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Industrial polymers, microbe-microplastic interactions

Principal Supervisor: Marco Polin, Department of Physics

Co-supervisor: Joseph Christie-Oleza, Warwick School of Life Sciences

PhD project title: Industrial polymers, microbe-microplastic interactions

University of Registration: University of Warwick

Project outline:

We live in a plastic age where the consumption of synthetic polymers is relentlessly increasing every year. Most of the consumed plastic is of single use and, hence, will rapidly end up as waste. Mismanaged plastic waste inevitably enters aquatic systems and ultimately is washed into the oceans: recent estimates show that ~10 million metric tons were dumped in the seas just in 2010, with a predicted 10-fold increase by 2025 [1]. Most plastics are highly durable and therefore expected to persist in the environment for centuries. The ultimate fate of marine plastics and its environmental impact is not well understood. Recent global surveys estimate that the plastic currently floating in the oceans accounts for only ~1% of the total expected marine plastic debris that has been dumped by humans during the past 50 years [2]. The fate of the remaining 99% is unknown. Marine plastics fracture and break due to weathering, and therefore small debris should be much more abundant than large ones. This has indeed been observed, but only down to a size of ~2mm. Below that size a “microplastic gap” appears: a sharp cutoff at the millimetre scale with sub-millimetre size debris strikingly under-represented [2,3]. The microplastic gap signals the importance and unexpected results of microbial interactions with man-made plastic material. This can happen either through direct colonisation of the plastic surface, or by ingestion of small plastic particulates [4]. In both cases, microorganisms are expected to modify the structure of the material, in ways currently not well characterised.

This Ph.D. project will develop critically our understanding of the relation between particulates of different industrial synthetic polymers and marine microorganisms, with the aim of clarifying natural bio-reprocessing of plastics. We will focus initially on PPE and PP but will expand to other industrially-relevant materials through our contacts with WMG. Your research will adopt a two-pronged approach, studying both the large and the small ends of the size spectrum of different biodegradable and non-biodegradable materials. For large plastic objects (~1000-100um), the student will study quantitatively the dynamics of microorganismal colonisation depending on size and plastic type. Size has already been shown to have a strong effect e.g. on microbial colonisation and processing of oil microdroplets from platform spillages [5]. At the small end (<10um), the student will focus on the uptake of synthetic microparticles by marine phagotrophs, already reported anecdotally [6]. The student will start from microfluidic and microscopy techniques, and microbiological assays already available in the groups of Dr. Polin [7] and Dr. Christie-Oleza respectively, and will further improve/refine them.

References:

  1. J. R. Jambeck, et al., Science, 347, 768(2015).
  2. A. Cozar, et al., Proceedings of the National Academy of Sciences (USA), 111, 10239(2014).
  3. www.sciencemag.org/news/2014/06/ninety-nine-percent-oceans-plastic-missing
  4. M. Cole, et al., Environmental Science and Technology, 49, 1130(2015).
  5. Ongoing work by Stocker lab. See http://stockerlab.ethz.ch/research/
  6. D. J. S. Montagnes, et al., Aquatic Microbial Ecology, 53, 83(2008).
  7. R. Jeanneret, D. Pushkin, V. Kantsler, and M. Polin, Nature Communications, 7, 12518(2016).

BBSRC Strategic Research Priority: Bioenergy and Industrial Biotechnology

Techniques that will be undertaken during the project:

The project will require a combination of experimental (general microbiology wetlab) and theoretical/numerical skills (in particular quantitative data analysis and programming).

Contact: Dr Marco Polin, University of Warwick