Microbial Painting

For my microbial painting, I chose to keep things simple in an attempt to reduce unexpected results and produce a visually pleasing piece. However, there was clearly some unexpected cross-contamination! For this piece, I used EMB agar (which selects for gram-negative bacteria and differentiates between lactose fermenters and non-fermenters) as my “canvas” and two strains of bacteria as my “paint.”  Citrobacter freundii,  a strongly acidic fermenter of lactose, turns dark red on this medium, and so I used it to outline and fill my heart. Then, I used  Proteus mirabilis, a less acidic lactose fermenter, as my ” pink paint” for the small dots along the edge of the plate. There was some cross-contamination along the outline of the heart, which I suspect is a result of cells dropping off of the loop when I lifted it over the plate. An unexpected result, but very pretty nonetheless!