Project title:
Plastic oceans, can microbes clean our mess?
Host institution: University of Warwick
Key words:
Marine ecology, microbial community, plastics degradation,
metagenomics, metaproteomics
Supervisory team (including institution & email address):
Joseph A. Christie-Oleza, University of Warwick, J.Christie-Oleza@warwick.ac.uk
Matthew I. Gibson, University of Warwick, M.I.Gibson@warwick.ac.uk
Overview:
Are marine microbes capable of degrading
synthetic polymers such as plastics? Who
and how do they carry out this process?
Plastics have become the major
contaminant in the world’s oceans (Law et
al 2010). The existence of a “plastic island”
twice the size of Texas drifting around the
North Pacific gyre has become a public
concern. In fact, there is data that shows
the existence of giant plastic islands in each
one of the five ocean gyres as hundreds of Figure 1: Scanning electron microscopy image of
thousands of tonnes of plastic waste have the microbial community colonising plastic marine
been dumped into the oceans since the debris (image modified from Zettler et al 2013)
start of the plastic era.
Recent studies have focussed on the microbial surface colonisation of these floating plastics
indicating a high diverse community that differs enormously from the indigenous free-living
marine community (Zettler et al 2013; Oberbeckmann et al 2014). These studies have also
raised concerns on the fact that polymers, mainly in the form of microplastics, accumulate
persistent organic pollutants and harbour harmful microbial species that can easily enter the
food chain. Biodegradation of plastics in aquatic systems has been suggested by pits visualised
by scanning electron microscopy (Figure 1). Plastic degradation has been reported for land
waste plastics and is mainly carried out by fungi and bacteria (reviewed in Ghosh et al 2013).
Unfortunately, very little is known on this process in marine systems.
Methodology:
This PhD Project aims to answer key ecological questions on the biodegradation of plastics in
marine systems. The successful student will analyse the microorganisms that carry out such
vital bioremediation process, investigate the enzymes involved and the biodegradability of
different polymers.
Different well-defined polymers generated in the Department of Chemistry will be subject to in
situ colonisation by natural marine microbes. Colonised plastics will be processed in the lab to
determine: microbial community evolution, metagenomic analysis (using high-throughput
sequencing), metaproteomic analysis of the exoproteome (looking for relevant secreted
enzymes; using high-throughput proteomics), biodegradation of the polymers (light scattering
and chromatography systems to determine the kinetics of degradation), visualisation of the
polymer surface after colonisation (scanning electron microscopy) and, ultimately, isolation
and characterisation of microbial degraders.
The student will have the opportunity to develop his own experiments comparing the
biodegradability of different polymers in natural aquatic environments and the conditions that
may accelerate the process. The identification of microbial degraders and the repertoire of
exoenzymes used to hydrolyse polymers will have important biotechnological applications.
Training and skills:
This multidisciplinary PhD project will offer a unique opportunity for the student to learn stateof-the-art techniques in environmental –OMICS (such as high-throughput proteomics and
genomics), microbial ecology and biochemistry, and analytical chemistry of plastic polymers.
The laboratories of supervisors Dr Christie-Oleza (School of Life Sciences) and Dr Gibson
(Department of Chemistry) are excellently equipped to carry out this cutting-edge project.
Applicants: We are looking for enthusiastic applicants with BSc or MSci in Biology,
Biochemistry or related fields. Applicants with 1st class degrees and laboratory experience will
be valued.
Possible timeline:
Year 1: Synthesis of different polymers and in situ colonisation of marine microbes.
Analysis of community evolution, metagenomics and exoproteomics analysis. Search
for hydrolytic exoenzymes. Evaluation of polymer degradation under different
incubation conditions.
Year 2: Collection of old marine plastic debris with well established microbial
communities. Characterisation and evaluation of polymer degradation. Co-incubation
of marine debris with newly synthesised polymers to visualise colonisation and
evaluate faster biodegradation rates when compared to experiments carried out in
year 1.
Year 3: Isolation of potential microbial degraders. Characterise their exoenzymatic
repertoire for degrading polymers.
Further reading:
Christie-Oleza et al (2012) Mol Cel Proteomics, 11: M111.013110.
Ghosh et al (2013) Environ Sci Pollut Res Int, 20: 4339-4355
Law et al (2010) Science, 329: 1185-1188
Oberbeckmann et al (2014) FEMS Microbiol Ecol, doi: 10.1111/1574-6941.12409
Zettler et al (2013) Env Sci Tech, 47: 7137-7146
Further details:
Potential applicants are invited to contact:
Joseph Christie-Oleza (j.christie-oleza@warwick.ac.uk)