John F. Stolz (’15)

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(Speaker Term: 7/1/13 - 6/30/15)


Department of Biological Sciences
Duquesne University
Pittsburgh, PA  15282 


Phone:  412-396-6333
Fax:   412-396-5907 


Speaker’s URL:




Life in the Frack Pit: The Microbiology of Unconventional Shale Gas Extraction

The extraction of natural gas from unconventional shale gas deposits has grown considerably in the last decade through the combination of horizontal drilling technology and hydraulic fracturing. The Marcellus Shale is a shale deposit formed from an inland sea 390 million years ago that is rich in organics, and the development of this gas play has provided water and increased surface area for microbial colonization in the formation. The condensate tanks and impoundments are also natural incubators for microbial activity. Molecular analyses coupled with enrichment culture have revealed that the produced water from the Marcellus shale has a unique microbiota dominated by halophilic species. This presentation will provide an overview of the processes involved in and the microbiology associated with unconventional gas extraction.            


Microbial Transformation of Arsenic: New Twists for an Old Poison

Arsenic is notorious as a poison with acute doses causing death and chronic exposures resulting in a wide range of maladies. Nevertheless, there are many microorganisms that are not only resistant to arsenic's toxic properties, but may metabolize inorganic and organic forms. Some may even use it to generate energy. Over the past two decades, a robust biogeochemical cycle has been elucidated that involves arsenate reduction and arsenite oxidation, as well as methylation and demethylation. As(V) is a potent electron acceptor used by a phylogenetically diverse assortment of Bacteria and Archaea. As(III) has been shown to serve as an electron donor in photolithoautotrophy and chemolithoautotrophy. Distinct enzymes are involved in arsenic resistance (Ars) and methylation. Three different enzymes have been described for energy generation: arsenite oxidase Aox, respiratory arsenate reductase Arr, and Arx, an arsenic oxidoreductase that looks more like Arr but functions as an As(III) oxidase. This presentation will cover microbial arsenic metabolism and its implications for both the evolution of life on Earth, as well as other planetary systems.  


Microbes, Minerals and Metals: A Microbial View of the Periodic Table

Microbial activity is responsible for the transformation of almost a third of the elements of the periodic table. These transformations are the result of assimilatory, dissimilatory or detoxification processes and form the base of most biogeochemical cycles. These activities can result in the production of nanomaterials, biominerals, and mineral deposits. This lecture will give an overview of microbial arsenic, selenium, chromium, and iron biomineralization as well as the processes involved in the biogenesis of modern marine stromatolites.    


Stromatolites: Over 3.5 Billion Years of "Geobiological" Interactions

Laminated carbonate sedimentary deposits called stromatolites were widespread prior to the Cambrian and provide evidence for the appearance of life and its early evolution. Although limited in global distribution today, living stromatolites are surprisingly abundant in the warm waters of the Caribbean. Their biogenesis has been found to involve several different surface microbial communities and different sedimentary processes (e.g., trapping, binding, lithification). This lecture will describe work on the living stromatolites and laminated microbial communities found in the intertidal waters and ponds on islands in the Exumas.     



Dr. Stolz’s interests are in fundamental questions in microbial ecology as well as the application of unique microbial species for bioremediation. Three major areas of interest of his group are: 1) the ecophysiology, biochemistry, and molecular biology of dissimilatory metal reducing bacteria, 2) the ecophysiology of phototrophic prokaryotes, and 3) bioremediation. Dr. Stolz is well known for his work on microbes, minerals, and metals, with particular emphasis on anaerobic respiration with novel alternative electron acceptors. Respiration using alternative terminal electron acceptors, such as arsenic and selenium oxyanions, is a relatively new discovery and Stolz is a pioneer in the isolation and characterization (i.e., physiology and 16S rRNA) of arsenate- and selenate- respiring bacteria, development of molecular and biochemical probes to identify these species in nature and animal systems, and the characterization of novel terminal reductases (i.e., Nap, DAsR, and DSeR).



Primary Division:  Q (Environmental & General Applied Microbiology)

Secondary Division:  N (Microbial Ecology)

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