Surprisingly, the researchers found that the individual bacteria that start the formation of micro-colonies have no special inherent qualities.
As bacteria move across a surface, they leave trails composed of a specific type of polysaccharide, or long sugar molecules.
"Some of the bacteria remained fixed in position," Parsek said, "but some moved around on the surface, apparently randomly but leaving a trail that influenced the surface behavior of other bacteria that encountered it."
Bacteria arriving later also lay trails, but tend to be guided by the trails from the pioneers. This network of trails creates a process of positive feedback and enables bacteria to organize into micro-colonies that mature into biofilms. By being at the right place at the right time, and by using communally produced polysaccharides, a small number of lucky cells -- often ones that come later -- become the first to form micro-colonies, which give cells many survival advantages over other bacteria.
Interestingly, these biofilms develop in accordance with Zipf's Law, which is one special form of the rich-get-richer phenomena. A well-known example of this is the distribution of wealth in the United States. Recent statistics indicate that the wealthiest 20 percent of the population have more than 80 percent of the total wealth. Most of the wealth in this elite group is in turn owned by a small elite fraction within the elite, and so on.
"It turns out bacteria do the same thing," Wong said. "By effectively taking a census of bacteria using our recently developed methods, we find that the way they organize into micro-colonies is not random, as was previously thought."
Extending the economic analogy, Wong said the research may provide insight into how to fight antibiotic-resistant bacteria. "Typically, when we want to get rid of bacteria, we just kill them with antibiotics," he said. "As a result, they develop
|Contact: Megan Fellman|