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Old 03-23-2015
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Default Gram stain limitations

Hello everyone,

I am wondering if anyone here can explain to me why an intracellular parasite like legionella, rickettsia, and chlamydia does not show on a gram stain?

Also, correct me if I am wrong, it is the peptidoglycan of the cell well that gets stained?

Finally, for mycobacteria, the reason it is not stained is because of the high lipid content? but gram negative bacteria also have high lipid content, so why is it that each one behave differently?

thanks in advance.
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Old 03-23-2015
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Quote:
Originally Posted by yagoy View Post
Hello everyone,

I am wondering if anyone here can explain to me why an intracellular parasite like legionella, rickettsia, and chlamydia does not show on a gram stain?
All either have thin walls that can't be stained or have modified walls such as chlamydia which doesn't have muramic acid (which interferes with the staining).

Quote:
Also, correct me if I am wrong, it is the peptidoglycan of the cell well that gets stained?
Yes, it is the peptidoglycan layer.

Quote:
Finally, for mycobacteria, the reason it is not stained is because of the high lipid content? but gram negative bacteria also have high lipid content, so why is it that each one behave differently?
It has a reaaaally thick and strong lipid wall that even allows it to resist phagocytosis! It's not your ordinary lipid wall
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Old 03-24-2015
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The parasites are INTRAcellular. They can't be stained when infecting the inside of the cell
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