The research team, led by co-first authors, research fellows David Savage and Bruno Afonso, attached a fluorescent tag to proteins involved in building the carboxysome, then grew the tagged bacteria under a microscope.
The resulting images revealed that, instead of being randomly numbered and haphazardly placed, cyanobacteria build carboxysomes in numbers that scale with their size, and they space the factories evenly along their length. (see image, end of release)
The finding adds evidence for new ways to think about bacteria. "We had this idea of bacteria as a bag of enzymes, but that has been completely shattered," said Afonso. A single protein, called parA, acts as a kind of inner-bacterium stage manager, arranging the carboxysomes in a neat, single-file row, the researchers found. When they disabled the bacteria's ability to make the protein, the carboxysomes were distributed far more randomly.
The cyanobacteria lacking parA were also less "fit" for survival, said Savage. While wild-type bacteria cells have a consistent number of carboyxsomes, which in turn optimizes carbon processing and fitness, the knockout bacterium created daughter cells whose numbers of carboxysomes ranged from none to an excess. The daughter cells with few or no carboxysomes divide more slowly and also process fifty percent less carbon than daughter cells at the other end of the spectrum. (see video 1)
By tagging parA in wild-type bacteria, they discovered interesting dynamics in the protein. Thousands of parA proteins repeatedly cluster together and shoot quickly from one end of the bacterium to the other. (see video 2)
"It's amazing that you can generate this regularity and
|Contact: David Cameron|
Harvard Medical School