105 Students and 2,500 Isolates: McGill’s Systematic Approach to Crowdsourcing

Samantha Gruenheid’s class of 105 students at McGill University in Montreal, Canada, has no reason to despair. The class is split into lab cubicles of about 12 students each led by a teaching assistant. This fall semester, they collected soil samples from urban and suburban Montreal and cultured a whopping 2,500 bacterial isolates! The students work in pairs to prioritize two isolates for characterization. Recently, they obtained DNA sequences from the 16S ribosomal RNA genes of these isolates and identified various genera of potentially novel antibiotic-producing bacteria, including ones they had never heard of before. Among them were Brevibacillus, Chryseobacterium, and Dyella, a genus of bacteria that was recently discovered in Tokyo, Japan. Their isolates, many of which were isolated using Potato Dextrose Agar medium, were evenly split between Gram-positives and Gram-negatives. Gram-positive bacilli and actinomycete species typically predominate in traditional bacterial isolations, which skews the biodiversity students are able to observe. Their strategy sheds light into the culture conditions and techniques we can use to recover more diverse bacteria in the soil. Dr. Gruenheid joined Small World Initiative this past summer and is a professor of microbiology who studies host-pathogen interactions. “We’re having so much fun, I love the course!” she said, speaking for herself as well as her students.