Ecology of Toxin-Encoding Phage: The Search for Environmental Reservoirs

EPA Grant Number: U916166
Title: Ecology of Toxin-Encoding Phage: The Search for Environmental Reservoirs
Investigators: Breitbart, Mya E.
Institution: San Diego State University
EPA Project Officer: Zambrana, Jose
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $82,172
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Biochemistry, Molecular Biology, Cell Biology, Development Biology, and Genetics


The objective of this research project is to determine if natural aquatic environments serve as reservoirs for the temperate phage that carry cholera, diphtheria, shiga, staph, and botulinum toxins.


Free phage in the environment have the potential for the dissemination of toxin genes and the maintenance of virulent bacterial populations. In addition, these phage can lead to disease in the humans and other organisms. By systematically screening water samples using polymerase chain reaction and Southern blotting, I will identify the presence of toxin genes and determine if the gene is present on a free-phage particle or within a bacterium. I also will examine the sequence diversity of the exotoxin genes, and determine if there are alternative hosts for the phage that encode these genes. In the face of a bioterrorism threat, identifying the natural niches of exotoxins is essential for routine monitoring and detection of a possible threat, as well as for containment and management should an outbreak occur. Exotoxins, secreted polypeptides involved in pathogenesis, are among the most deadly substances known. Exotoxins manifest many or all aspects of their associated diseases, and although other pathogenic factors are involved, the host bacterium is relatively innocuous without the exotoxin gene. Therefore, the exotoxin-encoding DNA can be considered the disease-causing agent. Many exotoxin genes are carried on mobile elements such as bacteriophage. Despite this fact, most epidemiological and ecological studies of these infectious diseases have focused on the presence and activity of the bacteria, disregarding the potential role of phage. The presence and survival of toxin-encoding phage in the environment is a virtually unexplored field. Because natural aquatic environments and contaminated water supplies are frequently implicated in the spread and persistence of infectious diseases, it is important to determine if aquatic environments serve as reservoirs for toxin-encoding phage.

Supplemental Keywords:

fellowship, phage, toxin, exotoxin, polymerase chain reaction, PCR, genes, contaminated water, reservoirs, virulent bacteria.

Progress and Final Reports:

  • 2003
  • 2004
  • Final