Proteobacteria, for example, includes Escherichia coli (some strains of which are pathogenic) and Salmonella. Within each of these phyla, there are a variety of species of bacteria-more than 1,000 altogether. Of these, Bacteroidetes and Firmicutes are usually the most common. The kinds of bacteria in our gastrointestinal tract fall into five main phyla: Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria and Verrucomicrobia. Because we have such a special, lifelong relationship with our gut microbes, the collective name we give to those in any one person’s gut is their gut microbiome. The collective name for all the kinds of microorganisms that typically live in the gut is the gut microbiota. They make up around 90 per cent of our gut’s population (the remainder includes Fungi and Archaea). is divided up into more and more specific categories (smaller and smaller branches), until we eventually reach the various species.īacteria are single-celled microorganisms with some distinctive cell structures. GLOSSARY phylum plural: phyla a primary division of a taxonomic kingdom. Each of these domains can then be grouped further into more specific categories (think of them like the branches of a tree) called phyla. The three domains are Eukaryota, Archaea and Bacteria, with microbes being found in each.

Let’s zoom in and take a closer look at the kinds of microbes in our gut.įirst of all, it’s useful to know that scientists group all life on Earth into three main groups called domains. However, vast populations of microbes acting together are capable of profound effects. Their small size means that, individually, microbes have almost no impact on us. Some have just one cell, while others are multicellular. Because few microbes can survive the acidic environment of the stomach for long amounts of time, the further you go down the gastrointestinal tract, the more microbes you’ll find.īut what exactly is a microbe? Microbes, also known as microorganisms, are living creatures that can only be seen under a microscope. When we talk about microbes hanging out in the ‘gut’, what we mean is the gastrointestinal tract-the series of long, hollow organs that run in a long, twisting tube from the mouth to the anus-including the oesophagus, stomach, small intestine and large intestine. Estimates are that there are between 30 trillion and 400 trillion microorganisms in the human gut, and from three to 100 times more bacteria in the gut than there are cells in the human body. By far the majority of them, though, camp out in our gut. They’re on our skin and genitals, and in our mouths, ears and sinuses. Trillions of tiny organisms-microbes-are all over, and inside, each of our bodies.

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