This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The human body is teeming with more than 35 trillion bacteria, coexisting in microbiomes inside the gut, mouth, lungs, skin and urogenital tract. While it's now clear these microbes are associated with health and disease, scientists have only begun to uncover the full scale of their biology and functions.
In a striking example of just how much is still unknown, a new University of Michigan study overturns a 100-year-old assumption about one common bacterial resident of the lungs, Prevotella melaninogenica. The research is published in the Journal of Bacteriology. The lab led by Ariangela Kozik, Ph.D., assistant professor of internal medicine at U-M Medical School and assistant professor of molecular, cellular and developmental biology at U-M, is interested in Prevotella because the bacteria are commonly found in the respiratory tract and reportedly associated with all manner of chronic conditions, yet are also found in healthy people.
The genus is also widely thought to be an obligate anaerobe, incapable of surviving in the presence of oxygen. What, they wondered, is it doing in the lungs? Kozik, an asthma researcher, notes that Prevotella are found in differing amounts inside the respiratory tract in both healthy people and people with asthma and COPD, accounting for roughly 10% of microbial populations in healthy lungs and up to 13%, on average, among individuals with respiratory disease.
To unravel this paradox, Kozik's team subjected cultures of P. melaninogenica to increasing percentages of oxygen, comparing the rates of growth and survival. They found that the upper threshold for growth was between 5–8% oxygen, and the bacteria could briefly survive oxygen levels as high as 21%. Furthermore, the study found, using a new real-time sensor platform and RNA sequencing, that Prevotella appear to be consuming oxygen and dealing with oxidative stress and DNA damage differently than other aerobic bacteria.
"Prevotella has all of these mechanisms to allow it to survive in oxygenated environments that previously were not appreciated for this organism at all, changing what we thought we knew," said Kozik. The ability to exist in the presence of oxygen may lie along a spectrum and not be as clear-cut as scientists have traditionally defined, she notes. Kozik and her lab hope to next interrogate how the immune system responds to Prevotella and dive deeper into lung bacteriology to understand specifically how these microbes affect the body.
"We need to work to look at the bacterial community and ask, how does this community currently function? What metabolites are they making, what signals are they sending to the immune system? How's the immune system responding to it?
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