Microscopic living organisms (microbes) govern the function of everything. The human body is a great example.
Your body is made of a collection of organs -heart, lung, skin, intestine, all of your glands, etc. Organs are made of several tissues, and tissues are made of individual cells. In total, your body probably contains more than 30 trillion cells. Well, ‘foreign’ bacterial cells living in every nook and cranny of your body outnumber the trillions of cells that make up your tissues and organs. Not only that, but each location of your body has its own distinct community that is well adapted to the conditions of that site and flexibly responds to changes in that environment.
For example, if we were to take a bacteria census on your skin, between your toes, inside your gut, on your ‘private parts’, inside your nostrils, within your middle ear, and on your scalp we would find different ‘demographic’ makeups characterize each site and are subject to change over time. An intuitive analogy is something like gentrification or the result of urban development on pristine land. In both cases, the local animal population (including humans) will change due to changes in the environment. On/ in the human body, the bacterial species composition on your skin and in your gut will change with changes in hygiene routine/frequency or diet, respectively.
The collective microbial population of the human body is called the human microbiome.
Magazine covers from 2012 illustrating just how important discoveries coming from the Human Microbiome Project
A tidal wave of research initiated in 2008 by the National Institute of Health (NIH) (The Human Microbiome Project) has cogently demonstrated that microbes are responsible for the healthy function of our bodies. In the gut, they break down food and extract nutrients that give us energy (Krajmalnik-Brown 2012), regulate our hormones (Martin 2019), they can be the difference between obesity and healthy (Davis 2016), and even regulate our immune systems (Wu 2012). This knowledge is especially relevant when you think about heavy antibiotic use. You can literally destroy your body by ignoring the impact that your microbiome plays in its many functions. The human body is just one of several examples demonstrating that microbes govern the function of all biological systems.
Microbes also serve as the base of all ecological food webs and control the cycling of resources used to sustain life in every known environment on earth from your home garden microbiome to the vast expanses of the global ocean microbiome.
The planet earth functions through several biogeochemical cycles that are dictated by our sun. We homo sapiens are just one link in a long food chain that all begins with photosynthetic organisms. Land plants are a given, but photosynthetic microbes in the ocean are responsible for 48% of global photosynthesis. Therefore, you can thank marine microbes for every other breath you breathe!
