Scientists track evolution of microbes on the skin’s surface

Amazing stuff!

"In a new study, researchers ... have discovered that this microbe can rapidly evolve within a single person’s microbiome. They found that in people with eczema, S. aureus tends to evolve to a variant with a mutation in a specific gene that helps it grow faster on the skin.
This study marks the first time that scientists have directly observed this kind of rapid evolution in a microbe associated with a complex skin disorder. ...
Using this technique, the researchers found that most patients maintained a single lineage of S. aureus — that is, it was very uncommon for a new strain to come in from the environment or another person and replace the existing S. aureus strain. However, within each lineage, a great deal of mutation and evolution occurred during the nine months of the study. ...
Many of these mutations arose in a gene called capD, which encodes an enzyme necessary for synthesizing the capsular polysaccharide — a coating that protects S. aureus from recognition by immune cells. In two out of six deeply sampled patients, cells with capD mutations took over the entire S. aureus skin microbiome population, the researchers found. ..."

From the highlights and abstract:

"Highlights

• Most patients are colonized stably by a single S. aureus sequence type

• Within each lineage, de novo variants spread and replace their on-person ancestors

• On-person and across-person parallel evolution is observed in capD

• Capsule loss enriched on AD patients compared with healthy carriage or other diseases

Summary

The opportunistic pathogen Staphylococcus aureus frequently colonizes the inflamed skin of people with atopic dermatitis (AD) and worsens disease severity by promoting skin damage. Here, we show, by longitudinally tracking 23 children treated for AD, that S. aureus adapts via de novo mutations during colonization. Each patient’s S. aureus population is dominated by a single lineage, with infrequent invasion by distant lineages. Mutations emerge within each lineage at rates similar to those of S. aureus in other contexts. Some variants spread across the body within months, with signatures of adaptive evolution. Most strikingly, mutations in capsule synthesis gene capD underwent parallel evolution in one patient and across-body sweeps in two patients. We confirm that capD negativity is more common in AD than in other contexts, via reanalysis of S. aureus genomes from 276 people. Together, these findings highlight the importance of the mutation level when dissecting the role of microbes in complex disease."

Scientists track evolution of microbes on the skin’s surface | MIT News | Massachusetts Institute of Technology A new analysis reveals how Staphylococcus aureus gains mutations that allow it to colonize eczema patches.

On-person adaptive evolution of Staphylococcus aureus during treatment for atopic dermatitis (open access)

Graphical abstract