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Molecular Biology

The Biology Program's Molecular section uses laboratory analyses to identify fecal contamination sources in Florida’s waterbodies. Fecal bacteria are found in human and animal wastes but are also found naturally in soil, sediment, water, periphyton, and biofilms. The exact composition of bacteria differs between source. Standard culture-based methods cannot discriminate enteric (from the gut of a host animal) from environmental (free living bacteria not associated with fecal waste or elevated health risks) bacteria. Microbial source tracking studies help investigate and distinguish the sources.

To perform microbial source tracking, analysts collect and filter water samples to capture bacteria, extract the bacterial DNA, and perform quantitative polymerase chain reaction (qPCR). qPCR amplifies specific DNA sequences and quantifies the amount of amplified DNA present in the sample. This amount will indicate how much fecal bacteria from a specific animal species is present in the sample, which provides information about whether that animal is contributing to elevated bacteria levels. Results from qPCR analyses are used in combination with microbiological and chemical analyses to determine sources of fecal bacteria. Current markers in use are HF183 (human-specific), Gull2 (seabird-specific), and GFD (avian-specific). Validation of new markers to expand the lab’s capabilities is ongoing.

Identifying the source of fecal bacteria is an essential step in prioritizing restoration activities. Levels of bacteria above surface water quality thresholds may lead to a waterbody being classified as impaired. Staff at DEP aim to restore all impaired water bodies but must prioritize those that pose the greatest threat to public health. Waters impacted by human waste are more likely to cause adverse health effects than those impacted by animal waste and are given the highest restoration priority. Microbial source tracking studies help the department identify potential problem areas more quickly and better understand and communicate any risks associated with human exposure. By targeting anthropogenically enriched water bodies for restoration, DEP staff can best protect the health of humans and the environment.

Last Modified:
August 4, 2017 - 9:03am

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