Effect of Bioavailable Metal Concentration on Mechanisms of Metal Resistance

EPA Grant Number: U915385
Title: Effect of Bioavailable Metal Concentration on Mechanisms of Metal Resistance
Investigators: Sandrin, Todd Ryan
Institution: University of Arizona
EPA Project Officer: Michaud, Jayne
Project Period: August 24, 1998 through January 1, 2001
Project Amount: $70,935
RFA: STAR Graduate Fellowships (1998) RFA Text |  Recipients Lists
Research Category: Fellowship - Microbiology , Biology/Life Sciences , Academic Fellowships


The objective of this research project is to develop a model system for the elucidation of mechanisms of metal resistance present at varying levels of bioavailable metal and the resulting impact of the activity of these mechanisms on biodegradation.


A model system is being used to investigate two approaches to increase biodegradation in co-contaminated environments and involve: (1) reducing bioavailable levels of metal; and (2) inducing the activity of a highly effective metal resistance mechanism. To reduce bioavailable metal concentrations and thus mitigate the toxic effects of a metal (cadmium) on organic naphthalene biodegradation, a metal-complexing rhamnolipid biosurfactant is being investigated. In addition to its metal-complexing abilities, rhamnolipid exhibits additional properties that may prove integral to enhancing biodegradation in co-contaminated environments. Specifically, rhamnolipid has been shown to increase naphthalene bioavailability and to facilitate lipopolysaccharide (LPS) removal from the bacterial outer membrane, thus further mitigating the toxic effects of cadmium on naphthalene biodegradation. Various divalent cations are being examined for their ability to induce the activity of a highly effective metal resistance mechanism normally inactive at low, but toxic concentrations, of cadmium. The requisite properties of these divalent cations for induction of cadmium resistance will be investigated. Characterization of this resistance mechanism will rely on molecular techniques such as Tn5 mutagenesis.

Supplemental Keywords:

fellowship, co-contamination, biodegradation, metal toxicity, cadmium, naphthalene, rhamnolipid, lipopolysaccharide, LPS, mutogenesis, biosurfactant, metal resistance, bioavailable metal., Scientific Discipline, Toxics, Waste, National Recommended Water Quality, Remediation, Environmental Chemistry, Chemistry, HAPS, Analytical Chemistry, Environmental Microbiology, Biochemistry, Bioremediation, 33/50, Environmental Engineering, bioavailable metal concentration, cadmium & cadmium compounds, contaminated sites, metal resistance, efficiency of bioremediation, cadmium, Cadmium Compounds, metal resistance mechanisms

Progress and Final Reports:

  • 1999
  • 2000
  • Final