Microbes, the oldest form of life on the Earth, are single-celled organisms. They are so small that millions of them could easily fit into the eye of a needle. We can see them only when we look through high-powered microscopes. Microbes include bacteria, archaea, protists and fungi. Viruses do not belong to the world of microbes because scientists do not consider them “alive.” (Viruses lack many of the properties associated with living organisms; for example, they are unable to reproduce without the help of a host cell, and they do not replicate by means of cell division.)

Certain types of microbes can survive in extreme conditions. Some microbes can remain well preserved in liquid nitrogen at a temperature of -196 Celsius (-320 degrees Fahrenheit), and some microbes can survive high dosages of ionizing radiation, high pressure and temperature. Scientists have learned the hard way just how tough microbes could be when NASA specialists were getting the Curiosity rover ready for its journey to Mars.

In order to sterilize the rover in accordance with a special NASA protocol, scientists “baked” the Curiosity rover at 110 degrees Celsius (230 degrees Fahrenheit) and disinfected it with alcohol. Then, before sending the “germ-free” Curiosity rover to Mars, scientists swabbed it and discovered that 65 species of bacteria survived the whole sterilization procedure. Scientists further exposed the bacteria to dehydration, ultraviolet radiation, pH extremes and very low temperatures.  Almost 11 percent of the strains survived one or even more than one of these extreme conditions! (A strain is a subset of a bacterial species that differs from other bacteria of the same bacterial species in some properties.)

With their ability to endure harsh conditions, it is no wonder that microbes are among the most ancient life forms that ever populated the Earth. Microbe fossils date back more than 3.5 billion years, when water in the oceans was so hot that its temperature could reach the boiling point. When animal life emerged on the Earth about 800 million years ago, microbes had already existed on our planet for approximately 3 billion years.

In many ways, microbes have played a significant role in making our planet and life on our planet what they are today. Without microbes, plants would not be able to grow, there would be significantly less oxygen in the Earth’s atmosphere, garbage would not decay and humans would be very different from what we are today also.

As plants and animals came into existence, they became dependent on their interaction with microbes. Plants were able to colonize the surface of our planet thanks to the microbes, which still help plants extract important nutrients from soil. Microbes also populated animals’ guts, helping them to absorb nutrients from food that animals would be unable to digest otherwise. In return, microbes gained mobility by travelling in animals’ guts.

Today, scientists are studying various functions that gut microbes perform in order to understand how they influenced the evolution of animals and humans. The newest research shows, for example, that gut microbes can prevent closely related species from cross-breeding. Robert Brucker and Seth Bordenstein, biologists at Vanderbilt University, have discovered that the gut bacteria of two species of wasp, which diverged relatively recently, do not allow the species to “reunite.” The two species have slightly different populations of gut microbes. When wasps from the two species try to cross-breed, the hybrids acquire a dysfunctional “family” of gut microbes that leads to their deaths.

Bordenstein points out that this discovery might prove that these gut microbes evolve with their hosts and affect biodiversity. Jürgen Gadau, a biologist at Arizona State University, proposes that the gut microbes can change very quickly, influencing the origin of species. Yet, scientists know very little about the evolution of gut microbes and how their evolution has affected the evolution of the human genome. Modern studies mostly concentrate on researching the impact of modern gut microbes on animal and human health.

Today, microbes continue to flourish on our planet, vastly outnumbering humans. In fact, the number of microbes that live on one human hand can be greater than the total number of humans on the planet! Bacteria make up around 30 percent of the Earth’s biomass. We can find microbes everywhere: in the air, in the ground, in the water, in the food, on the surface and inside our bodies.

Bacteria were discovered in the late 17th century by Antonie van Leeuwenhoek, the Dutch tradesman and scientist who observed these tiny life forms through a microscope. In the 19th century, Ilya Mechnikov, the Russian-born biologist, discovered a connection between human life expectancy and a healthy balance of bacteria in the human body. He also proposed that the number of good bacteria living inside a healthy human body must be greater than the number of bad bacteria.

The latest scientific studies conducted around the world now agree with the idea that bacteria that live in the human gut greatly affect human health and that problems with gut bacteria can even result in brain diseases. The findings of these studies, which have been available for years, are reviewed and discussed in Dr. David Perlmutter’s book, Brain Maker: The Power of Gut Microbes to Heal and Protect Your Brain–for Life. He advocates in his book the idea that the current “epidemic” of brain disorders can be directly related to the notion that many people’s guts are lacking a healthy and diverse microbial population.

Perlmutter is a board-certified neurologist and a well-known researcher in the field of nutritional effects on neurological disorders. His approach to treating neurological disorders is based on the principles of preventive medicine. Perlmutter has extensively communicated to the public the importance of understanding that various brain problems may be prevented via lifestyle changes that include a gluten-free, higher fat and lower carbohydrate diet combined with exercise.

In Brain Maker, Perlmutter explains the powerful interaction between intestinal microbes and the brain. He describes how the microbiome develops in the human body from birth and undergoes changes based on lifestyle. He also discusses conditions that can lead to an unhealthy microbiome. The main thesis of his book, Brain Maker, is that nurturing gut health can enhance brain function.

Perlmutter proposes in Brain Maker that a dietary prescription can heal the gut bacteria, preventing chronic inflammation and the action of free radicals. Perlmutter’s practical regimen comprises six important keys: prebiotics, probiotics, gluten-free foods, low-carb foods, fermented foods and healthful fat. Perlmutter further advocates such treatments for restoring and supporting gut health as probiotic enemas and fecal transplantation.

In the third section of this book, “A Critique of the Principal Messages in Brain Maker,” you will find a review of the findings of medical studies, which indicate that good diet, exercise, probiotic enemas and fecal transplantation, as well as avoidance of unnecessary stress and antibiotics may not be sufficient to heal the sick gut.

Go to Part I A Summary of Research

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