Reduce, reuse and recycle programs are important, but are not enough to address the massive plastic pollution problem facing our planet, and thus this research is focused on the biodegradation of plastics found in our environment. Toward creating a more circular plastic economy, the investigators previously isolated a consortium of bacterial species, five in total, that degrade polyethylene terephthalate (PET), the material used to make plastic water bottles. It was discovered that, collectively, the consortium grew faster on, and produced more plastic-degrading enzyme activity than individual consortia or species alone. This project entails determining the genetic and biochemical basis for these observations. The project provides undergraduate and high school students research opportunities aimed at accomplishing the goals of the research plan. First generation and underrepresented minority students are recruited for summer research and continued effort during the academic year. The genetic basis for bacterial degradation of PET also will be investigated in the laboratory portion of a general microbiology course, providing enrichment the curriculum.
Synergistic degradation of PET plastic by soil bacteria is unexplored but has the potential to aid in the removal of a portion of the estimated 6.3 billion metric tons that currently exist in the environment. Three Pseudomonas and two Bacillus spp. were previously isolated from petroleum polluted soils near Houston, TX, by screening for lipase activity which is associated with plastic degradation. The consortium of five bacterial species were found to act synergistically, producing more lipase activity in degrading PET plastic faster than individual consortia or strains. This project investigates the mechanism of the bacterial degradation process by the consortium. With the assistance of the KEGG pathways database, the project involves mining the genomes of the five bacteria to understand the metabolic pathways necessary for biodegradation of PET. The project uses NMR techniques to determine the breakdown products of PET and related compounds in an effort to identify the enzymes and genetic pathways necessary for this decomposition process. Transposon mutagenesis, an unbiased approach, is used to identify genes encoding lipases, esterases and other enzymes involved in PET degradation. RNAseq analysis is used to determine the interactions between the regulatory networks of the consortia members and the genetic pathways necessary for PET degradation. With the use of RNA sequencing, the project investigates the genetic regulatory network of the consortium bacteria required for ester bond cleavage and the complete degradation of terephthalic acid and ethylene glycol.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
