Though identifying bacteria by appearance can be difficult (and beyond the scope of that particular class), the University of Surrey's Dr. Simon Park, who teaches course BMS1035, Practical and Biomedical Bacteriology, tells Gizmag that most of the bacteria seen, which have been grown in Plate Count Agar (PCA) for three days, are harmless and typically found on human skin, such as those in the genus Micrococcus.
The exercise does occasionally show the presence of disease-causing bacterial pathogens such as Staphylococcus aureus, associated with a number of infectious diseases of varying severity. Dr. Park tells Gizmag that this isn't surprising considering that 20 percent of people are persistent carriers, and 60 percent intermittent carriers, of this species of bacteria. "The ecological niche on the body for Staphylococcus aureus is the nostrils," Dr. Park said. "So a furtive pick of the nose, and quick text after, and you end up with this pathogen on your smartphone."
Perhaps the most interesting aspect of the experiment is that the resulting bacterial culture tells a unique story of the recent history of each device and its owner. Dr. Park's favorite image is one which shows a dense, smartphone-shaped colony of Bacillus mycoides (in fact, you can make out the outline of the smartphone in a number of the images). "This pattern of growth is unique to this bacterium and because soil is its natural habitat, we know that this phone or its user had recently been in contact with soil," Dr. Park told Gizmag.
Asked how his students initially reacted to the cultures, Dr. Park told Gizmag that they were surprised at first, but fine once informed the bacteria are mostly harmless. "It’s a really good example of just how ubiquitous bacteria are in our environment and how easily they can be transferred," Dr. Park summarized.