Another type of behavior demonstrated by biofilms growing under laboratory conditions is spiral migration, demonstrated in the time-lapse video below of Bacillus mycoides. These bacterial cells grow in long chains or filaments that curl either clockwise or counterclockwise. The specific advantages of this spiraling movement are still under investigation, according to Chimileski, but they must be considerable because B. mycoides excels at taking over available environments. “Bacillus mycoides is one of the easiest bacterial species to cultivate from the soil,” he explained. When scientists isolate microbes from soil and grow them on agar dishes, particularly at room temperature, “the mycoides will often spread across the entire plate and overtake all of the other organisms. For this reason, it is considered if anything a kind of ‘nuisance species’ for many microbiologists.”

What’s curious is that the direction of the spiraling migration — clockwise or counterclockwise — seems to be a hereditary trait: Different strains of bacteria, even within the same species, spiral in different directions. It is yet another example of how bacteria, obeying instructions in their individual DNA, can manifest problem-solving behaviors that are surprisingly complex and adaptive at the collective level of biofilms.

These geometric and presumably functional patterns that biofilms produce in culture are intriguingly beautiful. Yet Chimileski notes that there is much left to discover when it comes to translating behaviors seen in the lab to natural microbial communities.

Chimileski points out that “most natural biofilms are multi-species ecosystems and cells inside natural biofilms usually grow more slowly.” He continued, “I like to think of the way we grow bacteria in a petri plate, where a single species is by itself and has everything it needs to grow at optimal temperatures, as ‘turning up the volume’ on the biology of the organism.” Under laboratory conditions, researchers can study which genes are involved in complex multicellular behaviors and they can measure the benefits to the fitness of the bacterial species. But in natural environments, biofilms don’t usually get to form exactly the same patterns as in the lab because of limited nutrients or competition with other species. “So the same biology might be occurring on a particle of soil in your backyard at smaller size scales and over longer time periods,” he said, even if it is less easy to visualize.