Scientists have long known that bacteria come in many shapes and sizes, but understanding what those differences mean has remained a major challenge, especially for species that can’t be grown in the lab. Now, a new study led by Nina Wale, an assistant professor in MSU’s Departments of Microbiology, Genetics, and Immunology and Integrative Biology introduces a groundbreaking method that could change how researchers study bacterial diversity.

The research, published in mSphere, focuses on a tiny, unculturable pathogen called Pasteuria ramosa, which infects water-dwelling crustaceans known as Daphnia. These bacteria are pleiomorphic, meaning they can take on multiple shapes during their life cycle. Until now, scientists had to rely on fluorescent labels — custom-made tags that require detailed knowledge of a bacterium’s biology — to sort and study these different forms. But for most bacteria, especially those that live in soil, water or inside animals, that kind of information simply doesn’t exist.

Wale’s team found a way around this problem. Using imaging flow cytometry, they developed a label-free technique that identifies bacteria based on how they scatter light and naturally fluoresce. These “light signatures” allow researchers to sort different bacterial shapes without needing to tag them first.