coupled to UV-A and UV-B radiation, cause rapid and irreversible DNA damage to unsuspecting microorganisms. The extreme conditions at El Tatio (low latitude, high altitude, high temperatures) make it ideal for study, as the conditions are similar to what we believe early life would have experienced in the Precambrian. In collaboration with researchers from the US, Canada, the UK, and Chile, examination of the El Tatio microbial mats shows that cells are covered with amorphous silica. We are investigating how silica interacts with the cell walls and retards UV penetration into the cell, thereby diminishing damage. Molecular-based studies of the changes in microbial ecology and biodiversity related to physicochemical variations, such as changing arsenic concentrations or temperature, are currently underway. This work is funded by the National Science Foundation.

• Ph.D., 2004, The University of Texas at Austin, Geology
• M.S., 1999, University of Cincinnati, Biology
• M.S., 1997, University of Cincinnati, Geology
• B.A., 1995, Wittenberg University, Geology

Write me to request pdf files, or for a full list go to Research Publications link.

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. (* equal contribution)

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.

Landrum, J.T., Bennett, P.C., ENGEL A.S., Alsina, M., Pasten, P., Milliken, K. (In press) Partitioning geochemistry of arsenic and antimony, El Tatio geyser field, Chile. Applied Geochemistry.

ENGEL, A.S. (In review) Karst microbial ecosystems. Contribution to the Encyclopedia of Geobiology. Springer Encyclopedia of Earth Science Series (EESS).

Paoletti, M.G., Beggio, M., Dreon, A.L., Dorigo, L., Pamio, A., Brilli, M., Bertoni, R., and ENGEL A.S. (In review) Cansiliella servadeii (Leptodirinae) exploit moonmilk for food. Journal of Cave and Karst Studies.

ENGEL, A.S., Paoletti, M.G., Beggio, M., Dorigo, L., Pamio, A., Gomiero, T., Furlan, C., Brilli, M., Bertoni, R., and Dreon, A.L. (In review) Microbial communities from secondary carbonate moonmilk: the base of a cave hygropetric food web? Environmental Microbiology.

Birdwell, J.E., and ENGEL, A.S. (In review) Impact of recharge on chromophoric dissolved organic matter in the Edwards Aquifer, Central Texas. Journal of Cave and Karst Studies.

ENGEL, A.S., and Bennett, P.C. (2008) Lower Kane Cave, Wyoming: Where biology and geology meet, in Rhinehart, R. (ed.) National Speleological Society Rocky Mountain Section Regional field guide, 43-57.

ENGEL, A.S. and K.W. Randall (2008) Microbially enhanced carbonate dissolution in karst aquifers, in Sasowsky, I.D., Feazel, C.T., Mylroie, J.E., Palmer, A.N., and Palmer, M.V., Karst from Recent to Reservoirs, Karst Waters Institute Special Publication 14, 52-56.

ENGEL, A.S., Lichtenberg, H., Prange, A., Hormes, J. (2007) Speciation of sulfur from filamentous microbial mats from sulfidic cave springs using X-ray absorption near edge spectroscopy. FEMS Microbiology Letters. 269(1): 54-62.

Meisinger, D.B.*, Zimmermann, J.*, Ludwig, L., Schleifer, K.-H., Wanner, G. Schmid, M. Bennett, P.C., ENGEL, A.S., Lee, N.M. (2007) In situ detection of novel Acidobacteria in microbial mats from a chemolithoautotrophically-based cave ecosystem (Lower Kane Cave, WY, USA). Environmental Microbiology. 9(6): 1523-1534. (* equal contribution)

ENGEL, A.S. (2007) Observations on the biodiversity of sulfidic karst habitats. Journal of Cave and Karst Studies. 69(1): 187-206.

Campbell, B.J.*, ENGEL, A.S.*, Porter, M.L., and Takai, K. (2006) The versatile Epsilonproteobacteria: Key players in sulphidic habitats. Nature Reviews Microbiology. 4: 458-468. (*equal contribution)

Phoenix, V. R., Bennett, P.C., ENGEL, A. S., Tyler, S.W., and Ferris F.G. (2006) Chilean high-altitude hot spring sinters: a model system for UV screening mechanisms by early Precambrian cyanobacteria. Geobiology. 4:15-28.

Please inquire if you are interested in being an Undergraduate or Graduate Student in Geomicrobiology!!!
Funding is available for M.S. and Ph.D. students in the Depts Geology & Geophysics or Biological Sciences.
 

Current Ph.D.: Brendan Headd

Current M.S.: Lindsey Johnson, Cassie Gray

Current Undergraduates:  Kathleen Brannen (lab manager); Brendan Donnelly, Kelley Gwin, Skylar White

Other Current Affiliates: Eric Prokocki (co-advisor with Dr. Mike Blum, ExxonMobil), Dr. Justin Birdwell (Dept Chemical Engineering), Dr. Janez Mulec (Karst Research Institute, Slovenia)

Graduated Students: Angela Green-Garcia, Kelli Willson Randall