Featured Research

from universities, journals, and other organizations

Women Have More Diverse Hand Bacteria Than Men

Date:
November 4, 2008
Source:
University of Colorado at Boulder
Summary:
A new study indicates that not only do human hands harbor far higher numbers of bacteria species than previously believed, women have a significantly greater diversity of microbes on their palms than men.

Women have a significantly greater diversity of microbes on their palms than men, a new study has found.
Credit: iStockphoto/Lisa Valder

A new University of Colorado at Boulder study indicates that not only do human hands harbor far higher numbers of bacteria species than previously believed, women have a significantly greater diversity of microbes on their palms than men.

The results have implications for better understanding human bacteria and should help establish a "healthy baseline" to detect microbial community differences on individuals that are associated with a wide variety of human diseases, said CU-Boulder Assistant Professor Noah Fierer, lead study author. A paper on the subject by the CU-Boulder researchers was published online Nov. 3 in the Proceedings of the National Academy of Sciences.

Using powerful gene sequencing techniques, the team found a typical hand in the new study had roughly 150 different species of bacteria living on it, said Fierer of CU-Boulder's ecology and evolutionary biology department. While the researchers detected and identified more than 4,700 different bacteria species across 102 human hands in the study, only five species were shared among all 51 participants.

"The sheer number of bacteria species detected on the hands of the study participants was a big surprise, and so was the greater diversity of bacteria we found on the hands of women," said Fierer. The study also showed that the diversity of bacteria on individual hands was not significantly affected by regular hand washing, he said.

The 332,000 gene sequences obtained by the CU team were nearly 100 times greater than those obtained from other studies of skin bacteria also obtained by sampling the entire DNA of microbe communities, known as "metagenomics." The new CU-Boulder study also confirms that standard skin culturing of human skin bacteria, a technique used by many labs, dramatically underestimates the full extent of microbial diversity, Fierer said.

Co-authors on the PNAS study included Micah Hamady of CU-Boulder's computer science department, Christian Lauber of CU-Boulder's Cooperative Institute for Research in Environmental Sciences and CU-Boulder chemistry and biochemistry Assistant Professor Rob Knight. The study was funded primarily by the National Institutes of Health and the National Science Foundation.

Fierer speculated that skin pH may play a role in the higher bacterial diversity on women's hands, since men generally have more acidic skin, and other research has shown microbes are less diverse in more acidic environments. The findings also could be due to differences in sweat and oil gland production between men and women, the frequency of moisturizer or cosmetics applications, skin thickness or hormone production, he said.

The right and left palms of the same individual shared an average of only 17 percent of the same bacteria types, said Knight. Study volunteers, all CU undergraduates, shared an average of only 13 percent of bacteria species with each other, he said.

Although the composition of bacterial communities on dominant and non-dominant hands of subjects was significantly different, diversity levels were similar, Fierer said. The differences found between dominant and non-dominant hands were likely due to environmental conditions like oil production, salinity, moisture or variable environmental surfaces touched by either hand of an individual, he said.

While some groups of bacteria were less abundant following hand washing, others were more abundant, said Knight, who stressed that regular hand washing with anti-bacterial soap is beneficial. "The vast majority of bacteria are non-pathogenic, and some bacteria even protect against the spread of pathogens," Knight said. "From a public health standpoint, regular hand washing has a very positive effect."

"Although hand washing altered community composition, overall levels of bacterial diversity were unrelated to the time since the last hand washing," wrote the researchers in PNAS. "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 CU-Boulder team used the metagenomic survey to simultaneously analyze all of the bacteria on a given palm surface, said Knight. In simple terms, the effort involved isolating and amplifying tiny bits of microbial DNA, then building complementary DNA strands with a high-powered sequencing machine that allowed the team to identify different families, genera and species of bacteria from the sample.

Knight recently received a $1.1 million NIH grant to develop new computational tools to better understand the composition and dynamics of microbial communities. He has been developing novel methods to tag DNA samples with error-correcting "barcodes" to obtain more accurate sequencing data.

The richness of bacteria types on the palm was three times higher than that found on the forearm and elbow, according to the researchers. The total diversity of hand bacteria appears to match or exceed levels of bacteria colonizing other parts of the body, including the esophagus, the mouth and lower intestine, Fierer said.

"I view humans as 'continents' of microscopic ecological zones with the kind of diversity comparable to deep oceans or tropical jungles," Fierer said. "Today we have the ability to answer large-scale questions about these complex microbial communities and their implications for human health that we weren't even asking six months or a year ago."


Story Source:

The above story is based on materials provided by University of Colorado at Boulder. Note: Materials may be edited for content and length.


Cite This Page:

University of Colorado at Boulder. "Women Have More Diverse Hand Bacteria Than Men." ScienceDaily. ScienceDaily, 4 November 2008. <www.sciencedaily.com/releases/2008/11/081103192310.htm>.
University of Colorado at Boulder. (2008, November 4). Women Have More Diverse Hand Bacteria Than Men. ScienceDaily. Retrieved August 29, 2014 from www.sciencedaily.com/releases/2008/11/081103192310.htm
University of Colorado at Boulder. "Women Have More Diverse Hand Bacteria Than Men." ScienceDaily. www.sciencedaily.com/releases/2008/11/081103192310.htm (accessed August 29, 2014).

Share This




More Plants & Animals News

Friday, August 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Huge Ancient Wine Cellar Found In Israel

Huge Ancient Wine Cellar Found In Israel

Newsy (Aug. 28, 2014) An international team uncovered a large ancient wine celler that likely belonged to a Cannonite ruler. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins