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David Plaut: Off the Cuff

An Intriguing Story of the Evolution of a Group A Streptococcus

Published May 1, 2014 2:51 AM by David Plaut

The ability to determine the entire genome of bacteria has led to the identification of how a harmless bacteria in only 4 steps became a deadly, widely appearing clone. Step 1 was that the precursor cell contained a phage that encoded an extracellular DNase. In Step 2, the cell acquired a variant, (SpeA1) streptococcal pyrogenic exotoxin A superantigen. The next Step was the evolution of the SpeA1 into the SpeA2 through a single nucleoide change. Step 4 was the acquisition in the early 1980s of a 36-kb region that encoded two toxins. The authors pointed out that “molecular evolutionary events transpiring in just one bacterial cell ultimately have produced millions of human infections worldwide."

posted by David Plaut

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