Research

Project Overview

In many of the worlds oceans, currents carry debris and pollution originating from coastlines. This waste accumulates in regional gyres, where the worlds ocean currents meet, and can reach extremely high concentrations. Plastic is estimated to account for 60-80% of this debris, and is known to be gradually broken down by solar energy and the mechanic action of the sea. This means the majority of the plastic waste are several millimetres in size or less, which has made efforts to clean them from the ocean largely unsuccessful. These tiny plastic fragments - microplastics - enter the digestive systems of resident organism, which are affected either by the physical size of the plastic or its toxicity from adsorbing organic pollutants.

UCL iGEM proposes a synthetic biology approach for the bioremediation of micro-plastic pollutants within the marine environment, with emphasis on regions of excessive debris accumulation, such as the North Pacific ‘garbage patch’.

We intend to engineer enhanced adhesive properties in Escherichia coli and marine bacteria Roseobacter denitrificans & Oceanibulbus indolifex, of the Roseobacter clade. To alter the composition and dynamics of resultant biofilms for the adhesion of micro-plastic pollutants, with an extended vision of creating mass aggregates, or ‘Plastic Islands’.

We will attempt to demonstrate micro-plastic particle aggregation and several additional genetic components, including plastic degradation, salinity/osmotic tolerance in E. coli, bacterial buoyancy and novel active biological containment strategies, for an integrative approach to marine bioremediation.

Biobrick Overview

Module 1: Detection

Our Detection Module will allow our bacteria to detect the presence of plastic. The purpose of this is to control the production of our adhesive – Curli (Module 2) – which binds non-specifically to an extraordinary array of surfaces. By producing adhesive only when plastic is present, we prevent our bacteria binding to non-plastic materials.

Aggregation Module

Curli expression for the aggregation of plastic and production of biofilm BBa_K729003

The Aggregation Module will enable our bacteria to construct islands from smaller plastic fragments. To do so we have decided to transform our bacterium with a circuit to produce an adhesive protein called Curli. As Curlis are non-specific in the surfaces they bind, we also have a module (Module 1) to ensure they are produced only in the presence of plastic

Plastic Degradation

Multi-copper oxidase/Laccase for the degradation of polyethylene and other plastics BBa_K729002

Recent evidence has implicated the role of laccase/multi-copper oxidase in the degradation of polyethylene (Santo et al. 2012). We will investigate the potential of a laccase based BioBrick for the degradation of microplastic debris, with focus on polyethylene and polypropylene.

Buoyancy Module

Temperature dependent buoyancy for localisation of engineered bacteria within the water column BBa_K729000

For optimal aggregation and sustained buoyancy, we propose a method for the localisation of engineered bacteria within the water column, dependent on ambient temperature for the synthesis of the gas vesicle polycistronic cluster(Melbourne 2007).

Salt Tolerance

irrE a global regulator from Deinococcus radiodurans for increased salinity tolerance in E. coli BBa_K729001

irrE, a global regulator of radiation resistance confers resistance to various abiotic stresses through regulation of numerous effectors, including DNA recombination protein recA (Earl et al. 2002). We will specifically investigate the ability of irrE to confer salinity tolerance in E. coli, as previously demonstrated by (Pan et al. 2009).

Containment Components

UCL iGEM 2012 addresses fundamental barriers to the implementation of traditional biological containment systems.

A novel threefold active biological containment system BBa_K729010, BBa_K729009

In view of inactivating mutations and consideration for multiple targets for the induction of cell death, we have devised a robust three fold active biological containment system to address horizontal gene transfer. Consisting of toxin anti-toxin pairs Colicin-E3/Colicin Immunity E3 and EcoRI/methyltransferase EcoRI, in addition to the Holin/Anti-Holin endolysin pair described by Berkley 2008.

Nuclease from Staphylococcus aureus for genomic deletion BBa_K7290011