Your hands are an ecosystem

Neat. A little gross, but still neat. [Link]

The researchers took samples from the palms of 51 college students — that's 102 hands — and tested the samples using a new, highly detailed system for detecting bacteria DNA.

They identified 4,742 species of bacteria overall, only 5 of which were on every hand, they report on Monday's online edition of Proceedings of the National Academy of Sciences.

The average hand harbored 150 species of bacteria.

Not only did individuals have few types of bacteria in common, the left and right hands of the same individual shared only about 17 percent of the same bacteria types, the researchers found.

The differences between dominant and non-dominant hands were probably due to environmental conditions like oil production, salinity, moisture or variable environmental surfaces touched by either hand of an individual, Fierer said.

Knight said the researchers hope to repeat the experiment in other countries where different hands are assigned specific tasks.

While the researchers stressed the importance of regular hand washing, they also noted that washing did not eliminate bacteria.

"Either the bacterial colonies rapidly re-establish after hand washing, or washing (as practiced by the students included in this study) does not remove the majority of bacteria taxa found on the skin surface," the researchers said in their report.

While the tests could determine how many different types of bacteria were present, they could not count the total amount of bacteria on each hand.