The Human Gut

Overview

By Mia Tran

Representation of the role of the human gut microflora in regulating bodily functions, human health and disease. By Dr. Ana M Valdes at the University of Nottingham.

The human gut, also known as the gastrointestinal (GI) tract, consisting of all the organs that allow for humans to consume, digest, and expel food, and is highly populated by a diverse range of microbiota that serves many crucial processes in maintaining human health, such as digestion, fighting infection, and production of key vitamins and antioxidants. The microbes occupying the gut ranges to the order of 10¹⁷ and consists primarily of bacteria, but also includes a variety of protozoa, archaea, prokaryotes, and viruses.

Detailed Environmental Description

The physical environment of the GI tract consists of an interface ranging from 250-400 square meters in an adult human. The distribution of microbiota within this interface depends greatly on various gradients existing in the gut, such as nutrient and chemical gradients. Microbes tend to sit either in the lumen or mucosa, and very rarely penetrates the bowel wall, as most microbes that achieve this tend to be pathogenic.

The biogeochemical landscape of the gut various from organ to organ. The small intestine, the first organ in the tract following the stomach, is characterized by low pH, high oxygen, and an abundance of antimicrobials. These conditions allow for limiting microbe growth, just so facultative anaerobes begin to settle to the mucus lining of the intestine, making way for an environment conducive for obligate anaerobes. In the colon, or large intestine, there is a much more densely populated and diverse microbiota. Communities of bacteroides, streptococci, and clostridia can outnumber facultative anaerobes up to a ratio of 1000:1.

The study of microflora in the human gut began in 1970s, where a lot of initial research began with studying the composition and count of microbes. At the time, most of the work being done focused on strains that could be cultured. Since then, research exploded during the 2000s and 2010s due to the development of sequencing technologies that allowed scientists to learn about communities that could not be cultured in the lab.

Overview of Microbial Ecology as it is known

(To be added). Discuss the alpha and beta diversity of the system. Include some current research, with at least one figure showing data.

Key Microbial Players

In all of your systems there will be at least a couple of key microbial players. Describe these in detail. Where do they fall on the tree of life? Are they cultured? What do they do in general and as it relates to your target environment?

References

Authored for Earth 373 Microbial Ecology, taught by Magdalena Osburn, 2020, NU Earth Page.