Melinda Clark.

Post-Doctorate Researcher
University of California, Berkeley

Ph.D. Microbiology, 2008
Miami UniversityB.S. Biology & Chemistry, 2003
Mount Union College

melinda_clark(AT)berkeley.edu

Office Location: 208 Calvin Hall
Office Telephone: 510-642-1053


Bioprospecting for extremophiles and analysis of physiological responses to biofuel production

Microorganisms have the amazing capacity to adapt to their surroundings and survive harsh conditions. Some microorganisms can thrive at high temperatures, even over 100°C, and pH values as low as 0. Organisms that can survive in these harsh conditions can be valuable assets to various industrial applications. The development of biofuels has recently become a focus of research and cellulolytic substrates are of particular interest to convert into fuels. Currently, processing of recalcitrant substrates like wood would require pretreatment steps before microbial degradation can occur. These pretreatments typically occur at high temperatures and low pH ranges. In order to save the cost of lowering temperatures and increasing pH after pretreatment, it is beneficial to find microorganisms that can utilize pretreated cellulose in the same conditions in which the treatment occurred. Thermal pools provide the perfect environment to search for organisms that can degrade cellulose at high temperatures and potentially low pH. The bioprospecting group within the Clark lab visits various thermal pools within the United States and potentially outside the U.S. collecting water and sediment samples to enrich for organisms that can utilize miscanthus as their sole carbon source. Once an enrichment is identified as a potential source for novel cellulose degraders, those organisms will be isolated and identified. Novel cellulose degraders will be characterized along with the cellulases that these organisms produce. These cellulose degraders will also be considered for co-culture experiments with organisms that can produce biofuels of interest.

After the cellulose material is degraded into sugars, those sugars can be fermented into biofuels. The production of biofuels though can be toxic to the cells that produce them. At increased concentrations, biofuels like ethanol and butanol can denature enzymes and cause membranes to become “leaky”. In order to increase resistance to biofuels, it is important to understand how biofuels affect the cell and how the cell responds to that stress. Currently, experiments include analyzing physiological responses to ethanol and butanol exposure. One study focuses on the shift in lipids within cell membranes when exposed to ethanol and butanol and determining if yeast, bacteria, and archaea respond in a similar fashion. The second study involves analyzing gene expression of E. coli KO11 when grown in the presence of ethanol at various concentrations. Thirdly, once thermophilic, cellulose degraders are isolated, ethanol and butanol tolerance will be analyzed. These isolates will also be evolved for increased ethanol and butanol tolerance by successive transfer.