Researchers examined about 35,000 chemical reactions to determine the social roles of bacteria. Their findings are published in the Sept. 7 issue of Science magazine.
New research from the Massachusetts Institute of Technology (MIT) reveals that some unlikely subjects—bacteria—can have social structures similar to plants and animals. The research shows that a few individuals in groups of closely related bacteria have the ability to produce chemical compounds that kill or slow the growth of other populations of bacteria in the environment, but not harm their own.
Published in the Sept. 7 issue of the journal Science, the finding suggests that bacteria in the environment can play different social roles and that competition occurs not only among individual bacteria, but also among coexisting ecological populations.
The National Science Foundation (NSF), an independent federal agency that supports fundamental research and education across all fields of science and engineering, funded the research.
“Bacteria typically have been considered purely selfish organisms and bacterial populations as groups of clones,” said Otto Cordero, a theoretical biologist and lead researcher on the paper, in a prepared statement. “This result contrasts with what we know about animal and plant populations, in which individuals can divide labors, perform different complementary roles and act synergistically.”
Cordero and colleagues from MIT, along with researchers from the French Research Institute for Exploitation of the Sea and Woods Hole Oceanographic Institution in Massachusetts, studied whether population-level organization exists for bacteria in the wild.
They reasoned social structure can reduce conflict within populations of plants and animals and determine aggression toward competing biological populations. The NSF says researchers found evidence by looking at direct, aggressive competition between ecological populations of bacteria. They reconstructed a large network of bacterial fights—or antibiotic-mediated interactions—between bacteria from the ocean.
The scientists analyzed interactions called interference competitions, wherein bacteria produce antibiotics as a means of chemical warfare, to gain a competitive edge by directly hindering the survival of potential competitors.
This typically occurs when bacteria compete for the same portion of habitat, according to the NSF.
The researchers assembled an all-against-all battleground for 185 closely related, but distinct, members of an ocean-based family of bacteria called Vibrionaceae. They measured bacterial compounds produced by Vibrio isolates that directly antagonized other Vibrio isolates.
The NSF says the framework provided Cordero and colleagues an opportunity to examine about 35,000 possible antibiotic-mediated interactions.
The researchers found that ecologically delineated bacterial populations act as socially cohesive units. “In these populations, a few individuals produced antibiotics to which closely related individuals in the population were resistant, whereas individuals in other populations were sensitive,” said Cordero.
Thus, aggressive chemical reactions occur between, rather than within natural populations.
“It appears to be a group effort where individuals assume the role of antibiotic producers and hence defenders,” said Polz. “Of course, competing groups could also produce antibiotics. It’s a potential arms race out there.”
“Those individuals that don’t produce antibiotics can benefit from association with the producers, because they are resistant,” added Cordero. “In other words, antibiotics have a social effect, because they can benefit the population as a whole.”
