F
or three decades, biologist
Rosalinda Roberts has cut ultra-
thin slices from the brains of the
recently deceased, studying
them closely under an electron
microscope. Originally she was searching for
the cause of schizophrenia, but over time
she became ever more obsessed with small
spots that ought not be there, yet existed in
several areas of the brain tissue. And when
Roberts finally realised what these spots
were in 2018, she was surprised.
They were bacteria, and the scientist
from the University of Alabama became the
first ever to prove that our brains harbour
lots of bacteria.
Bacteria in the brain have always made
doctors sound the alarm, as an infection in
the delicate brain tissue is associated with
lethal diseases such as meningitis. But
Roberts’ research indicates that lots of
bacteria exist permanently in the brain
without alerting the immune system or
causing infection. Quite the opposite. Thebacteria in the brain could prove to be indis-
pensable in controlling thoughts, improving
mental health, and even in protecting
against depression and Alzheimers’.Thinking with your gut bacteria
In Rosalinda Roberts’ experiment, slices of
34 healthy human brains were placed under
a powerful electron microscope. There the
electron bombardment showed the braintissue in great detail, revealing that the
strange oblong spots were the length of
microbes and were surrounded by a thick
wall that normally encapsulates the cell
structure of bacteria. Some of them were
linked in chains, in the way that bacteria
often are. The studies left no doubt: all the
brains harboured bacteria.
Subsequently, Rosalinda Roberts and her
colleagues identified the bacterium species
by studying the sequence of 16S rRNA genes
that are unique to all organisms. The brain
tissue included genes from several bacteria,
and a surprising 92% of the bacteria species
belonged to one of the three major classes of
bacteria that also make up the majority of
intestinal flora.Lactic acid flora calms mice
The intestinal bacteria’s beneficial effect on
the brain has been observed by scientists
since 2011, when neurologist John Cryan
from University College Cork in Ireland fed
lab mice bouillon mixed with a type ofMicrobes
that may
influence
your brain
92% of the bacteria that have
been discovered in human
brains belong to three major
bacteria classes: Bacteriodetes,
Proteobacteria, and Firmicutes.
These make up 68% of intestinal
flora, and are suspected to either
increase or reduce the risk of
brain diseases.34
healthy human brains
have been examined, and
each contained bacteria.BACTEROIDESVOLKER STEGER/SCIENCE PHOTO LIBRARY/CLAUS LUNAUSTEVE^GSCHMEISSNER/SCIENCE^ PHOTOLIBRARYSOUTHAMPTONGENERAL^ HOSPITAL/SCIENCE^PHOTO^LIBRARYKATERYNAKON/SCIENCEPHOTOLIBRARYHELICOBACTER PYLORILACTOBACILLUS62 | SCIENCE ILLUSTRATEDHUMANS BRAIN BACTERIA