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Name: Melly
Status: student
Grade: n/a
Location: Outside U.S.
Country: Malaysia
Date: Winter 2013-14

Question: Why bacteria in yogurt is gram positive?

Hello Melly,

The bacteria in yogurt such as Lactobacillus acidophilus La-5 are able to fight against gram negative e coli bacteria (Enterohemorrhagic Escherichia coli). The gram positive yogurt bacteria may simply be strong enough to crowd out other species. I hope this helps.


Gram negative bacteria have an outer lipid membrane that can have toxic properties and is permeable to small molecules. Gram positive bacteria are composed of 90 percent peptidoglycan, which is not as permeable. Teichoic acids are embedded in the cell wall to make it negatively charged. The chemical composition and cell surface properties of the gram positive cell wall help lactobacillus to be resistant to acidic conditions.

Judy L

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