Monday, 4 January 2016

We’re Each Surrounded By A Microbial Cloud

Microbial cloud
We not only carry microorganisms across our skin, as well as playing host to a complex arrangement of microorganisms within our bodies (the collective microbiome), we also carry out own ‘cloud’ of bacteria and fungi with us as we sit or walk about. At least this is the inference of a new report from microbiologists based at the University of Oregon. The number of bacteria, relative to our own cells, out-number body cells by 10 to 1.

The cloud (or more exactly the bioaerosol) is made up of resident and transient bacteria found on the skin that are shed through the loss of skin cells, together with the microorganisms that are expelled from the lungs. Over the course of an hour the typical person will emit around one million ‘biological particles.’Most microorganisms in the air are not found free-floating; rather they are attached to rafts of matter, like skin flakes and dust.

The interesting thing that the research suggests that every time you get close to another person, the other person’s own microbial cloud ‘rains’ upon you, depositing some microbes on your skin and you will also breathe in many as well.

The cloud generation and associated mixing was shown by placing subjects in special chambers for periods of four hours. The air was filtered using high efficiency particulate air filters (HEPA), which meant that the air collected and analyzed contained microorganisms generated by the subjects only. The use of chambers were necessary to differentiate human generated aerosols compared with those in the natural or man-made environment.

The key revelation was that each person’s microbial cloud was unique. Speaking with BBC Science, Dr. James Meadow, who was involved with the study, stated:
 “We expected that we would be able to detect the human microbiome in the air around a person, but we were surprised to find that we could identify most of the occupants just by sampling their microbial cloud."
The types of bacteria isolated were those associated with human skin, such asStaphylococcus epidermidis and Corynebacterium jeikeium. There were also bacteria associated with the clinical setting, such as Peptoniphilus ivorii; those commonly found in the lungs, Anaerococcus prevotii; and those linked with the sinuses, including Corynebacterium tuberculostearicum. Whilst types of bacteria were similar, clear genetic differences could be discerned between people and this allowed the phenomenon of some bacteria from one person’s cloud being, to different levels, deposited on another person.

The study, while interesting, was based on a small sample of 11 people. Each of the subjects had been given a clean bill of health prior to the study starting and they had not taken antibiotics within four months of the study starting. The findings, supported by genetic level analysis (assessment of 16S rRNA genes), are published in the journal Peer J. The research paper is titled “Humans differ in their personal microbial cloud.”

Posted by Dr. Tim Sandle