The
healthy lung receives microbes from the mouth, a new model suggests.
The
small community of bacteria that make up the lung microbiome isn’t particularly
suited for the harsh environment, but rather reflects the composition of microbial
species that live in the oral cavity and reach the lung via air flow, according
to a study published in mBio.
Microbiome
communities arise either by being selected for their adaptations to a
particular environment or by drifting over to a new environment from a
neighbouring one, a process known as neutral distribution. Since the lung
microbiome is both relatively small—with typically 1,000-fold less microbial
DNA than the amount isolated from the mouth—and well-connected to other
microbial communities throughout the respiratory tract, a team led by
scientists at the University of Michigan hypothesized that most of the bacteria
residing in the lungs came from elsewhere. To test their idea, the scientists
built a model of what the lung microbiome would look like if it were mainly
made up of bacteria entering from the oral cavity and compared the model
results to the actual microbial DNA composition of the lungs. The bacterial DNA
they found in healthy lungs largely matched the pattern that would be expected
from neutral distribution.
By
contrast, the researchers found that in lung samples from patients with cystic
fibrosis or pneumonia, the microbial populations did not fit the neutral
distribution model, indicating that diseased lungs do put selective pressure on
their microbial residents.
Posted by Tim Sandle
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