女性的手寄生更多细菌Women's Hands Home To More Bacteria

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Women's Hands Home To More Bacteria

Human being have far more different kinds of bacteria on the palms of their hands than previously thought and women's hands are home to a more diverse range than men's, said US researchers this week.

The study was the work of lead author Noah Fierer, Assistant Professor in the ecology and evolutionary biology department at the University of Colorado at Boulder (CU-Boulder) and colleagues, and is to be published this week in the Proceedings of the National Academy of Sciences, PNAS.

Fierer and colleagues said their findings increase our understanding about human bacteria and what constitutes a "healthy baseline" so that differences from this can be used to track disease.

For the study, Fierer and colleagues used powerful gene-sequencing methods to establish that the typical human hand was home to about 150 different species of bacteria although the number of different species they found on a total of 102 different hands came to more than 4,700 of which only 5 were common to all 51 participants, who were all CU undergraduates.

The method they used allowed them to analyze all the bacteria on the surface of a given palm. They isolated and amplified small pieces of bacterial DNA, then built complementary DNA strands with a high-powered sequencing machine so they could identify families, genera and species of bacteria.

Fierer said they were surprised by the "sheer number of bacteria species detected on the hands of the study participants" and by the "greater diversity of bacteria we found on the hands of women".

There were other surprising results. For example, the left and right hands on the same person differed significantly too. On average the right and left palms of the same person only shared about 17 per cent of the same species of bacteria.

In fact, the total diversity of bacteria present on human hands appears to be comparable to or even exceeds that known to exist in in other parts of the body, including the esophagus, the mouth and lower intestine said Fierer.

The investigators found 332,000 gene sequences altogether, some 100 times more than the number discovered by other studies of skin bacteria.

Fierer said the study also confirmed that the standard method of culturing used by many labs to find bacteria on human skin dramatically understimates the full range of microbial diversity.

Skin pH differences between men and women's skin may explain why women's hands carry a wider range of bacteria said Fierer: men's skin tends to be more acidic and other studies have shown that bacteria don't survive so well in acidic environments.

Other reasons could be gender differences in skin thickness, hormones, sweat and oil gland secretion, and use of skin products like moisturizers, they said.

The differences between right and left palms could be because of dominant and non-dominant hand effects which affect oil production, salinity and moisture on the palms, as well as the effect of touching different surfaces with different hands, said the researchers.

The study also showed that the range of species was not affected by regular hand washing.

Fierer and colleagues found that as expected, levels of some bacteria went down after hand washing, but unexpectedly, others went up. They stressed the importance of washing with anti-bacterial soap.

"The vast majority of bacteria are non-pathogenic, and some bacteria even protect against the spread of pathogens," said co-author Rob Knight, who is Assistant Professor of chemistry and biochemistry at CU-Boulder.

"From a public health standpoint, regular hand washing has a very positive effect," he added.

Fierer and colleagues wrote that although hand washing changed the bacteria composition, the overall diversity of bacteria found on the participants' hands was not related to how long their hands went unwashed. They speculated that:

"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 also found that compared to that found on nearby regions of the body like the forearm and elbow, the palm of the hand was home to three times the range of bacteria.

Fierer said he saw human bodies as "continents of microscopic ecological zones" harbouring diverse ecosystems comparable to deep oceans or tropical jungles.

"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," he added.

