Can you guess the medium used to create these art pieces?

Finnish artist Erno-Erik Raitanan has created a visually arresting series of art pieces using a most unusual medium. Can you guess what it is? What if I told you that the name of the series is "Bacteriograms"? Give up? Answers after the jump.

According to Raitanan, the images were created by cultivating bacteria samples on a color negative film. He describes his process, and the motivation behind it:

Can you guess the medium used to create these art pieces?As the name Bacteriograms implies, this series is closer to photograms than photographs. These images are made without a camera, by cultivating bacteria on the gelatin surface of the negatives, using a similar process as the one used in laboratories to grow bacteria on agar in petri dishes. With this work I want to raise questions about representation and reality; the nature and the place of photographic medium in contemporary society.

Can you guess the medium used to create these art pieces?I have gathered the bacteria samples from my own body. The bacteria consumed the film surface, producing photographic images that are entirely created by a chance. I have been removed from the process but, at the same time, the images are a product of my body; self-portraits.

Can you guess the medium used to create these art pieces?I see Rorschach inkblot test with black ink on a white paper as the closest reference to Bacteriograms. Only individual's perception and psyche dictates the representation of the image and therefore is supposed to reveal something from the viewer's subconscious. Bacteriograms play with the way we perceive and read into photographs by offering the viewer a photographic blot to project their representation.

Can you guess the medium used to create these art pieces?Bacteriograms are not even showing the bacteria that created them; they merely show the traces of bacterial activity. These images are just a piece of degraded and therefore deconstructed film, which reveals us the components that create the illusion we perceive as a reflection of the reality in the photographic image.

You'll find more examples of Raitanan's work on his website.
[Spotted on NOTCOT.org]