Bacterial microbiomes on human skin

Nearly a year ago, I shared results of a study of the bacteria that live on human skin, including these fun facts:

• Females have a higher diversity of bacteria on their hands than males . . . perhaps due to a slightly higher skin pH in women, or perhaps the mix of sebum, sweat, and lotions, or maybe even hormonal differences . . . they couldn't really say for sure at this point

• Females have more bacteria living under the surface film of skin than males

• 4, 742 different species of bacteria were found in the whole group of subjects

• The species each of has on our hands is a rather unique mix--only 5 (out of 4,742) species were found on every hand in the group

• Most of the 150 or so different species of bacteria found on skin of an individual hand are beneficial or harmless . . . only a small minority are pathogenic

• The diversity of bacteria differs between a person's right hand and left hand

• Hand washing (as practiced in this group) did not remove many of the bacteria (or the populations recovered rapidly after washing)

Recently, another study was published that gives us an even more complete picture of the micro-ecology of human skin.  The report, published online a few days ago by the journal Science, provides an inventory of what organisms live where on the human skin.

A few fun facts about the bacteria, viruses, and fungi of the human skin gleaned from the new study:

• Microbes on the skin outnumber human cells by at least 10 times (about 100 trillion microbial symbionts)
  
  
• Microbial community composition is determined primarily by habitat (well, of course!)
  
  
• The composition of microbial communities varies widely from one person to another
  
  
• The compostion of microbial communities for an individual human do not vary much over time
  
  
• Some locations of the skin harbor more diverse communities than even the mouth or gut

Want to know more?

Bacterial Community Variation in Human Body Habitats Across Space and Time.
Elizabeth K. Costello, et al. 
Science Express, 5 November 2009, online .
doi: 10.1126/science.1177486
[Recent study on human flora]

Bacteria Flourish in Favorite Ecosystems on the Human Body
Laura Sanders
Science News November 5, 2009
[Nice summary of the study's importance and implications]

Variation In Bacterial Populations From Person To Person Surprises Researchers
C. Paddock
Medical News Today 6 November 2009
[Press release about the new study]

Skin Ecology
K. Patton
The A&P Professor 18 November 2008
[My previous article on the topic.  Includes links to other articles.]