Science Buddies: "Ask an Expert"

Hi
Testing for antibiotic resistance could be done using mass sensors that detects growth rate of bacteria colonies [1] in dishes. My question is if we are sensing mass, from where did the bacteria "obtain" this bio-mass? Shouldn't the total mass of the dish be constant even if the bacteria proliferated ? If yes then what is going on? How are we detecting mass increase?

[1] Ivanov, Dentcho. "BioMEMS Sensor Systems for Bacterial Infection Detection." BioDrugs 20.6 (2006): 351-356.

Aladdin,

Good question. It seems that petri dishes are not designed to be airtight, so the law of conservation of mass does not apply. The bacteria would extract oxygen and other matter out of the air, adding it to their body mass and increasing the weight of the dish.


For science!

- Ultra