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A new study in the journal Scientific Reports found that single cell bacteria change as they form microcolonies, forgoing “a single cell lifestyle for a communal lifestyle.”

The cells in the study had “identical features,” yet displayed “heterogeneous behavior.” Bacteria near the microcolonies’ surface exhibited increased movement thanks to microscopic appendages called pili that elongated and retracted. In contrast, bacteria in the core of the microcolonies were more static, bonded to each other by their pili.

The movement of cells with retractable pili allowed small bacterial microcolonies to combine into larger microcolonies made up of thousands of cells in just a few hours. Microcolonies are the first stage of the development of biofilms, a bacterial community that sticks to a surface. “The mechanisms at play in this development are the subject of intense scientific inquiry due to the health related importance and ubiquity of biofilms,” the researchers wrote.

A close-up of bacteria microcolonies

The research was conducted by Ph.D. candidate Kelly B. Eckenrode (Macaulay Honors College, The Graduate Center, CUNY, Brooklyn College), Professor Nicolas Biais (Brooklyn College, The Graduate Center, CUNY), Khaled Alzurqaand Hadi Nasrollahi (Brooklyn College), along with colleagues at the Max-Planck-Institute for the Physics of Complex Systems in Dresden, Germany.

The researchers found that the motility of the surface cells also led to differential gene expression — the activation of different genes — in those active cells compared to the stable cells in the microcolony center.

The study was done using the bacteria that cause gonorrhea, which the researchers said “not only enables us to understand better the physiology of an important human disease” but “could also give a new insight into the earliest steps of genetic differentiation within a group of identical bacterial cells and ultimately the evolution of multicellularity.”