Chapter 1: The Fascinating Discovery

During the annual Society for Neuroscience meeting in 2018, a poster presentation captivated many researchers with its astonishing images of bacterial cells residing within human brain cells. "This is the talk of the conference," remarked Ronald McGregor, a neuroscientist from UCLA, who was not associated with the presentation. "It's like uncovering an entirely new molecular factory in the brain..."

Initially, Rosalinda Roberts, a neuroanatomist from the University of Alabama at Birmingham, and her team were examining preserved brain tissues from individuals with schizophrenia and comparing them to those without the condition. Using electron microscopy, they captured detailed images of these brain tissues.

It was Courtney Walker, an undergraduate in Roberts' lab, who noticed rod-shaped entities in the images. Although Roberts had previously observed these shapes, she had dismissed them as she was focused on different aspects. "I would see them and think, 'Oh, here are those things again,'" she recalled. There was also a possibility that these observations stemmed from contamination during the brain extraction process.

Encouraged by Walker, Roberts consulted with bacteriologists, who confirmed that these rod-like structures were indeed bacteria—34 bacterial cells identified in total across both types of brains. The bacteria were predominantly found within the neuronal myelin sheath and the blood-brain barrier, areas rich in fat and sugar. Roberts speculated that these bacteria might have been drawn to these nutrient-rich brain regions, while Walker theorized that they may have originated from the gut, leaking into the brain upon the individual's last breath.