Bioremediation of Organophosphorus Compounds
What We Do
Our principal laboratory focus has been on the microbial breakdown of organophosphorus (OP) pesticides. New microbial strains are provided through the implementation of an Environmental Sampling Research Module (ESRM) as part of our undergraduate biotechnology degree that identifies and characterizes microbial isolates for OP degradation from contaminated soil and water reservoirs in the Houston-metropolitan area. Our research has currently identified several distinct special of OP degrading organisms as shown on the table below. In addition to wild-type organisms we have also engineered Escherichia coli to express large quantities of two different OP hydrolytic enzymes. These enzymes include a mature organophosphorus hydrolase (OPH) as well as unique metallo-beta-lacatamase (MBL) that retains hydrolytic activity against OP substrates paraoxon and methyl parathion. We hope to further extend the adoption of this module to other organizations and institutions in the near future.
With a large collection of microorganisms now available we have been able to expand our range of research projects. Our lab has begun preliminary analysis of degradation kinetics for other xenobiotics including herbicides, pharmaceutical waste, petroleum hydrocarbons, 1, 4 dioxane and other industrial solvents. Once a baseline for each organism has been established we alter different environmental and nutritional parameters to determine the effects of biostimulation on microbial growth and degradation. This process allows us to optimize degradation kinetics for each strain based on the desired substrate.
Genomic and Biochemical Analysis
Promising degraders are identified through 16S rDNA sequencing and fatty acid methyl ester (FAME) testing. Cellular DNA is also extracted and probed fro the presence of critical hydrolytic and stress response genes through explorative PCR. Once isolated, each putative degradation gene is cloned into an expression vector and used to transform E. coli cells with the intent of engineering multifunctional microorganisms as control stains.
We are currently looking into attenuation studies to reduce the potential virulence in certain microbial species, specifically Pseudomonas aeruginosa and Stentrophomonas maltophilia. These microorganisms are commonly isolates as part of the ESRM and often possess significant hydrolytic capabilities. Knockout cassettes employing sacB or ccdB will be constructed to generate markerless deletion mutants to reduce potential health risks without compromising the hydrolytic capabilities of each organism. The absence of any foreign DNA in the mutants will be confirmed by PCR and Southern blot analysis. Gene deletion mutants that exhibit insignificant change in growth and degradation dynamics will then be chosen as top candidates for bioremediation.