Women's hands boast more bugs
Ladies, your hands are a zoo. Sampling the DNA on human skin has revealed that while women's hands get washed more often than men's, they teem with a more diverse selection of bacteria.
Noah Fierer and colleagues at the University of Colorado at Boulder swabbed the palms of 51 students leaving an exam. When they amplified and sequenced the DNA, they found 4742 species of bacteria in total - nearly 100 times as many as previously seen. On average, each student carried 150 distinct species and 3200 different strains. Women had different bacteria and a greater number of species than men (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0807920105).
When the team tracked the bacterial composition of eight people's hands after they had been washed, they found that some bacteria preferred clean hands, while others appeared later. Men always had fewer species, though. The researchers suspect this is because men's skin is more acidic, as in nature acidic environments have less microbial diversity.
Surprisingly, every hand was very different. Only five species were found on all hands, while any two hands - even from the same person - shared just 13 per cent of species. Fierer says it may be possible to tell from the bacteria on an object which individuals have touched it.
Apart from the observation that men's skin is more acidic that women's (I can't even see why this is; must be something to do with hormones, I guess) it is hard to see what might cause this. Basic hygiene is clearly not the answer. Go figure!