In a recent Nutrients journal study, researchers provide a critical review of the concept of ‘the core human microbiome.’ Herein, researchers discuss the technical, analytical, and conceptual issues that must be resolved in order to obtain a comprehensive understanding of the core human microbiome.
Study: The Core Human Microbiome: Does It Exist and How Can We Find It? A Critical Review of the Concept. Image Credit: Juliasuena / Shutterstock.com
The core microbiome is of significant scientific interest as a result of the crucial involvement of the microbiome in nutrient absorption, immunological defense, and gut metabolism. Aside from diseases such as inflammatory bowel disease (IBD) that have directly been associated with an altered gut microbiome composition, several other medical conditions such as depression and autism have also been hypothesized to arise due to altered interactions between the gut microbiota and brain.
Over the past several decades, the human microbiome has been the focus of considerable research throughout the world. Several large national and international initiatives, including the Human Microbiome Project (HMP) and MetaHIT, for example, have been conducted to better understand the complexity of the microbiome.
What causes differences in the core microbiome?
Across different geographies and populations, the core human microbiome varies greatly. These differences can be attributed to varying environmental and individual conditions such as diet, host genetics, and various other factors.
Additional differences in the core microbiome can be identified within one individual, as the gut microbiome has a distinct composition as compared to the vaginal and oral microbiomes.
Furthermore, different parts of the gut may have different microenvironments that support a distinct core microbiome. For example, mucosal-associated microorganisms have more profound effects on immune and health indices than luminal and fecal germs.
As compared to mice, gorillas, and chickens, the core human microbiome has a more common abundance of specific species. Furthermore, as compared to rodents and birds, human microbiomes are most analogous to those of gorillas.
Distinct differences also exist between Westernized and non-Westernized populations. In fact, studies have shown that several microbial species abundantly present in one human population may not ubiquitous in other human cohorts. However, Faecalibacterium prausnitzii has frequently been identified in more than 90% of the specimens within six human cohorts.
Approaches to understanding the core microbiome
The human body houses many different types of microorganisms, including commensals and pathogens. The term “core human microbiome” describes the microbiome components that remain relatively constant across time and amongst individuals.
There are primarily four different approaches for determining the core human microbiome, the two most common of which include community composition and functional profile approaches. The community composition approach describes the core microbiome in terms of the common taxa, whereas the functional profile description is based on a group of shared functions.
The ecology method defines the core microbiome based on taxon abundance, interactions, co-occurrence, and other community-level patterns. The stability approach considers characteristics that support community stability and resilience.