Sean Crosson: Bacteria in LOV

© 2007 Chris Lake Photography

Earlier this year, University of Chicago assistant professor Sean Crosson donned a cowboy hat and rode a giant foam bacterium across a stage as part of a student research presentation. The audience broke into laughter.

While exploring the "hidden biology" of undescribed signaling pathways in the bacteria, Caulobacter crescentus, Crosson's group manages to share quite a few laughs, and the lab leader is often the ringleader. "People in my lab work hard and they're serious about it, but no one's too intense," says Crosson in the fading drawl of his native Texas. "I want people to have fun. We're not here to be miserable."

As a PhD student in Keith Moffat's University of Chicago lab, Crosson used X-ray crystallography to solve both the dark state ¹ and photo-excited ² structures of the light, oxygen, or voltage (LOV) domain of the plant protein phototropin, a mediator of the light orientation behavior of seed plants. Crosson capped his PhD study with a review paper ³ that outlined the current state of knowledge regarding LOV and foreshadowed his future study of the highly conserved domain's function in bacteria.

Moffat says he was impressed by Crosson's quiet confidence as the unprecedented results of his research flowed in. "I knew Sean was getting it when, at a pretty early stage in his academic career, he was quite prepared to argue with me and showed lots of signs of being right," remembers Moffat.

In 2003, Crosson made the leap from structural to cell biology as a postdoc in Lucy Shapiro's Stanford lab, where he turned to bacteria and studied the function of LOV domains present in photosensory histidine kinases found in many bacterial species. Shapiro says that, in addition to his sense of humor, Crosson's ability to "speak multiple scientific languages" is one of his defining characteristics. "He'll learn anything he needs to learn to answer important questions," she says. "That is the hallmark of an extraordinary scientist."

Recently, Crosson and several of his advisees found that these photoactivated proteins in Caulobacter enhance the cells' ability to attach to objects in their environment. ⁴ Crosson and his group suggest that Caulobacter cells in freshwater bodies may use this mechanism to cling to scarce nutrients in well-lit surface layers.

Crosson's former mentors expect a fruitful career for the young scientist, but it is doubtful that Crosson will ever forsake his sense of humor in the pursuit of science. "He's got a lot of energy and is really focused on his work," says Erin Purcell, Crosson's current PhD student, "but he's also really willing to act like a goon."