The Gut Microbiota of Bali among the World Populations: Connecting Diet, Urbanisation, and Obesity.

Abstract

Community assembly of the gut microbiota is believed to be achieved through an interaction between the host’s lifestyle and genetic. Failure to address these population-specific factors may lead to unsuccessful detection of obesity patterns in the human gut microbiota. This thesis aimed to extricate lifestyle and genotypic patterns from the human gut microbiota, and to identify obesity patterns in the microbiota of a population with defined lifestyle and ethnogeography. This study utilized the unique cultural and ethnogeography characteristics of Bali people. In the first part of this thesis, the faecal microbiota of 36 ethnic Balinese individuals was compared by obesity, diet patterns (through food frequency questionnaire), and genetic lineage (through mitochondrial DNA [mtDNA] haplotyping). Subjects with non-R mtDNA haplogroup were found to have a higher prevalence of Prevotella-dominated enterotype and higher risk of developing obesity. Moreover, the enterotypes were found to be linked to long-term diet patterns, particularly to choices of staple foods in meals. In the second part of this thesis, the microbiota of 41 Bali individuals was contrasted with the microbiota of 283 other people from 7 ethnogeographically distinct rural and urban populations. Principal Coordinate Analyses of the unweighted Unifrac distance placed Bali individuals between the rural and urban samples, reflecting Bali’s status as a newly-industrialised society. Urbanisation is also associated with the abundance of Prevotella and Bacteroides across populations, but not obesity. Collectively, these findings highlighted that perpetuating host factors (lifestyle, genotype) are drivers of microbial community assembly in the human gut. Importantly, this thesis showed that understanding the genetic and socio-cultural context of a population could be the key to effective identification of microbial biomarkers in obesity.