Skin Flora:the accidental pathogen, the golden globe, and pink swans


Staphylococcus epidermidis (left), Kocuria rhizophila (middle) and Kocuria rosea (right)


Here are some new additions to C-MOULD, a unique culture collection specifically for microorganisms for use in art and design. 

Staphylococcus epidermidis: the accidental pathogen (left) is a very close friend of Staphylococcus aureus and MRSA. Whilst it isn’t as pathogenic as these bacteria has is a very important opportunistic pathogen, not able to cause illness in otherwise healthy people, but capable of infecting the compromised human host. In fact, it is now the most frequent cause of nosocomial infections, at a rate almost as high as that due S. aureus, its more virulent cousin Staphylococcus.  It also the most frequently isolated bacterium from human skin and is especially common in damp areas like the groin and arm pits. Skin is a surprisingly harsh environment for bacteria, and analysis of the S. epidermidis genome shows that this bacterium is well equipped with mechanisms that protect it here, and especially, allow it to tolerate extremes of salt concentration in the form of dried human sweat.

Kocuria rhizophila, formerly known as Micrococcus luteus (middle): sunscreens and the golden globe is also another common human skin inhabitant and is another bacterium that has adapted to be able to survive in this harsh environment. Like human skin is, bacteria are susceptible to the damaging effects of Ultraviolet Light (UV) and so K. rhizophilia synthesises a pigment that absorbs wavelengths of light from 350 to 475 nm. These wavelengths of UV, commonly referred to as UVA, have been correlated with an increased incidence of skin cancer, and it is possible that this pigment could be used to make a sunscreen that can protect humans against UVA. K. rhizophilia is also an important bacterium in the context of the history of microbiology and medicine, as it played a key role in Alexander Fleming’s discovery of lysozyme, to which it shows exquisite sensitivity (Fleming, 1922a,b). In fact, it is readily killed by the lysozyme present in human tears irrespective whether they are generated by happiness or grief. Finally, variants of K. rhizophila can precipitate gold by concentrating and crystallizing it on their surface.

Kocuria rosea: fake tans and pink swans: again is a commonly isolated bacterium from human skin. Its adaptation to this environment is its ability to breakdown and thus utilise keratin, the key structural protein making up the outer layer of human skin. The name of the species rosea, gives a clue to the colour of its colonies which are pink. It also produces a variety of different pigments one of which is canthaxanthin. This is a rust coloured pigment that is approved as a food additive in a number of countries. It is also the active component of tanning pills. When taken at these large doses, many times greater than the amount normally ingested in food, this substance is deposited in various parts of the body, including the skin, where it imparts a golden orange hue, because it accumulates in the  panniculus. However, when consumed in these high doses it causes canthaxanthin retinopathy, which can lead to loss of vision, because the pigment accumulates in the macular (the central part of the retina). Finally, by virtue of its colour and keratin digesting activity K. rosea may also be involved in a mysterious condition in swans called Pink Feather Syndrome, in which the birds develop a pink coloration on their feathers.  Overtime, the pink feathers become degraded, and the swans may die.












Leave a Reply