University of South Florida
College of Arts and Sciences
Contribute to our future
Office: BSF 131
Lab: BSF 243, BSF 245
1992 Ph.D. in Biomedical Sciences. Old Dominion University and Eastern Virginia Medical School.
1983 B.A. in Biology. State University of New York at Plattsburgh.
1980 B.A. in French. Iowa State University.
Water quality microbiology and microbial ecology
Work in my laboratory focuses on water quality. Microorganisms that enter the water via sewage contamination can sicken entire communities and cause death. We are trying to find better ways to determine the source(s) of fecal contamination in water, whether it originates from human sewage, pets, agricultural animals, or wild animals. My lab is best known for its work on microbial source tracking (MST), described below.
Fecal indicator bacteria, such as fecal coliforms, E. coli and Enterococcus species are used extensively in the US and throughout the world as signals, or “red flags” for fecal contamination in water, yet these organisms can enter the water in the feces of animals as diverse as cattle, birds and humans. In subtropical waters such as those found in Florida, there is potential for growth of these indicator organisms. If growth occurs after indicator organisms enter water, sediments and soil, the indicator organism will tend to be present at high levels in the absence of pathogens, nullifying its use as an indicator of water quality and its predictive value for risk to human health. The goal of microbial source tracking (MST) is identification of the source of fecal indicator bacteria, and possibly pathogens, in environmental waters. These studies have implications for how stormwater is managed, how beach water quality is monitored, and how water quality is maintained or improved throughout the U.S. and in other countries.
We employ state-of-the-science methods such as quantitative PCR (qPCR) to quantify genes of bacteria and viruses that indicate contamination from specific sources. We work with state and federal agencies such as the Florida Department of Environmental Protection, the U.S. Environmental Protection Agency and the U.S. Department of Agriculture to develop new methods and test emerging ones in locations ranging from Florida to Arkansas, California, Colorado, New Mexico, Oklahoma, Virginia and New Zealand.
We are also investigating the potential for growth of E. coli, Enterococcus and other indicator organisms in Florida sediments and waters, and the stability of genomic fingerprints for these organisms under environmental conditions. The effect of agrochemicals such as fertilizer, malathion and chlorothalonil on indicator bacteria and pathogens is also under investigation. Community structure and indicator diversity in anthropogenically impacted vs. disturbed environments constitutes another area of ongoing research.
Other research interests also include qPCR quantification and population biology of the marine bacterium Vibrio vulnificus, an opportunistic pathogen that can cause septicemia and rapid death. V. vulnificus is a significant cause of illness and death in Florida and other states, generally due to consumption of raw shellfish but also from wound infections.
Valerie J. Harwood