According to a new study by University of Colorado researchers, women hands carrying far more germs than men's. The study published online Monday in the Proceedings of the National Academies of Science, said this information could help scientists work out what constitutes a "healthy" level of bacteria, diagnose disease and maybe even get an advance warning of something about to go amiss.

Robert E. Marquis, a professor of microbiology and immunology at the University of Rochester Medical Center said, "The findings of the last few decades suggest that many diseases are due to many organisms, and it's the concerted change that leads to disease,"

Researchers in the study swabbed 102 human palms of 51 undergraduate students for bacteria, just after the students had finished their academic exams and found more than 4,700 species of bacteria. A sampling of the entire DNA of microbes (known as metagenomics) showed 332,000 gene sequences, about 100 times more than was found in earlier studies. Noah Fierer, assistant professor of ecology and evolutionary biology and the paper’s lead author said,    "Bacteria are tough to identify. Most of them can’t be grown in the lab. The best way we have of identifying them is to look for their DNA." The species varied from person to person and just five were shared among all of the volunteers with an average of 150 different species of bacteria found on each hand. An interesting finding was that both hands bacteria differed, an individual’s right had different species than the left.

Microbes are relatively unknown and the National Institutes of Health has initiated the Human Microbiome Project, with the objective of mapping human microbiota. "With all the bacteria in the world, we probably know of less than 1 percent of them," Marquis said. He added that the technology used in the study will help scientists encounter the other 99 %.

Fierer said, not all bacteria are harmful most are neutral and some may even protect the skin from pathogenic varieties.  He added that why women have more bacteria on their hands was not clear it could be that men’s more acidic skin discourages some species, or that sweat, hormones or women’s greater use of hand creams play a role. "The findings don’t necessarily mean that women have more germs than men, just more variety," he said.

Washing hands reduces the abundance but not the variety of microbes.  "We’re not saying at all that washing hands is not a good idea," Fierer said. "We know that it reduces abundance and has a large effect on pathogens."

The study was funded by the National Institutes of Health and the National Science Foundation.