Genomics of Bacterial Resistance to Disinfection

EPA Grant Number: FP916947
Title: Genomics of Bacterial Resistance to Disinfection
Investigators: Berry, David
Institution: University of Michigan
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2008 through September 1, 2010
RFA: STAR Graduate Fellowships (2008) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


The objective of this project is to determine the mechanisms of bacterial pathogen growth in drinking water distribution systems (DWDS). Bacterial pathogens are able to survive and proliferate in DWDS despite the oligotrophic conditions and the presence of a disinfectant residual. The reasons why pathogens grow under these conditions are not yet resolved, but potential mechanisms include protection within biofilms, induction of a disinfectant-resistant phenotype, and intracellular growth within protozoan hosts. All of the proposed mechanisms would be expected to correspond to characteristic gene expression profiles, which could be identified via microarray technology. Gene expression-based adaptive responses may involve general stress responses activated by low nutrient concentrations or sub-optimal temperatures, or alternatively may be responses specific to disinfectant exposure. The gene expression profiles of model microorganisms will be studied using DNA microarray technology under a variety of conditions relevant for DWDS. This knowledge will allow development of strategies for eliminating pathogens from DWDS. In addition, specific genes will be identified that can be used as monitoring and diagnostic tools for utilities.


The gene expression profiles of the bacterial pathogens Escherichia coli and Mycobacterium avium will be studied using DNA microarray technology. The microorganisms will be studied in laboratory-scale reactors under growth conditions relevant to drinking water supply, including: in mixed-species biofilms, in co-culture with protozoa, and with and without monochloramine disinfectant. Pathogens may be protected from disinfectants in niches in established biofilms within distribution systems. Therefore, the growth of natural communities of drinking water biofilms will be studied and the gene expression profiles of constituent species will be analyzed. This process will identify genes that may be useful diagnostic tools to detect entrainment and protection of pathogens within biofilms. The gene expression profiles will be examined to identify (1) expression patterns that are distinctive of disinfectant exposure, biofilm growth, and intracellular growth in a protozoan host, (2) genetic indicators in fluid exiting reactor of previous exposure to biofilm growth or disinfectant residual (3) mechanism(s) for adaptive response to disinfectant residual and integration of known metabolic functions.

Expected Results:

It is expected that distinctive gene expression profiles will be determined that are indicative of disinfectant exposure, biofilm growth, and co-culture with protozoa. This will be useful for identifying the underlying mechanisms of resistance to disinfection. This research is exciting because it will give engineers new tools to analyze, model, and optimize drinking water systems. The application of molecular tools gives drinking water treatment professionals a means to understand and monitor important biological mechanisms and activities that can profoundly affect water quality.

Supplemental Keywords:

drinking water distribution, Escherichia coli, gene expression, genomics, pathogens, microarray, monochloramine, Mycobacterium avium,

Progress and Final Reports:

  • 2009
  • Final