Over the past decade, the gut microbiome and its effects on human health have become a topic of considerable interest in the scientific community and popular media. The gut microbiome is composed of bacteria that naturally reside in the gastrointestinal (GI) tract, which have an effect on various biological processes such as digestion, metabolism, regulation of the immune system and protection against pathogens. Interestingly, researchers have begun to uncover communication systems that exist between the GI tract and the central nervous system, termed the “gut-brain axis.” For example, gut bacteria can produce hormones and neurotransmitters that affect mood and behavior.

The brain has been considered, historically, to be a sterile environment. A selective filter called the blood-brain barrier is thought to prevent the diffusion of specific biological materials, such as toxic compounds and bacteria, from the blood to the brain. Recently at the 2018 Society for Neuroscience conference in San Diego, a group of scientists from the University of Alabama in Birmingham presented data suggesting the presence of bacteria in the brain tissue of healthy people. Rosalinda Robert’s group usually studies the differences between the brains of recently deceased schizophrenia patients and healthy individuals. Separate from the goal of their investigations, they were surprised to find bacteria in the brains of both schizophrenia patients and healthy individuals. Interestingly, the majority of the bacteria were of three types commonly found in the gut. 

However, since brain tissue was harvested from cadavers, it is possible that bacteria in the air or on surgical tools could have been transferred to the brain during surgery. Alternatively, bacteria from the gut could have leaked through the blood brain barrier after death but before the brain tissue was collected. Further experimental data, that are peer-reviewed by other scientists, will ultimately determine if there is in fact a brain microbiome. If follow up studies rule out the possibility of postmortem contamination, this could lead to a paradigm shift for the fields of neuroscience and immunology. Bacteria in the brain could represent a previously unknown mechanism by which immune system activity within the brain is regulated. 

Managing Correspondent: Jeremy Gungabeesoon

News Article: Do gut bacteria make a second home in our brains? Science Magazine

Original Article: 594.08 / YY23 – The human brain microbiome; there are bacteria in our brains!. Society for Neuroscience – Neuroimmunology: Regulating Systems

Image Credit: Shutterstock