The original version of this story appeared in Quanta Magazine.

Bacteria are present everywhere, from the depths of the ocean to the human body. While it has been believed that bacteria cannot survive in the human brain due to the blood-brain barrier, recent research suggests otherwise. Studies have shown conflicting evidence over the years, mainly due to the challenges of obtaining uncontaminated brain tissue for analysis.

A recent study published in Science Advances has provided compelling evidence that a brain microbiome exists in healthy vertebrates, specifically fish. Researchers at the University of New Mexico found communities of bacteria thriving in the brains of salmon and trout, some with unique adaptations to survive in brain tissue and cross the protective blood-brain barrier.

Matthew Olm, a human microbiome expert at the University of Colorado, Boulder, expressed skepticism initially but found the new research convincing. This discovery raises questions about the existence of a brain microbiome in humans and other mammals.

Researcher Irene Salinas, who studies fish immune systems, led the investigation into fish brain microbiomes. The study revealed that fish brains host a variety of bacteria, challenging the long-held belief that the blood-brain barrier prevents microbial colonization.

Salinas and her team meticulously studied the fish’s brain tissue to confirm the presence of living microbes, suggesting that these bacteria may have colonized the brain during early development. The study, conducted over five years, provided strong evidence for the existence of a brain microbiome in vertebrates.

These findings raise intriguing questions about the role of microbes in neurobiology and the potential impact on human health.

The study sheds light on the potential presence of a brain microbiome in vertebrates and its implications for human health.

Fishing for microbes

Irene Salinas, an evolutionary immunologist at the University of New Mexico, led the groundbreaking research on fish brain microbiomes. Her team’s findings challenge existing beliefs about the blood-brain barrier and microbial colonization in the brain.

By examining the olfactory bulbs of trout and salmon, Salinas and her team identified a diverse range of bacteria in the fish brains, indicating the presence of a brain microbiome. The study, conducted over five years, provided compelling evidence for the existence of living microbes in fish brains.

Further research is needed to understand how these bacteria colonize the brain and their potential impact on neurobiology. The study opens up new avenues for exploring the role of microbes in brain health and function.