Science Buddies: "Ask an Expert"

Hello,
I am researching the impacts of artificial sweeteners (sucralose, acesulfame potassium, aspartame, saccharin) on the growth of lactobacillus acidophilus. I purchased five tubes of the freeze dried viable cultures from Carolina (http://www.carolina.com/bacteria/lactob ... cidophilus) and am planning to inoculate the bacteria for 48 hours at 37° C in the provided medium. After, I plan to expose the bacteria to a solution made of artificial sweetener and distilled water and again incubate them for 48 hours at 37 °C in the same test tubes and growing media. I hope to analyze the amount of bacterial growth when exposed to each of the artificial sweeteners compared to the untouched control. However, I am concerned as how to tell if the bacteria are alive or dead. Is there a way to determine if bacteria grown in liquid media are alive or dead? Thank you for your help.

Hello Kef2018,

That sounds like an interesting experiment! Whether or not you can tell the difference between dead and live bacteria in a culture depends on the strain, in many cases you can tell. However, certain strains will lyse (remove) the dead cells, so taking a density measurement would then reflect the total amount of living cells. I believe that with lactobacillus this is the case.
This troubleshooting guide will hopefully help.
https://www.sciencebuddies.org/science- ... oblems.pdf

Good luck,
Elizabeth

Thank you so much for your help!