Processes of Industrialisation Influencing the Human Oral Microbiome

Abstract

Oral disease affects an estimated half of all people globally—the most common of any noncommunicable disease to be contracted throughout an individual’s lifetime. Yet, despite numerous technological and scientific developments of the past century, the prevalence of oral disease continues to increase alongside urbanisation and industrialised lifestyles; a major public health problem marked with inequalities and ethnic disparities. Critically, oral health is a key indicator of overall systemic health, and thus, the study of the human oral microbial communities has tangible outcomes that can improve—both oral and systemic—health and well-being. Evidence supports a mutually beneficial relationship between humans and their microbiome (i.e. the microorganisms and their genomic content, living on and within the human body), evident by the reliance of human physiological function upon the synergistic interactions with their microbes. Most oral diseases typically stem from a ‘microbial imbalance’, where the disruption of oral microbial ecology no longer supports a symbiotic or mutually cooperating microbiome optimal for human health. In this thesis, I investigate, inform, and improve upon our understanding of the human oral microbiome. I focus predominately on the processes of industrialisation— principally, the consequential alterations to human sociocultural and environmental factors—that are known to influence the microbiome and augment oral disease risk, and by extension, impact human systemic health. Within this thesis, I synthesise our current understanding of and the research pertaining to the human microbiome, advocating for the inclusion of human-microbiome co-evolutionary history within public health and biomedical research. This is especially important regarding the health inequalities impacting Indigenous populations globally, wherein evolutionary life history may underscore contemporary population health. Inclusivity of Indigenous populations within human microbiome research is needed in order to better understand the influence of industrial processes upon the microbiome, especially in regard to human health and disease. I analyse the salivary microbial community of Aboriginal Australian and Torres Strait Islander children, one of the first studies to investigate whole oral community changes in response to oral health treatments. Finally, I sought to examine the historical impact of Industrial Revolution on the European oral microbiome, using novel paleomicrobiological methods that grant access to the preserved microbial communities of calcified dental plaque (calculus). By analysing the methodological bias of taphonomy—the biochemical processes of fossilisation—upon calculus microbiomes, I was able to illuminate the ecological alterations of the human oral microbiome, consequent of 200 years of industrial development, that has cultivated the contemporary European oral microbial composition. My thesis contributes to oral health research by providing context and perspective of evolutionary medicine, with the application of evolutionary history, to oral microbiome research to the realm of contemporary public health. Further, I identify promising and prospective areas for future oral and systemic health research through the investigation of historical Industrialisation and its impacts on the human oral microbiome. The genomic understanding of past and present microbial ecological communities can offer more precise inferences of prevailing sociocultural and environmental forces regarding the risks, contributions, and development of oral disease. I hope, in the endeavour to progress our understanding of the human oral microbiome, this work furthers innovation and technical understanding to improve global population health.