Exploring the skin microbiome’s response to chemicals used in skin products

The skin microbiome, like many other human microbiomes, involves a close relationship between the host and the microbes (mainly bacteria). With respect to skin these bacteria are mainly members of the genera Propionibacterium and Stap hylococcus, but Micrococcus and Corynebacterium species also feature and the abundance depends on which site is being sampled. The majority of these bacteria reside at the surface of the skin and to a lesser extent in the sweat and sebaceous glands. Thus any cleaning actions or application of cosmetic products will mainly impact and interact with the microbes on the epidermis.

This project proposal will outline how we can begin to understand how commonly used surfactants, such as Tween or SDS, impact on the most common skin bacteria and ultimately on the skin microbiota in this microbiome. The successful PhD student will undertake research to perform the tasks outlined below:-

Task 1: The impact of cosmetic surfactants on the physiology of skin bacteria: Four skin bacteria Propionibacterium acnes, Staphylococcus aureus, S. epidermis and Micrococcus luteus will be chosen as model organisms since they are among the most commonly observed species found on the skin (Oh et al., 2016: PMID: 27153496). These will be grown and their growth characteristics will be measured with and without the surfactants. This task will define baselines for doses that have an impact on these four bacteria. We will also use BIOLOG’s phenotypic arrays (http://bit.ly/2jFNcAs) to assess the impact of the surfactant on the bacterium’s ability to metabolise different substrates. BIOLOG have develop a 96 well format which allows the researcher to test an organism’s ability to utilise single substrates and thus produce a substrate fingerprint for any given organism in a defined situation e.g. with and without a surfactant. We will use this system to assess the impact of the surfactants on the bacterium’s ability use substrates, which may be present in skin e.g. free fatty acids, squalene, wax esters and metabolites of purine metabolism and glutathione metabolism.

Task 2: The impact of cosmetic surfactants on the skin bacteria’s metabolome: When bacteria grow they use substrates and produce metabolites. In the human microbiome, these metabolites are one of the key mechanisms by which the bacteria interact with the host. In this task we will use the information from Task 1 to assess which substrates these bacteria most readily grow on and how the surfactant affects their ability to use the substrate. From this data we will determine what the bacteria make when growing on these substrates and whether these metabolites are A: affected by the surfactant and B: what these metabolites do to skin cells grown in vitro, for example switching on inflammatory markers e.g. IL-8.

Task 3: Profiling the skin microbiome in situ using metataxonomic tools (16S rRNA gene profiling): The final task will assess how the surfactant impacts the skin microbiome’s bacterial composition in real life. Using volunteers, skin will be swabbed before and after exposure to surfactants. From the swab we will extract DNA and using the MiSeq platform from we will profile the 16S rRNA genes therein to provide a complete snapshot of the total community composition.

The overall deliverable from this PhD project will include an in depth characterisation of the impact of the surfactants on the metabolism of the main bacteria found on skin and how this relates to the skin microbiome itself.

This research project has funding attached. It is only available to UK citizens or those who have been resident in the UK for a period of 3 years or more. Some projects, which are funded by charities or by the universities themselves may have more stringent restrictions.

The ideal candidate will have good laboratory skills and be able to communicate effectively both in reports and verbally. The will be self-motivated with the ability to manage and plan their own workload. Teamwork, attention to detail and problem analysis skills are essential for this role. They will have an A Level in Chemistry and be working toward a 2.1 in a Chemistry or related degree.