The human colon is home to trillions of bacterial cells that form a community known as the microbiota. Bacterial communities form in the bowel early in life and undergo compositional developments that are driven by the nutrition of the child. First studied more than 100 years ago, the composition of the microbiota of the child during the exclusively milk-fed period is relatively simple, differing according to whether human milk or cows milk formula is fed to the baby. Once solid foods are introduced, the composition of the microbiota becomes more complex due to the introduction of food components, mostly plant polymers, that are undigestible to humans, but which provide substrates for bacterial growth in the colon. Thus, some dietary components resemble garden fertilisers; they promote the growth of particular bacterial groups that are able to hydrolyse the polymeric substances, as well as those that can ferment the hydrolytic products. Interactions between different kinds of bacteria result in consortia of species which process plant carbohydrates, producing short chain fatty acids. The influence of dietary components on microbiota composition has, in recent decades, been inferred from the analysis of DNA sequences that are informative of bacterial taxonomy (16S rRNA gene), as well as that of the biochemical capacity of the community as a whole (the metagenome). The types of bowel bacteria that occur commonly in human faeces, representing the main metabolic groups in the colon, have been cultivated. High throughput DNA sequencing studies that reveal the complexity and individuality of microbiotas provide platforms to study interactions between bowel bacteria under laboratory conditions. By understanding the bowel ecosystem and its food-bacteria matrices, we may be able to enhance, through nutritional interventions, the establishment of specific consortia in the bowel, and alleviate the symptoms associated with some human conditions and diseases.
Funding Source(s): MBIE and HRCNZ.