Bacteria from a human beard. Coloured scanning electron micrograph (SEM) of bacteria cultured from a human beard. A European study has found that the average man's beard is more replete with human-pathogenic bacteria than the dirtiest part of a dog's fur. There are around 1000 species of bacteria from 19 phyla found on human skin. Skin flora is usually non-pathogenic, and either commensal (not harmful to their host) or mutualistic (offer a benefit). Magnification: x4000 when printed at 10cm wide.