Tantalizing Evidence of a Brain Microbiome

By now, almost everyone has heard of the human microbiome – the collection of viruses, bacteria, and fungi that play a pivotal role in our health and cognitive functioning. Also called the microbiota, we’ve long assumed that the microbiome consists of microbes that reside along our gastrointestinal tract – and more recently, on our skin. That’s logical enough; microbes live on our interfaces with the outside world. Conversely, there are certain areas in the human body that are assumed to be sterile, aka free of microbes, like the eye and the womb. However, advances in analytical techniques enabled researchers to recently identify the placental microbiome1 and eye microbiome2 that are present in healthy people. That’s pretty cool, but there definitely couldn’t be microbes in our brains, the most protected area of our bodies, right?

A head-turning poster3 at the November 2018 Society for Neuroscience scientific conference called into question the assumption of the brain as a sterile, bacteria-free zone. A team of researchers from The University of Alabama in Birmingham (UAB), led by Professor Rosalinda Roberts, showed high-resolution microscope images of mouse and human brains that depicted bacteria happily residing in astrocytes, star-shaped brain cells that interact with and support neurons.

Given this result, the Roberts team dove deeper and used RNA sequencing to identify which types of bacteria were in human and mouse brains. Intriguingly, most of the bacteria were identified as Firmicutes, Proteobacteria, and Bacteroidetes – 3 phyla commonly found in the gut. Perhaps these bacteria traveled from the gut to the brain, climbing up nerves or traversing blood vessels?…

https://kellybroganmd.com/tantalizing-evidence-of-a-brain-microbiome/

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