Title: Microbial source tracking to determine the host origin of fecal contamination in two Puerto Rican watersheds
Duration: March 1, 2002 - February 28, 2005
Critical Water Problems
In the first year of the proposed research, we will isolate a fecal coliform, Escherichia coli, from the feces of a wide variety of warm-blooded animals, including humans, located in two watersheds in Puerto Rico. We will isolate the DNA from these E. coli isolates and obtain a DNA "fingerprint" of each isolate. Each "fingerprint" represents the portion of DNA that encodes for ribosomal RNA (rRNA) and is called a ribotype. The method, called ribotyping, shows considerable promise in being able to associate specific E. coli ribotypes to specific animal hosts. If one then obtains ribotypes of E. coli isolates from waters contaminated with feces, one should be able to identify the sources of fecal contamination by matching the ribotypes from the water against ribotypes contained in a host origin database. This area of research is called microbial source tracking. In the second and third years, we will expand the host origin database and use microbial source tracking to determine the host origin of nonpoint fecal contamination in the Yaguez and Grande de Añasco Rivers.
With regards to the Puerto Rico Water Resources Research Priorities for FY2001, the proposed research responds directly to Priority #1, Watershed and Water Sources Management. Because of ribotyping's discriminatory power, it is possible to identify the contamination source of many E. coli isolates from Puerto Rican water sources. With a suitable host origin database, microbial source tracking offers water resource managers the ability to direct their efforts at controlling sources of E. coli (as fecal coliforms) where reasonable control is possible (e.g., malfunctioning septic drainfields) and not at sources over which they have limited control (e.g., wildlife defecating in the water). The proposal also responds indirectly to Priority #10, Drinking Water Quality Research, because TMDL implementation plans will require identifying the host origin of nonpoint fecal contamination sources. The current method to identify nonpoint sources of fecal contamination, land use, does not work well. Therefore, microbial source tracking with ribotyping offers a better solution than the current method.
Results, Benefits, and/or Information
The main benefit of microbial source tracking, being able to identify the host origin of unknown E. coli isolates (as fecal coliforms) from Puerto Rican water sources, is not possible if a host origin database from a wide variety of warm-blooded animals does not exist. The more extensive the host origin database, the greater the likelihood is of obtaining matches. In the first year, we will obtain the ribotype of 400 E. coli isolates from a wide variety of warm-blooded animals located in two watersheds in Puerto Rico. In this manner, the first host origin database for Puerto Rico will be established. In the second year, we will obtain the ribotypes of an additional 400 E. coli isolates, of which 150 will be used to expand the host origin database, and the remaining 250 will be used to test Yaguez River, a river that is impaired for fecal contamination. The third and final year will repeat the second year sampling except the Grande de Añasco, another impaired river, will be tested.
The benefit of the proposed research is that if water resource managers are able to direct their efforts at controlling sources of E. coli (as fecal coliforms) where reasonable control is possible (e.g., human sewage) and not at sources over which they have limited or no control (e.g., wildlife), then this constructive allocation of Puerto Rican resources would maximize the possibility of improving water quality. With respect to the proposed research, the results will be published in refereed scientific journals, and the host origin database will be placed on the worldwide web so that it is publicly accessible.