Feet are a great site of fungal and bacterial diversity. "Sometimes, though, in particularly warm and moist areas, they grow a bit overexuberantly and cause problems," writes Stephanie Swift at mmmbitesizescience. "Athlete's foot and toenail infections are two common examples of fungi gone wild."
Researchers at the US National Institutes of Health report in Nature on the foot fungal diversity of 10 healthy volunteers using both culture- and DNA-based approaches. From this, Julie Segre and her colleagues found that the plantar heels, toenails, and toe webs were the areas of the greatest diversity. However, a number of the healthy volunteers — about 20 percent — appeared to have scaling or other changes indicative of underlying fungal infections.
Further, they note that foot fungal diversity has low stability, and it and bacterial diversity are not linearly correlated.
"This suggests that the normal exposure of the foot to the outside world causes constant shifts in microbial ecosystems that present opportunities for pathogenic fungi to become established," Swift adds.