There are more bacterial cells than human, on and inside the average human being. The average is one million bacteria per square centimeter of your inner elbow, washed or not.
Commensal bacteria serve a useful purpose. The ones on your inner elbow, which is so exotic it has six separate tribes of bacteria, convert fats in the area, moisturizing it, according to a current study by the National Human Genome Research Institute.
So in theory you could moisturize yourself by wiping your inner elbow and then wiping your face.
You can almost hear the support groups forming, can’t you?
The no doubt fertile and duly moistened New York Times
Dr. (Julia A.) Segre and colleagues report their discovery of the six tribes in a paper being published online on Friday in Genome Research. The research is part of the human microbiome project, microbiome meaning the entourage of all microbes that live in people.
The project is an ambitious government-financed endeavor to catalog the typical bacterial colonies that inhabit each niche in the human ecosystem.
The project is in its early stages but has already established that the bacteria in the human microbiome collectively possess at least 100 times as many genes as the mere 20,000 or so in the human genome.
Since humans depend on their microbiome for various essential services, including digestion, a person should really be considered a superorganism, microbiologists assert, consisting of his or her own cells and those of all the commensal bacteria. The bacterial cells also outnumber human cells by 10 to 1, meaning that if cells could vote, people would be a minority in their own body.
In other words, you’re a planet, more or less. They haven’t even started on the mites that live on people, or the fungi… Do it right, and you could rate your own wildlife documentary. If David Attenborough shows up at your house, you’ve hit the jackpot.
You could probably make your own brand of beer and wine, too. Ask your tinea or Candida (thrush) for details… and recipes.
Or not. The commensals are pretty tough customers, and not recommended dietary supplements.
It was known that people were covered in bacteria, but this research has taken some time to turn into proven fact. Another issue that the project is supposed to address is finding out how pathogenic bacteria are able to take over and cause disease.
One thing that the research has discovered is that babies’ original gut bacteria come from their mothers.
This new view of people as superorganisms has emerged from the cheap methods of decoding DNA that are now available. Previously it was hard to study bacteria without growing them up into large colonies. But most bacteria are difficult to culture, so microbiologists could see only a small fraction of those present. Analyzing the total DNA in a microbial community sidesteps this problem and samples the genes of all bacterial species that are present.
This microbial profile is called a “microbiome”.
Not mentioned is the fact that the same bacteria are easily cultured on people. Anyone looking for a job as an agar plate may be in luck.
On the other hand you could be recruited as an agar plate and evolved into a sort of bacteria factory.You could find squads from Maybelline hanging around.
Antibiotics are a problem for the commensals, and the ecology can get knocked around:
Taking a broad spectrum antibiotic presumably wreaks devastation on one’s companion microbiome. If the microbiome is essential to survival, it is perhaps surprising that the drugs do not make more people ill. Dr. Relman said that perhaps there were subtle long-term consequences that had not yet been identified. Much the same set of bacteria recolonize the gut after a course of antibiotics, he said, suggesting that the makeup of the colony is important and that the body has ways of reconstituting it as before.
Actually, there’s another possibility or two.
Humans are social animals, and external bacteria are released into the environment by skin flakes. People shed millions of skin flakes a day. That one million per square centimeter would do as a starter population.
Gut flora is endemic to the human being, and the natural habitat for those bacteria. They exist in huge populations, and antibiotics aren’t likely to wipe them out entirely.