BLOODY COUNTING: A stack of Silvio Brugger’s blood agar plates for growing bacterial colonies.PHOTO BY PASCAL M. FREY/COURTESY OF SILVIO BRUGGERWhile studying bacterial resistance to penicillin in medical school, Silvio Brugger was horrified to discover that he and a colleague would have to count colonies growing on 100 or so petri dishes every day. He thought, “Oh my God, I cannot do this,” says Brugger, now working at the University of Bern in Switzerland. “It was quite painful.”
Brugger is hardly alone: if you want to know how many bacteria or viruses you have, the standard method is to plate serial dilutions and count the resulting colonies or plaques. While some scientists may not mind the repetitive activity—“I don’t find it too bad,” says virologist Vincent Racaniello of Columbia University in New York—others find the work incredibly tedious. Yet tallying each speck by hand remains the technique of choice in most labs that study bacteria or yeast, says Martin Smith, sales manager at Synbiosis in Cambridge, U.K., which makes automated colony counters. In virology, plaques are the best way to confirm that viruses completed the full infectious cycle, says Racaniello, who studies polio- and rhinovirus in animal cell culture.
However, scientists faced with ...
