Examining the impact of air pollution on invertebrates

Overview

In 2018, The Lancet Commission reported that pollution is the top environmental risk to human health – responsible for 16% of all deaths worldwide. Of the numerous air pollutants, particulate matter (PM) was estimated (in 2016) to contribute to 4.2 million premature deaths worldwide per year, brought on by cardiovascular and respiratory diseases. One of the biggest problems related to air pollution is particulate matter (PM) which is a mixture of solid particles and liquid droplets and comes from construction sites, road traffic, power plants, etc. PM varies in size, shape and chemical composition and is classified based on size – either less than 10 (PM10) or 2.5 (PM2.5) micrometres in diameter. In the UK, particulate matter is the fourth greatest threat to public health after cancer, heart disease and obesity.
Interestingly, there is evidence that air pollution also affects insect and plant populations. Certain air pollutants decrease flower scents, and therefore, impact an insect’s ability to locate and forage. And some plants release defensive metabolites in response to air pollutants which negatively affect insect herbivores. Historically, honeybees and bee products have been used to monitor environmental pollution due to their sensitivity to pollutants, ability to transfer contaminants into their honey and high mobility and monitoring area. However, the impact of particulate matter on bee health and immunity is largely unknown. The fruit fly, Drosophila melanogaster is also used to study the impact of air pollution on health and immunity. Particulate matter was found to shorten the lifespan of Drosophila as well as induce inflammation, oxidative stress, and metabolic abnormality. Therefore, air pollution is both an environmental/ecological risk, and a human health issue.
To assess the putative biological impacts of exposure to air pollution, we will use the wax moth (Galleria mellonella), as the innate immune responses, notably phagocyte-mediated pathogen clearance, are highly similar to their human and mouse counterparts. They are amenable to physiological manipulations in their life history and ecology and are ethically more acceptable than animal work. We and others have proved the validity of using G. mellonella as a model organism to study toxicology and microbial pathogenesis (e.g. human pathogenic yeast and bacteria). Now we want to use G. mellonella in ecological and environmental studies. The overall AIM of this studentship is to use G. mellonella to address both the environmental and ecological consequences of air pollution on insect biology by investigating: (OBJ 1) the changes in life cycle of G. mellonella under different air-quality conditions; (OBJ 2) the impact of air quality on the immune system of G. mellonella; (OBJ 3) the mechanism(s) of altered cellular function caused by particulate matter.

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Image Captions

Air monitoring station in Glasgow Kerbside and Glen Finglas Estate (Woodland Trust) – sites for maintaining and monitoring insect life cycle

Methodology

To achieve the abovementioned objectives, the student will:
OBJ 1) Maintain a colony of G. mellonella in the laboratory and retrieve eggs for experiments. Wax moth eggs will be kept in containers with a controlled steady flowrate of outdoor air sampled from urban and rural environments along Scotland’s central belt. S/he will also monitor the levels of common air pollutants (including PM) using an air quality monitor to provide a fuller picture when linking air quality to the insect’s life cycle. Insect’s lifecycle will be monitored.
OBJ 2) Determine if exposed G. mellonella larvae is more susceptible to insect-specific
pathogens, Photorhabdus luminescens (bacterium) and Beauveria bassiana (fungus). S/he
will determine larval survivability, melanisation levels, total haemocyte counts, phenoloxidase / ROS activity (indicators of immunity) and bacterial load (pathogen’s ability to proliferate acts as a proxy for insect’s immune health).
OBJ 3) Expose larvae to standard reference materials such as Diesel or Urban Particulate Matter (DPM or UPM) topically or by intrahaemocoelic injection. Larvae will be monitored for survival and development, gene regulation, haemocyte counts, phagocytic capabilities, antioxidant status and changes in midgut and trachea permeability.

Project Timeline

Year 1

Conduct a literature review and design an appropriate research strategy for work within the laboratory (microbiology/cell biology);
Monitoring of waxmoth exposed to outdoor air sampled from urban and rural environments;
Undergo training in genomics & RNA-seq data analysis;
Undergo training in histopathology;
Attend and present at one local conference.

Year 2

Monitoring of waxmoth exposed to outdoor air sampled from urban and rural environments;
Sequence analysis, biochemical assays and histopathology of waxmoth exposed to air sampled from urban or rural envrionments;
Attend and present at one local/overseas conference.

Year 3

Monitoring of waxmoth exposed to outdoor air sampled from urban and rural environments;
Sequence analysis, biochemical assays and histopathology of waxmoth exposed to air sampled from urban or rural envrionments;
Attend and present at one overseas conference.

Year 3.5

Thesis finalisation and paper writing (although it is anticipated that these activities will be ongoing throughout the PhD).

Training
& Skills

The analytical techniques required for this study are already established at the University of Stirling and include: ICP, SEM-EDS, Histology, microbiological / biochemical assays, using microscopy & plate readers. S/he will receive training in ICP and SEM-EDS via Stirling Analysis for Geoarcheology (http://stag.stir.ac.uk/) and “Linux for Genomics” & “RNA-seq Data Analysis” from Edinburgh Genomics (https://genomics.ed.ac.uk/). I will provide training on experimental design and data analysis related to the project work. Our Division also run courses on Effective Research, Scientific Writing, Statistics for Environmental Evaluation (and use of R) and Presentation Skills.
The student will also benefit from wider interaction within research groups at Stirling and Heriot-Watt. We will establish regular meetings between HW and Stirling to allow discussions on the student’s work. S/he will be expected to present the results of their research annually at the BES student symposium. The student will also be expected to present their work at one local and one overseas conference.

References & further reading

https://www.who.int/en/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health
Fuentes et al (2016) Atmospheric Environ. 141:361-374
Wang et al (2017) Toxicol Sci.156:199-207
Lim et al (2018) J Immunol. 200:3539-3546
Coates et al (2019) Cell Biol Toxicol. 35:219–232

Further Information

Dr Jenson Lim, Jenson.lim@stir.ac.uk, +44 (0)1786 467821
Dr David Brown, d.brown@hw.ac.uk
Dr Heather Price, heather.price@stir.ac.uk +44 (0)1786 467823

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