Immobilized microbial cells grow and produce extracelluar polymeric substance (EPS), which create structured communities of microorganisms. Together, immobilized cells and EPS form a biofilm. Reports from many water utilities in the US have shown that biofilm survives in water distribution systems despite the continuing presence of disinfectants and causes significant health threats to the public. Currently, the persistence of biofilm in water distribution systems is believed to be strongly related to EPS. The principal objective of this proposal is to understand the mechanisms of the persistence of biofilm in water distribution systems. Emphasis will be placed on understanding the role of biofilm EPS, using microelectrodes techniques and fluorescently labeled probes for in-situ biofilm monitoring.
The proposed studies with microelectrodes techniques and biofilm analysis tools will broaden our understanding of pathogenic biofilm formation and its control with disinfectants. Specifically, this research will enable quantitative evaluation of the role of EPS and biofilm structure on the transport and reaction of disinfectants. This will result in the development of modeling parameters obtained with microelectrodes and biofilm analysis. In addition, we will identify the role of EPS on pathogen attachment, detachment and redistribution. Finally, this research will result in combined assessments of the effects of multiple distribution parameters (water age, reactive pipe material, phosphorous corrosion inhibitor) on multi-species biofilm growth. This research has new key approaches which can be differentiated from previous studies. First, the unanswered transport and reaction kinetics of secondary disinfectants in biofilm will be determined with newly developed microelectrodes and in-situ biofilm analysis. Second, a systematic approach will be used to observe the role of EPS on the detachment and redistribution of biofilm, monitoring physiological states of detached clusters which couldn't be understood with particle size analyzers.
Beyond enlarging our understanding of biofilm control in academic society, the proposed research has direct and broad impacts on water utilities, industries, and public health. The information gleaned from this research will enable local water utilities to incorporate biofilm control strategies and enhance our current understanding of biofilm control mechanism in many other industries including medical and chemical industries. The outcomes will contribute to protecting public health by improving the prevention of biofilm related pathogen infection via drinking water and providing a fundamental understanding of the role of EPS against antimicrobial agents. In addition, the proposed project will result in the training and education of two Ph.D students, summer research opportunities for undergraduate and high school students, and implementation of research findings into PIs three undergraduate courses.
Bacteria cells are found in two major types, those that are isolated and those attached to various surfaces. The attached cells grow, reproduce, and secrete extracellular polymeric substances (EPS) that provide structure and protection to attached cells. A fully-formed bacteria and EPS structure existing as a matrix is considered a biofilm. Formation of biofilm has been associated with a broad range of problems and costs billions of dollars each year to various industries. In water treatment and distribution systems, biofilm is ubiquitous and is a constant concern. A common treatment, disinfection by chlorine or other chemicals is oftentimes ineffective according to reports from many water utilities in the US. EPS, which comprises over 80% of the biofilm, is believed to be strongly related to the persistence of the biofilm in water distribution systems. However, the roles and mechanism of EPS enabling persistent biofilm formation in water distribution networks is not yet fully understood. This project, supported by the National Science Foundation, tried to address our current knowledge gap. The project aimed to provide robust and quantitative information about the multiple roles of EPS on formation, structure, survival, and redistribution of biofilm in the water distribution system. From the support, one postdoctoral, two doctoral, five master students, and two high school students received valuable research training. Research findings were disseminated via eleven peer reviewed journal articles, six conference papers, and thirty four presentations at professional conferences and meetings. In addition, findings were shared with local engineers, undergraduate and graduate students, and K-12 students from underrepresented groups.
