S Y N T H E T I C B I O LO G Y
CREDIT: K. SUTLIFF/SCIENCE
Synthetic Biologists Design ‘Living Materials’ That Build Themselves
film and latched on to gold nanoparticles that the researchers had sprinkled into their beakers, creating a network that conducts electricity (see figure, below). By growing both batches of E. coli together, Lu’s team could vary the composition of the film just by adding AHL and aTc at different times. In this case, the varying composition didn’t add new function. But it sets the stage for doing so by binding other materials, for example. In a separate experiment, they used different peptide tags and chemical triggers to create bacteria that could trap tiny semiconductor particles called quantum dots, which altered the optical properties of the biofilm. Lu now hopes to take advantage of recent advances in synthetic biology, in which researchers have programmed bacteria to
Organisms are master builders. Crabs aren’t alive. That means, for example, that assemble shells, corals amass reefs, and our they can’t respond to their environment the own tissues build bone. Now, synthetic biol- way bacteria can: by organizing themselves ogists are taking control of the construction in groups or healing themselves. process. Researchers in Massachusetts The new work, from Timothy Lu, a reported this week in Nature Materials that synthetic biologist at MIT, and colleagues, they’ve reprogrammed the genetic circuitry brings these previously disparate fields of bacteria to construct electronic and opti- together. “Our idea is to put the living and cal materials, complete with living cells in nonliving worlds together to make hybrid their midst. materials that have living cells in them and The new materials can’t yet compete are functional,” Lu says. They started with with conventional electronic devices. Escherichia coli bacteria that naturally Nevertheless, outside researchers say the feat cooperate to produce sheetlike biofilms atop opens a new door to using genetically engineered Nonconductive organisms to assemble biofilm complex materials from the ground up, with minimal No aTc help. “It’s fantastic work,” says Lingchong You, Engineered bacteria a biomedical engineer Electrode at Duke University in to measure Durham, North Carolina, conductivityy who was not involved in Conductive His-tagged curli fibers the research. Traditional biofilm manufacturing is typically Gold nanoparticles energy-intensive, polluting, aTc and often hazardous for workers. “But if we can harness the power of cells [to build structures], we can make the entire process ‘green,’ ” You says. Filmmaker. When exposed to a chemical called aTc, bacteria produce fibers (pink) that cause them to attach to a surface and to one Moreover, because organ- another. Amino acids called histidines on the fibers then grab gold nanoparticles, forming an electrically conducting film. isms are adept at engineering materials at many different size different surfaces. The bacteria bind these form colonies in the form of rings, bars, and scales—the way our bodies imprint bone films together by secreting proteins called other shapes. That could lay the groundwork with structure on the nanoscale, microscale, curli fibers. Made up of repeated protein for more complex architectures that could and meter scale—the new work holds the subunits called CsgA, the fibers glue the serve as electrodes, environmental sensors, potential for adding new levels of complexity bacteria to surfaces and to one another. and artificial tissues. Ultimately, the living to engineered materials. For their experiments, Lu’s team first materials might be fashioned into devices The new work isn’t the first foray into disabled the genetic pathway that allows that repair themselves when damaged. marrying engineered organisms with bacterial cells to produce CsgA. They The technique might also be used to materials. In 1999, for example, Angela replaced it with an engineered genetic sponge up environmental toxins such as Belcher, a chemist now at the Massachusetts circuit that produces CsgA only when cadmium and recycle the material into Institute of Technology (MIT) in Cambridge, the researchers add a chemical trigger, complex optical and organic devices. It may and her colleagues engineered viruses to a molecule called AHL. The team then even prove useful in prospecting: Designer assemble semiconductor nanoparticles on engineered a separate batch of E. coli to bacteria, for example, might harvest gold their surfaces. Belcher’s group has since produce altered CsgA tagged with short from their environment and concentrate it in gone on to program viruses to construct protein strands, or peptides, containing mats that could be scooped up. Such tests everything from electrodes for lithium- multiple histidine amino acids, which bind remain a ways off, however. Regulators ion batteries and photovoltaics to catalysts metal particles. These bacteria expressed the would need to be convinced that engineered that split water to generate hydrogen fuel. histidine-tagged CsgAs only in response to bacteria don’t pose risks when released into But because viruses don’t harbor their own another chemical trigger, called aTc. When the environment. cellular machinery, the materials they make aTc was present, the bacteria settled into a –ROBERT F. SERVICE www.sciencemag.org
SCIENCE
VOL 343
Published by AAAS
28 MARCH 2014
1421
Downloaded from www.sciencemag.org on March 28, 2014
