Chemists have discovered the most naturally variable protein known to date in a bacterium that is a key player in the formation of dental plaque. The two UC San Diego chemists, who announced their discovery in this week’s early online edition of the journal Proceedings of the National Academy of Sciences, say they believe the extreme variability of the protein they discovered in the bacterium Treponema denticola evolved to adhere to the hundreds of different kinds of other bacteria that inhabit people’s mouths.

They call the protein they discovered “Treponema variable protein,” or TvpA for short, and estimate that it is a million to a billion times more variable than the proteins that play a primary role in vertebrate immune systems—the only other known natural system for massive protein variation.