It is unsurprising that Frank Zappa referred to both zits and microbiology in his lyrics; his chronicling of the sociology of rock touring and fascination with social taboos made it inevitable; who else could have rhymed ‘maracas’ with ‘gonococcus’ in the classic Why Does It Hurt When I Pee?

♫ I want a brazen little Jewish Princess / With titanic tits and sandblasted zits

Anyway, there have been molluscs and fish named in his honour but microbiology has finally repaid the debt. Propionibacterium acnes is familiar to us all as one of the main zit-causing bacteria. A normal member of the rainforest of Microbial Overlords that inhabit us, it lives in hair follicles where it can hide from antibiotics and whatever else we throw at it.

It can cause catheter infections too but its association with hair and skin means it often appears in post-op infections. But it’s also one of the most indolent bugs around; an infection might take many years after surgery to manifest itself. And when P. acnes is debrided surgically the pus looks like scrambled eggs. Mmmmmm!

P. acnes Zappae


© 1977 Mark Estabrook

A group of Italian microbial geneticists recently published a rather interesting paper in Molecular Biology and Evolution showing that a formerly unknown P. acnes transferred to vine bark and pith some 7,000 years ago. They traced the evolutionary history of this P. acnes type Zappae by using two marker genes which show a human origin for the bacterium jumping over to the plant.

By analysing the ribosomal DNA from the stems of plants sampled from multiple sites throughout north east Italy they have been able to pin down the emergence of this strain to around 7,000 years ago – so it coincides with the first domestication of the grapevine. This temporal and genetic evidence means it is not a huge leap to propose that the grafting and pruning of vines may have led to P. acnes making this jump. It’s also interesting that one of these genes is a protein essential for the repair of DNA which P. acnes Zappae has now lost so it must rely on its vine host for survival. So far as I can tell this is the first evidence of human to plant obligate transfer. And named after Frank. How cool is that?

I wonder if the entomologists will take note of Zappa’s term for Pthirus pubis (aka ‘crabs’) and work it into their own taxonomy? I’ve never thought they look much like crabs (the lice that is, not entomologists); anyway, I think Zappa’s Toads of the Short Forest is far more descriptive.