Isolation and Genomic Characterisation of Toluene-Degrading Bacteria

Abstract:

Goal:

This project isolates and characterises microbes with plastic-degrading potential from samples collected around Hong Kong.

Background:

By 2015, the world had produced a total of 7.8 billion tonnes of plastic (Geyer, Roland, et al., 2017). Microplastics, plastics physically degraded over time, are especially hard to remove with current tools and machinery because of their size and quantity. Of all the plastic waste produced, polystyrene (‘styrofoam’) is perhaps the most alarming: this unrecyclable, low density plastic quickly fills landfills, is blown around by wind and carried by the ocean.

Microbes are known to be able to break down some forms of plastic, such as polyethylene (PE) and polyethylene terephthalate (PET), but to date none have been identified that can digest polystyrene. Any bacterium able to digest the polymer must be able to digest a smaller part of the chain. In this investigation, the ability to use toluene as a carbon source is used to screen bacteria because this common solvent contains almost all of the types of bonds present in the repeat unit of polystyrene.

Method:

Bacterial extracts from diverse sources were first grown in LB medium containing toluene; those showing any growth after one week were transferred to minimal medium with 10% toluene as the only carbon source. Selected strains were isolated on LB agar, their DNA extracted and subjected to shotgun sequencing using the Illumina MiSeq platform. Draft genomes were assembled using Prinseq-lite and Newbler. PATRIC was used to annotate and identify pathways of the two isolated genomes.

References:

Geyer, R., Jambeck, J.R., Law, K.L. (2017) Production, Use, and Fate of All Plastics Ever Made, Science Advances, vol. 3(7), e1700782. doi:10.1126/sciadv.1700782.