A single bacterial cell is invisible to the naked eye. As that single cell grows and divides into new cells, however, it forms a visible pile of bacteria. In microbiology, we call this pile of bacteria a colony. A colony’s appearance can indicate a lot about the bacterial cells within, such as how they utilize nutrients, if they carry genetic mutations, and how the bacterial cells are interacting with one another. In his “Colonies” series of images, Ian Hill highlights some of the diversity seen in colonies of Pseudomonas aeruginosa, a common bacterium that is both a useful model organism in microbiology and a potentially dangerous pathogen to humans.

Contributed by Ian Hill, a fifth year graduate student in the Biological and Biomedical Sciences program at Harvard University, and our Featured Artist for January and February, 2018. To meet Ian and see more of his art, click here.