The other authors of the paper were Micah Hamady of CU-Boulder's computer science department and Christian Lauber of CU-Boulder's Cooperative Institute for Research in Environmental Sciences.
女性的手寄生更多细菌

美国学者本周指出，人类手掌上存在的细菌种类比我们原来想象的要多得多，而且女性手部的细菌种类要远多于男性。

这项研究由美国科罗拉多大学生态学学进化生物学系助理教授领导，相关论文将在本周发表于美国《国家科学院院刊》（PNAS）上。

Fierer及其同事认为，这项研究有助于我们更好的理解人体细菌，人体细菌的个体差异可以帮助我们诊断多种疾病。

在此项研究中，Fierer及其同事使用先进的基因序列分析技术，分析了51名科罗拉多大学的大学生手上的细菌，虽然在102只手上共确认超过4700种细菌，一只手上大约有150种细菌，却只有5种细菌在这51人手上共同被检测到。

他们用的这种方法可以分析手掌表面的所有细菌。他们分离并扩增细菌DNA的小片段，然后用先进的测序仪合成了互补的DNA双链以便于分析细菌的种属。

Fierer表示，在研究对象手上检测到的细菌种类数和在女性手部发现的细菌的复杂的多样性，令他们感到吃惊。

还有其他令人吃惊的结果。例如，即使是同一个人的左右手也有很大差别。同一个人的左手掌和右手掌平均仅有17%的细菌种类是相同的。

Fierer说，事实上，人类手部的细菌多样性可与身体其他部位存在的细菌种类相比，或者超过其他部位，包括食道、口腔和小肠。

研究小组获得了332000个基因序列，几乎是其它皮肤细菌研究所得数目的100倍。

Fierer说，这项研究证明许多实验室所使用的人类皮肤细菌的标准培养技术明显低估了微生物的多样性。

Fierer猜测女性手部细菌种类多于男性这一现象是由于男性与女性皮肤的PH值不同，因为男性皮肤更偏酸性，而其他研究表明在这样的酸性环境下，细菌不能很好的生存。

他们认为，造成这一现象的其他原因可能是男女皮肤厚度、荷尔蒙、汗腺和皮脂腺的差异以及使用护肤品（像保湿剂）的差异。

研究者认为，惯用手和非惯用手影响手掌出油量、含盐量和湿度，这是左手与右手的细菌种类数差异的一个原因。同样，不同的手触摸不同的表面，也是造成差异的一个原因。

研究表明勤洗手并不能影响每个人手部细菌种类的多少。

Fierer及其同事发现，正如预期所想，洗手后一些细菌群减少，但是出乎意料的是，另外一些细菌群增加。他们强调用抗菌皂洗手的重要性。

论文合著者Rob Knight是科罗拉多大学化学和生物化学助理教授，他说“大多数细菌是非致病性的，一些细菌甚至保护人体、阻止病原体传播”。

他补充说，“从公共卫生角度来看，勤洗手有非常好的效果。”

Fierer及其同事写道，虽然洗手可以改变细菌组分，但是在参与者手部发现的细菌种类多少与不洗手时间长短不相关。他们推测“可能是因为洗手后细菌菌落又迅速形成或者是洗手时（此次研究中的学生均是熟练的洗手）没有洗去皮肤表面的大部分细菌”

研究者还发现手掌的细菌种类数是其附近区域的三倍，比如前臂和肘部。

Fierer认为，与深海或者是热带丛林相比，人类身体可以看做是“大陆的微观生态区”，是不同生态系统的港湾。

他还说，“现在我们有能力回答有关微生物群落的复杂性和他们对人类健康的潜在意义的问题，在一年前，甚至六个月前，这些问题是不会被问及的。”

论文的其他作者是科罗拉多大学计算机科学系的Micah Hamady和科罗拉多大学环境科学研究合作学院的Christian Lauber。
摘自丁香园

美罗

谢分享！平时监测也出现这种现象，个别人的手每次采样均超标（洗后采样）；还有，同一块肥皂你洗有泡末产生，他洗就没有泡末，看来这就叫个体差异吧。:o

老朽

后甚有感悟，值得思考。谢谢你的转载。

桂花香

洗手后一些细菌群减少，但是出乎意料的是，另外一些细菌群增加。”
看来我们要更积极反思过去常做的洗手监测了。

xiaolongnv

女性的手寄生更多细菌":o
是女人太勤劳了的缘故吧;P

潮水

化妆品用多了,呵呵!