Repopulation with green photosynthetic bacteria after exposure to light (1 week)

Original dark generated numbers/letters

Repopulation with green photosynthetic bacteria after exposure to light (1 week)

Original dark generated numbers/letters

Original dark generated numbers/letters

Repopulation with green photosynthetic bacteria after exposure to light (1 week)

The mask, a simple equation for photosynthesis.

The Winogradsky column is a simple device for culturing environmental bacteria and is an elegant means of demonstrating their vast diversity and complex interactions. Invented in the 1880s by Sergei Winogradsky, the device comprises, a column of pond mud that has been fortified with a carbon source and a sulphur source. The column is exposed to sunlight for a period of months to years, during which aerobic/anaerobic, and sulphur gradients form. All of the bacteria in the mud column are present initially in low numbers and are thus not visible to the human eye. However, during the incubation, different types of microorganism will come to occupy distinct zones where the oxygen and sulphur gradients generate specific environmental conditions, and niches, that favour their particular growth requirements and specific activities. In these zones, particular bacteria proliferate massively to form visible and brightly coloured communities.

Here I intervened by differentially exposing a Winogradsky column to light. This influenced where the specific types of bacteria were able to grow, resulting an image being generated by and recorded in the vast bacterial community. 3 months exposure.

After the mask has been removed to reveal the image, and as the bacteria are exposed to uniform light once more, the figures change as they become repopulated by green photosynthetic and other bacteria. In a sense, I see this as a type of alternative photography where the emulsion is a massively complex microbial community that responds to light. The ecology is perpetual and continually changing in response to its environment so the image never becomes permanent or fixed, but even if it disappears completely its legacy is preserved in the changes and influences that it made to the ecology.

I’ve worked with the remarkable slime mould Physarum polycephalum for many years now as both an artistic medium, and also as an engaging microorganism for my many outreach activities.

The slime mould Physarum polycephalum

In its natural environment the microbe inhabits shady, cool, moist areas, such as under decaying leaves and logs where it predates and feeds of the billions of bacteria that also reside here. If it feeds on bacteria, and indeed is exposed to them, then I reasoned that the slime mould must have some powerful bactericidal systems. With this in mind my undergraduate research project student Denford looked for antibiotic compounds in Physarum poykcephalum. He found at least one and its active against Methicillin Resistant Staphylococcus aureus.

A zone of inhibition produced by slime mould extracts in a confluent film of MRSA

The agar plate harbours confluent growth of MRSA with a well containing P. polycephalum extract in the middle. The clear zone is an MRSA inhibitory zone where the antibiotic produced by the slime mould shows bactericidal against the pathogen and prevents its growth.