NEWS&ANALYSIS
CREDIT: K. SUTLIFF/SCIENCE
Synthetic Biologists Design ‘Living Materials’ That Build Themselves
film and latched on to gold nanoparticles that the researchers had sprinkled into their beakers, creating a network that conducts electricity (see figure, below). By growing both batches of E. coli together, Lu’s team could vary the composition of the film just by adding AHL and aTc at different times. In this case, the varying composition didn’t add new function. But it sets the stage for doing so by binding other materials, for example. In a separate experiment, they used different peptide tags and chemical triggers to create bacteria that could trap tiny semiconductor particles called quantum dots, which altered the optical properties of the biofilm. Lu now hopes to take advantage of recent advances in synthetic biology, in which researchers have programmed bacteria to
Organisms are master builders. Crabs aren’t alive. That means, for example, that assemble shells, corals amass reefs, and our they can’t respond to their environment the own tissues build bone. Now, synthetic biol- way bacteria can: by organizing themselves ogists are taking control of the construction in groups or healing themselves. process. Researchers in Massachusetts The new work, from Timothy Lu, a reported this week in Nature Materials that synthetic biologist at MIT, and colleagues, they’ve reprogrammed the genetic circuitry brings these previously disparate fields of bacteria to construct electronic and opti- together. “Our idea is to put the living and cal materials, complete with living cells in nonliving worlds together to make hybrid their midst. materials that have living cells in them and The new materials can’t yet compete are functional,” Lu says. They started with with conventional electronic devices. Escherichia coli bacteria that naturally Nevertheless, outside researchers say the feat cooperate to produce sheetlike biofilms atop opens a new door to using genetically engineered Nonconductive organisms to assemble biofilm complex materials from the ground up, with minimal No aTc help. “It’s fantastic work,” says Lingchong You, Engineered bacteria a biomedical engineer Electrode at Duke University in to measure Durham, North Carolina, conductivityy who was not involved in Conductive His-tagged curli fibers the research. Traditional biofilm manufacturing is typically Gold nanoparticles energy-intensive, polluting, aTc and often hazardous for workers. “But if we can harness the power of cells [to build structures], we can make the entire process ‘green,’ ” You says. Filmmaker. When exposed to a chemical called aTc, bacteria produce fibers (pink) that cause them to attach to a surface and to one Moreover, because organ- another. Amino acids called histidines on the fibers then grab gold nanoparticles, forming an electrically conducting film. isms are adept at engineering materials at many different size different surfaces. The bacteria bind these form colonies in the form of rings, bars, and scales—the way our bodies imprint bone films together by secreting proteins called other shapes. That could lay the groundwork with structure on the nanoscale, microscale, curli fibers. Made up of repeated protein for more complex architectures that could and meter scale—the new work holds the subunits called CsgA, the fibers glue the serve as electrodes, environmental sensors, potential for adding new levels of complexity bacteria to surfaces and to one another. and artificial tissues. Ultimately, the living to engineered materials. For their experiments, Lu’s team first materials might be fashioned into devices The new work isn’t the first foray into disabled the genetic pathway that allows that repair themselves when damaged. marrying engineered organisms with bacterial cells to produce CsgA. They The technique might also be used to materials. In 1999, for example, Angela replaced it with an engineered genetic sponge up environmental toxins such as Belcher, a chemist now at the Massachusetts circuit that produces CsgA only when cadmium and recycle the material into Institute of Technology (MIT) in Cambridge, the researchers add a chemical trigger, complex optical and organic devices. It may and her colleagues engineered viruses to a molecule called AHL. The team then even prove useful in prospecting: Designer assemble semiconductor nanoparticles on engineered a separate batch of E. coli to bacteria, for example, might harvest gold their surfaces. Belcher’s group has since produce altered CsgA tagged with short from their environment and concentrate it in gone on to program viruses to construct protein strands, or peptides, containing mats that could be scooped up. Such tests everything from electrodes for lithium- multiple histidine amino acids, which bind remain a ways off, however. Regulators ion batteries and photovoltaics to catalysts metal particles. These bacteria expressed the would need to be convinced that engineered that split water to generate hydrogen fuel. histidine-tagged CsgAs only in response to bacteria don’t pose risks when released into But because viruses don’t harbor their own another chemical trigger, called aTc. When the environment. cellular machinery, the materials they make aTc was present, the bacteria settled into a –ROBERT F. SERVICE www.sciencemag.org
SCIENCE
VOL 343
Published by AAAS
28 MARCH 2014
1421
Downloaded from www.sciencemag.org on March 28, 2014
NEWS&ANALYSIS
