Eavesdropping on bacterial conversations: are bacterial signal molecules a universal cue for the recruitment of benthic organisms in the sea?

Primary supervisor: Dr Karen Tait (PML) Email: ktait@pml.ac.uk

Secondary supervisor: Dr Antony Knights (University of Plymouth)

Additional supervisors:

Dr Tom Vance, (PML applications). Email: thva@pml.ac.uk

Anna Yunnie, (PML applications). Email: anyu@pml.ac.uk

Dr Louise Firth (University of Plymouth)

Scientific background

Currently, many anti-foulants are toxic chemicals which have wider implications for the health of marine communities. Research has provided tantalising evidence that a group of bacterial-derived signal molecules may be used as a settlement cue by a diverse range of marine benthic organisms from the smallest bacteria to larger fauna and flora. 

That a bacterial signal is used as a universal cue for settlement by a remarkably wide range of evolutionary diverse benthic species would lead to a paradigm shift in our understanding of benthic community ecology and pave the way for the development of non-toxic methods to control unwanted growth of benthic species. This project will:

  • determine the behavioural response of a range of benthic species to bacterial signal molecules
  • quantify the influence of the signal on settlement in field conditions
  • determine if disruption to bacterial signalling can be used to minimise the effects of biofouling.

Research methodology

The project will use methods developed in our previous work to study the effect of bacterial signals on the settlement behaviour of benthic species (e.g. barnacles, bryozoans, tunicates or mussels). We will also vary substrata, light levels, the presence of adult species and hydrodynamic conditions to determine the relative importance of bacterial signal molecules to settlement. 

Commercially available compounds will be used to determine if signal-blocking can be used as a means of biofouling control.

Training

The student will be hosted at Plymouth Marine Laboratory (Supervisors Karen Tait, Anna Yunnie and Tom Vance) and registered at the University of Plymouth (Supervisors Louise Firth, Antony Knights). 

Thorough training in methods and techniques will be provided including experimental design and statistical analyses, culturing of bacterial strains, spores and larvae and image analysis. 

This project will require field work for animal collection and experiments. The student will also have access to the training provided by the Aries DTP programme.

Person specification

Honours or masters degree (e.g. 2:1 or above) in a relevant subject (e.g. marine biology, ecology, microbiology).

Many marine benthic organisms begin their life in the water column as spores or larvae. The successful transition from a planktonic to a benthic mode of life is a non-random event with many benthic species using myriad cues to aid them in habitat selection, including the presence of a bacterial biofilm 1. Our data and others suggest that the N-acylhomoserine lactone (AHL) group of bacterial signal molecules may also be utilised as a cue for settlement for a diverse range of benthic species 2, 3, 4.

The student will investigate the extent of this signal-mediated interaction by testing the hypothesis that bacterial signal molecules are a universal cue for settlement by benthic organisms in the marine environment. Methodology developed in our previous work will be utilised and adapted where necessary to study the impact of bacterial signals and signal-producing biofilms on settlement behaviour (e.g. changes to motility, crawling on surfaces and permanent settlement) of a range of benthic species (e.g. diatoms, green and brown algae, barnacles, bryozoans, tunicates, molluscs or bivalves) using image analyses.

To date, our experiments have used controlled laboratory conditions (i.e. a simple comparison of the settlement response in the presence or absence of a cue and in plastic dishes with no water flow).

In reality, benthic marine organisms utilise myriad cues when choosing a surface to settle on. By simulating field conditions (i.e. altering substratum material and heterogeneity, light levels, the presence of adult species and hydrodynamic conditions), the student will determine the relative importance of AHLs in the settlement of benthic species.

Increasing restrictions on the use of toxic compounds have increased the need to find alternative ways to inhibit biofouling that are not detrimental to the marine environment. An obvious avenue for exploitation is the disruption of AHL-signalling as a means of biofouling control. 

The student will investigate signal-blocking mechanisms (i.e. commercially available compounds that target signal production) as a means of biofouling control.

Specific objectives of the project are as follows:

  • Determine the behavioural response of a range of benthic species  to bacterial signal molecules
  • Quantify AHL signal strength and their influence on settlement in field conditions.
  • Determine if disruption to bacterial signalling can be used to minimise the effects of biofouling.

There is flexibility in the course of study (i.e. the choice of benthic species to study, the emphasis on ecology vs the more commercial aspects of the project), depending on the interests and experience of the student. 

With guidance and training from the project supervisors, the student will be responsible for experimental design, execution and data analyses. 

Training will be given on the culture of bacteria and biofilm growth, the culture of algae and preparation of algal spores and the culture of invertebrate larvae. 

Extensive training on image analysis and motion tracking will also be provided to fully understand the effect of AHLs on settlement behaviour. Working with PML Applications (Tom Vance), the student will also gain direct experience of working with commercial partners (see below).

References: 1 Hadfield et al (2011) Ann rev mar sci 3: 453-470; 2 Joint et al. (2002) Science 298: 1027. 3 Tait and Havenhand (2013) Molecular Ecology 22: 2588-2602; 4 Dobretsov et al (2007) FEMS microbiol ecol 60: 177-188.

Funding

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, widening participation 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 or 27 February 2019. 

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