Bacteria and other microbes love living in slimy communities that cling to riverbed rocks and swimming pool walls, contaminate factory equipment and medical implants, and sometimes coat the teeth as plaque. When such microbe gatherings stick to a hard surface, they’re called biofilms. They're also notoriously difficult to clean up, as living in a film helps bacteria weather food shortages and antibiotics better than they would alone. So why would anybody want to try to grow a biofilm?
Though many biofilms harm us now, scientists hope that in the future, they can grow genetically engineered bacteria in large, hardy biofilm communities that produce drugs or alternative fuels at an industrial scale. One research group recently reported that they've grown a biofilm with two different bacteria. Scientists can control the percentages of each type in the film.
"Suppose you want 70/30, or vice versa, or 20/80. You can easily get it," said Arul Jayaraman, a chemical engineer at Texas A&M University who worked on growing the biofilm.
Biofilms can also clear out the bacteria populations when they want, which is no easy feat.
"They can also selectively get rid of it, which I think is quite nice," said James Collins, a bioengineer at Boston University who was not involved in the research. "I overall was very impressed with the advances described," he told InnovationNewsDaily.
Jayaraman and his colleagues published their findings Jan. 3 in the journal Nature.
Having careful control of several bacteria species in a biofilm is important for running the chemical reactions future factories want, Jayaraman and Collins said. A bioreactor could have one bacteria type that produces a drug, plus a high proportion of another bacteria type to clear away a toxic byproduct of the drug-producing bacterium. Or several bacteria types might need to work together to create a complex chemical.
"If you think of a cell as a reactor and each cell does a particular reaction, you could have a complex set of reactions being done in a biofilm," Jayaraman explained.
Jayaraman’s biofilm population proportion control depended on chemical messages that the bacteria produced. His colleague Thomas Wood genetically engineered the two bacteria types in the biofilm, so that they would send and receive messages that Wood created from chemicals that E. coli naturally use to communicate with other cells in biofilms. Signals from one bacteria could tell the second bacteria population to disperse, and a chemical switch in the remaining bacteria made them break up their own biofilm.
"We show that we can form a community at will and we can tell it go away," Jayaraman said. "This gives us a tool for controlling the composition of the biofilm."
For now, the biofilms of the world are still mostly unwanted. They contaminate food processing plants and contribute to tooth decay. Some individual labs now use biofilms in a bioreactor to run chemical reactions, Jayaraman said, but factories of bacteria that produce medicines and eco-friendly fuels may still be decades away. Meanwhile, his team’s feats of bacterial engineering and population control are a step toward harnessing the slime for good.
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