January 18, 2000
Volume 52, No. 17
Bacteria aids in research
Following a rash of highly publicized food poisoning incidents in recent years, the E. coli bacteria strain has jumped off the headlines of American papers and firmly implanted itself into the national consciousness. What many people do not know is that microbiologists have long used the bacteria for research.
Vincent Conticello, assistant professor of chemistry, uses E. coli to fabricate human tissues. Specifically, Conticello manufactures a polymer much like the body's elastin, which is the scaffolding for the body's organs and cells, with a unique structure that promotes cell interaction.
For the synthesis of his biological polymer, Conticello drew on the knowledge of the 70-year-old polymer science field. "When synthetic polymers first came to the fore, they were trying to emulate the properties of biopolymers," he said. "But of course there was no way for directly manipulating the manufacture of biopolymers back in the 1920s." Unable to manufacture biological polymers, scientists had to remain satisfied with stealing only design. This approach was successful, and the plastics industry took off.
But in the '70s, genetic engineering allowed scientists to design polymers of natural, biological materials-the original polymer inspiration. Finally scientists could get down to the serious business of plagiarizing nature.
The DNA sequence of elastin had long been known, and Conticello produced a shortened sequence of elastin using plasmid technology. Plasmids are small, circular units of DNA that live within bacteria and use them to reproduce. Plasmids are not a part of the bacteria's DNA, but in many ways plasmid genes can interact with the host bacteria in complex pathways. Scientists take advantage of this by using plasmids to reproduce interesting DNA sequences and the products of these sequences.
First, Conticello made a cut in a plasmid, opening the circle and forming a string with two ends. Next, he mixed the gene sequence (elastin) to be reproduced with the open plasmid. The two ends of the gene bound to the two ends of the plasmid, reforming the original circle, only now with an elastin gene incorporated into the sequence. Conticello then mixed the engineered plasmid with a strain of E. coli bacteria, and each time the plasmid replicated, it also replicated the elastin gene. Essentially, he turned the deadly E. coli into an elastin factory.
Conticello's elastin is not exactly the same as human elastin; his is a closely related but simpler analog of the natural substance. Also, Conticello's engineered version has important biomedical applications. He's made novel gels out of his elastin that react in a manner much like natural tissues and could be used to perform functions such as drug delivery.
Further, if this synthetic elastin were spun into a fabriclike material, one would have a primitive tissue. Associate Professor of Surgery Elliot Chaikof is collaborating with Conticello and hoping to make biovascular materials-blood vessels and heart tissues. He also cited the importance of the history of polymer research to understand current research. "The driving force intellectually [for biovascular materials] has been the women's wear industry. You need a synthetic tube to carry blood; well, that's polyester," Chaikof said.
But the problem with nonbiological polymers is that they eventually fail. Scars form and blood clots occur at material interfaces. So biological materials, like elastin, remain better candidates for use. "We might as well copy nature," Chaikof said. "It probably knows something, even though we don't know."