Diversification helps reduce overall risk by putting your eggs in more than one basket and is a strategy that strengthens groups of all kinds -- from forests challenged with environmental stress to stock market portfolios in uncertain times. Findings from University of Iowa researchers show that even bacteria have learned this important lesson.
When disease-causing bacteria assemble into communities known as biofilms, the individual bacteria rapidly diversify. This diversity increases the capabilities of the group and provides a form of "biological insurance," which protects the organisms from adverse conditions. The findings will appear the week of Nov. 15 in the Proceedings of the National Academy of Sciences.
In the past few years, researchers have found that bacteria living in biofilms are responsible for many chronic human infections such as cystic fibrosis lung infections, heart valve infections and wound infections in people with diabetes. In biofilms, organisms live clustered together, encased in a self-produced slime.
"Biofilm infections are a major medical problem, and one focus of our lab is to understand why the biofilm lifestyle makes bacteria so difficult to eradicate," said Pradeep Singh, M.D., assistant professor of internal medicine and microbiology in the UI Roy J. and Lucille A. Carver College of Medicine and the study's principal investigator.
Previous work has shown that living in groups gives the bacteria properties they do not have as individuals, including increased tolerance to antibiotics. The new findings suggest biofilm growth may provide another key advantage.
Using a laboratory model, the UI team found that when biofilm communities were established using a small number of identical bacteria, a remarkable degree of diversity rapidly developed in the population.
"After only a few days of biofilm growth, the bacteria diversified in their nutritional requirements, ability to swim, capacity for dissemination, production of protective substances, as well as in other traits," said Matt Thoendel, a UI medical and doctoral student who contributed to the work.
"This was very surprising," said Blaise Boles, UI graduate student and another of the study's authors. "Even more fascinating was that diversification was only generated when the bacteria assembled into communities."
This finding led the researchers to draw parallels to other biological communities in which diversity has been studied.