March 07, 2023
Jovana Jovanovska
Testing human skin’s microbiome to determine species diversity in a biogeographic context - makeup application as a disturbance factor
The skin is the largest human organ and the first physical barrier preventing foreign pathogens, hence it is constantly exposed to the surrounding environment and can be easily colonized by microorganisms (Datir et al., 2020). It is populated by bacteria, viruses, yeasts, fungi, and archaea, and they form their own microbiota on the surface (Datir et al., 2020). The human body including the skin is composed of different niches which have their own specific interactions with systems in the body. Each niche represents a distinct habitat for microbial survival (Zhou et al., 2013). Since the skin has multiple niches, it makes it a testable study-site for biogeographic concepts. However, there are several factors that should be put in consideration. Firstly, studies have determined that there are differences in the composition of bacterial taxa in different body parts (Hulcr et al., 2012). Furthermore, there is a high variation of microbial composition among individuals hence it is beneficial to have larger subject numbers to determine trends (Zhou et al., 2013). Other factors about the host, such as sex, age, and environmental exposures can also have a significant effect on the niches and microbiome communities (Bjerre et al., 2017).
For our experiment, we used the human body, and specifically the eyelid in order to test and record species abundance, richness, and diversity. Learning more about the microbiota of the ocular surface is useful in determining whether certain health issues are
caused by the dysregulation of the microbiome, and it also adds in the discussion of whether different systems can be used to test biogeographic theories (Ozkan et al., 2017). In this study, following the intermediate disturbance theory, we hypothesize that people in the group that apply makeup often cause intermediate disturbances in the eyelid microenvironment that results in highest biodiversity and species richness of the eyelid microbiome. Secondly, we predict that people that constantly wear makeup would repeatedly be exposed to disturbances and would have lower diversity. Lastly, we predict that the lowest species diversity would occur in people that never wear makeup, since there are no disturbances in the environment.