Bacteria in laboratories usually thrive on buffets of nutrient-rich agar, resulting in nondescript blob-like colonies. The images here reveal what happens in nature, when microbes confront challenges such as antibiotics or limited food.
The patterns are both beautiful and functional, says Eshel Ben Jacob, a professor of physics at Tel Aviv University. Swirl-like vortex and branching shapes, for instance, result from the delicate balance between density requirements and nutritional needs. Bacteria move around in lubricating fluid that requires a collective effort to produce, so they need a high density of cells, he says. A vortex, or spiral, maximizes local concentration of bacteria but leaves space between branches so that, on average, colony density remains low. In nature, this is critical since food is precious, and the colony that grows too crowded starves.
Ben Jacob’s petri dishes are part of a joint-research project with the Center for Theoretical Biological Physics at UC San Diego attempting to unravel the adaptation secrets that have made bacteria the most successful life form on Earth.
The bacteria are smart enough that when they have hard conditions, instead of competing with one another, they act collectively, says Ben Jacob. Using a system of chemical communication known as chemotaxis, bacteria shape the structure of their colonies, sometimes sending an attractive signal, sometimes sending chemicals that tell others to ‘stay away.’
Bacteria also communicate to rally forces against antibiotics. In one of the most provocative examples of microbial social intelligence, the team has discovered that when certain opportunistic bacteria take advantage of the group effort, these cheaters are shut out of the community. The bacteria collectively alter the expression of their genes, shifting into a dialect that becomes unintelligible to the cheater.
Until very recently, much was unknown about the language of microbes. Since we’ve treated them as dumb, solitary creatures, we’ve used antibiotics in a careless way—in agriculture and medicine, says Ben Jacob. If we better appreciate their intelligence, we’ll be able to harness bacteria for our benefit.
Originally published March 25, 2010