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Under the Lid – Meet Professor John Ward

Prof John Ward taking water and soil samples from an historic landfill site

John Ward is Professor of Synthetic Biology for Bioprocessing at UCL's Department of Biochemical Engineering. He is also a keen gardener and composter and enjoys isolating novel bacteria from all kinds of environments.

John is interested in looking at how we might use new kinds of bacteria to help break down plastic, which is crucial to our work at UCL's Plastic Waste Innovation Hub where a diverse team of UCL researchers and industry, government, and the public are investigating ways to solve the environmental challenge of plastic waste. One aspect of this research involves finding new types of bacteria that can digest plastic waste. John has been characterising novel bacteria isolated from different soils and composts for several years, and he will be isolating new bacteria from composting plastics that might eventually help to recycle plastic waste.

Bacteria from a wormery in a London school

This bacteria was grown from a sample of ‘vermicompost’ or ‘worm compost’ from a London school wormery. Its colour and size reveals the huge diversity of different bacteria present in the worm compost. The black pigment is probably melanin made by a bacterial colony that secretes an enzyme call tyrosinase. Soil and compost bacteria are often pigmented and the agar plate shows many different pigmented bacterial colonies.

Bacteria from a flower pot at UCL

This bacteria was grown from soil found in a flower pot at UCL. The agar plate shows a background pigmentation of a blue compound called actinorhodin that is secreted from several of the small white bacterial colonies. There is less diversity of bacteria in this micro-environment compared to the rich diversity in the worm compost.

Bacteria isolated from an enrichment composting experiment using PET plastic

This agar plate is a single type of bacterium that we have isolated from an enrichment composting experiment, where small pieces of polyethylene terephthalate (PET) cut from a standard PET water bottle had been incubated for several weeks at 50°C (along with some horse manure). The morphology (shape, size, and colour) of this bacterium when it grows as colonies on an agar plate are quite unusual. The bacterial colonies grow in a sort of expanding ring, leaving no apparent growth in the middle.

Two different dilutions of bacteria from a municipal compost heap in Belfast

A small sample of this compost was suspended in water and then diluted in serial steps of 100 fold before spreading each dilution over the surface of agar plates and growing at 65°C. The sample on the left is a 1:100-fold dilution and the sample on the right is a 1:1000-fold dilution. From this kid of analysis we can calculate the total number of different bacteria per gram in the original compost. There are 13.6 million bacteria per gram in this compost. Each individual bacterial colony from the plates that have well isolated colonies, are picked off and grown individually for analysis. From these bacteria we have already found some high-temperature enzymes such as tyrosinase and proteases.