Diatom-bacteria interactions: deciphering impacts on algal bloom regulation and toxicity

Primary supervisor: Dr Katherine Helliwell (Marine Biological Association). Email: Katherine.helliwell@mba.ac.uk

Secondary supervisor: Dr Michael Cunliffe (University of Plymouth, Marine Biological Assocation)

Additional supervisor: Professor Willie Wilson, (University of Plymouth, Marine Biological Assocation). Email: wilwil@mba.ac.uk

Scientific background

Marine phytoplankton play a vital role in regulating our global climate, contributing almost half of the biosphere’s net primary production. Diatoms are one of the most important phytoplankton groups, generating as much organic carbon as all terrestrial rainforests combined.

Diatoms can also form spatially extensive algal blooms that exert global-scale influences on biogeochemical cycles and underpin many marine ecosystems. Due to the release of harmful toxins, some diatom blooms can also have a negative impact on marine habitats and fisheries.

The biotic interactions of diatoms with predators, parasites, competitors and symbionts, can profoundly influence natural diatom populations, and are an important factor regulating bloom dynamics and toxicity.

Despite the clear importance of such interactions for diatom ecology and marine ecosystem functioning, little is known about the mechanisms diatoms employ to i) recognise and respond to other microbes, or ii) regulate the production of harmful toxins.

These represent important knowledge gaps that need to be addressed, in order to better understand factors governing diatom bloom formation and toxicity.

Primary objectives:

1)  Isolate and identify diatom-associated bacteria from diatom bloom.

2)  Examine the impact of algicidal bacteria on diatom growth, cell physiology and toxicity.

3)  Develop genetically encoded metabolic biosensors to examine cell-signalling processes in toxic diatom species.    

4)  Identify and characterise signalling pathways employed by diatoms to sense and respond to bloom-associated bacteria using live-cell imaging coupled with CRISPR-Cas9 gene editing approaches.

Research methodology

This PhD will couple field sampling at the Western Channel Observatory coastal Station L4, which has regular diatom blooms, with state-of-the-art cell biological approaches in the laboratory.

Field sampling will enable isolation of diatom-bloom associated microbes that will be brought into the laboratory for further experimentation.

A combination of physiological (co-culturing), metabolomics and molecular approaches will be employed to examine the nature of such interactions, and their impact on diatom toxicity.  


The successful candidate with gain training in cutting-edge cell and molecular biology approaches including live-cell imaging (e.g. confocal microscopy), CRISPR-Cas9 gene knock-out, genetic transformation, bioinformatics, and cloning, alongside microbial physiology and environmental microbiology techniques. Professional development, including training in core verbal and written communication, research and analytical skills will also be provided.

Person specification

An enthusiastic, motivated individual interested in how molecular mechanisms in the cell impact ecosystem level processes, with a relevant biological sciences degree (marine biology, microbiology, plant sciences).


1) Helliwell K. E., Pandhal J., Cooper M, Longworth J., Kudahl U., Russo D., Tomsett E., Bunbury F., Salmon D., Smirnoff N., Wright P., and Smith A. G., (2018). Quantitative proteomics of a B12‐dependent alga grown in coculture with bacteria reveals metabolic tradeoffs required for mutualism. New Phytologist. 217(2): 599-612.

2) Kazamia E., Helliwell K. E., Smith A. G. (2016). How mutualisms arise in phytoplankton communities: building eco-evolutionary principles for aquatic microbes. Ecology Letters. 19(7):810-822

3) Helliwell K. E., Chrachri A., Taylor A., Koester J., Wharam S., Wheeler G., and Brownlee C. Novel classes of voltage-gated Na+ and Ca2+ channels play important signalling roles in unicellular eukaryotes. In review.

4) Taylor JD, Cottingham SD, Billinge J & Cunliffe M (2014) Seasonal microbial community dynamics correlate with phytoplankton-derived polysaccharides in surface coastal waters. The ISME Journal 8: 245–248.

5) Taylor JD & Cunliffe M (2017) Coastal bacterioplankton community response to diatom-derived polysaccharide microgels. Environmental Microbiology Reports 9: 151–157.


This project has been shortlisted for funding by the ARIES NERC Doctoral Training Partnership. Undertaking a PhD with ARIES will involve attendance at training events.

ARIES is committed to equality & diversity, and inclusion of students of any and all backgrounds. All ARIES Universities have Athena Swan Bronze status as a minimum.  

Applicants from quantitative disciplines who may have limited environmental science experience may be considered for an additional 3-month stipend to take appropriate advanced-level courses.

Usually, only UK and EU nationals who have been resident in the UK for three years are eligible for a stipend. Shortlisted applicants will be interviewed on 26/27 February 2019.

For further information please see www.aries-dtp.ac.uk or contact us at aries.dtp@uea.ac.uk.