What is already known on this topic
Cutibacterium acnes is the main microbe found on the oily skin of the face and back of healthy adults. Because the microbe resides in body sites that differ in oxygen concentration, nutrient availability, and exposure to the environment, scientists have hypothesized that different C. acnes strains occupy different niches.
What this research adds
By analyzing C. acnes strains collected from healthy people, researchers found that each person had a unique combination of strains on their skin, but individual skin pores are dominated by specific bacterial strains, which are different from those of neighboring pores. That’s likely because the pore anatomy and physiology make it hard for a bacterium to descend into the pore, so the bacteria that reach the depths of the pore can rapidly expand and block new colonizers.
Conclusions
The findings may explain why bacterial strains on the skin are stable over time, despite the skin’s exposure to the environment. They also suggest that, in order to manipulate the human microbiotas to help treat disease, scientists have to gather information not only about the identities of microbes but also about their location and arrangement in different body sites.
Thousands of types of bacteria inhabit the human skin, but skin pores contain only one type of microbes. That’s according to new research that looked at the varieties of Cutibacterium acnes on the skin of healthy people.
The findings, published in Cell Host & Microbe, may explain why bacterial strains on the skin are stable over time, despite the skin’s exposure to the environment. They also suggest that, in order to manipulate the human microbiotas to help treat disease, scientists have to gather information not only about the identities of microbes but also about their location and arrangement in different body sites.
C. acnes is the main microbe found on the oily skin of the face and back of healthy adults. Because the microbe resides in body sites that differ in oxygen concentration, nutrient availability, and exposure to the environment, scientists have hypothesized that different C. acnes strains occupy different niches.
To test this hypothesis, Tami Lieberman at the Massachusetts Institute of Technology and her colleagues analyzing C. acnes strains collected from the forehead, cheeks, and back of 16 healthy people.
Pore diversity
The researchers grouped bacterial colonies into lineages and found that a typical person has multiple lineages, including some from the same strain type, on their skin. None of the lineages was specific to particular body regions, such as the forehead and the back. Instead, all strains appeared to be able to colonize pores and live on any oily skin region.
Although each person had a unique combination of C. acnes strains on their skin, individual skin pores were dominated by specific bacterial strains, the team found. Each pore was different from neighboring ones: for example, three pores within a one-centimeter patch of skin each harbored three different lineages of C. acnes.
Further analyses showed that colonies from a pore shared nearly identical genomes. This suggests that each pore contains clones of a single bacterial cell, which appeared to have colonized the pores about a year earlier.
Anatomy bottlenecks
The results led the researchers to propose that pore anatomy and physiology make it hard for a bacterium to descend into the pore. “C. acnes cells likely cannot proliferate rapidly until they reach lower depths in the pore, where the environment is anaerobic and nutrient rich due to sebum production,” the authors say. “In this way, pore physiology could enable a lucky single cell to establish a pore’s resident population, with abundant growth at the bottom of the pore blocking new migrants.”
The findings could also influence the design of microbial-based treatments for the skin and other tissues, the researchers say. “Understanding how host anatomy and physiology influence strain-level composition in microbiomes is critical to the design of precision microbiome therapeutics.”
The study highlights that the chance of a probiotic to colonize oily skin may depend on the efficient removal of the existing microbial community before treatment, the authors say.
