In the same way that some of the bacteria on this list can actually be beneficial to digestive health, yeast also serves important functions. Namely, it's used to make pizza and beer. Yes, it is safe to say that the world is a better place with yeast in it. But that doesn't mean you want your phone caked in it.
The same Turkish study mentioned earlier found yeasts on about 1.5 percent of the phones tested [source: Ulger et al.]. Yeast is a fungus that can live almost anywhere on your body. Yeast infections cause immense itching on your skin or vagina and in the case of the vagina, a discharge as well [source: National Library of Medicine]. The good news is that you're unlikely to contract a yeast infection from your mobile device. Unless, that is, you're doing some pretty strange things with your phone.