The process begins when the baseplate recognizes and binds to a suitable receptor on an anthrax bacterium. This binding causes the baseplate to immediately change its shape to a more open, clawlike structure, which in turn signals the sheath to contract to nearly half its length.
"When it contracts the tube has no choice but to be driven into the cell, much like a syringe," Morais said. "And in addition to contracting, the tail sheath is rotating, and that rotation exerts a torque on the neck protein, which opens the neck protein up so that DNA can now flow from the head into the tail, and then through the tail into the host cell's cytoplasm."
Morais' interest in SBP8a goes beyond the mechanics of its replication. He and his colleagues would like to take advantage of the fact that unlike other anthrax bacteriophages, SBP8a bonds to anthrax spores, not just anthrax bacteria. That gives it the potential to serve as the basis of a highly efficient detection system for the deadly agent.
"We want to push to high enough resolution where we can see secondary structure and make reliable models, and really rationally engineer these type of things," Morais said. "The genome has been sequenced now, and we're figuring out which parts can be removed and replaced with green fluorescent protein the first step to endowing these bacteriophages with a reporter capacity and making them a detection tool.
"The great thing about our approach is that it is completely flexible. Every pathogenic bacterium has a phage associated with it. Thus, one could imagine tagging each pathogen-specific phage with a different colored signaling molecule such that you could make a cocktail of modified phages that glows a different color depending on which bacteria is present. Such a kit could be used to quickly identify a pathogen present in a bioterror attack."
|Contact: Kristen Hensley|
University of Texas Medical Branch at Galveston