科学美国人60秒:Penicillins Reveal Additional Antibacterial Power

Tis the season for infections.  And if you wind up with a prescription for penicillin or its relatives, you’re getting a gift that’ll give those unwelcome bacteria a double whammy. Because a new study shows that the penicillins wipe out infections by delivering a lethal one–two punch. The findings are revealed in the journal Cell. [Hongbaek Cho, Tsuyoshi Uehara and Thomas G. Bernhardt, Beta-Lactam Antibiotics Induce a Lethal Malfunctioning of the Bacterial Cell Wall Synthesis Machinery]
 
Scientists have long known that penicillin and its relatives disrupt the assembly of the bacterial cell wall, a tightly woven mesh made of peptide-studded sugars called peptidoglycans. The drugs bind to enzymes that produce peptidoglycans and then link them together.  That interaction shuts down the enzymes’ cross-linking capabilities. Without the cross-links, the cell wall collapses. And the bursting bacteria die.
 
But the full effect of the antibiotic, in widespread use since World War II, was not appreciated til now.
 
In the new study researchers treated bacteria with a form of penicillin and then watched what happened to the cell wall components. As expected, the drug blocked cross-link formation. But the surprise was that the enzyme that can no longer forge links doesn’t just sit there. It continues to churn out unlinked peptidoglycans—which the bacteria don’t want piling up, so they rapidly degrade.
 
This futile cycle of synthesis and destruction depletes bacterial resources, speeding the path to . The finding could point the way toward the development of new antibiotics—ones that are similarly multitalented when it comes to wiping out what ails you.
 
—Karen Hopkin