futuredoctor10

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In the EK Biology Content book, I think there is an error in Lecture 3 Microbiology, Section 3.7 Bacterial Envelope on p. 64-67.

The book says gram-positive bacterium have a periplasmic space.
"Gram-positive bacteria... The space between the plasma membrane and the cell wall is called the periplasmic space."

I always learned gram positive bacteria have a plasma membrane and cell wall, while gram negative bacteria have a plasma membrane, cell wall, periplasmic space, and outer membrane. Thus I thought the periplasmic space + outer membrane are unique to gram-negative bacteria.

is EK wrong?
 

TheBoondocks

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In the EK Biology Content book, I think there is an error in Lecture 3 Microbiology, Section 3.7 Bacterial Envelope on p. 64-67.

The book says gram-positive bacterium have a periplasmic space.
"Gram-positive bacteria... The space between the plasma membrane and the cell wall is called the periplasmic space."

I always learned gram positive bacteria have a plasma membrane and cell wall, while gram negative bacteria have a plasma membrane, cell wall, periplasmic space, and outer membrane. Thus I thought the periplasmic space + outer membrane are unique to gram-negative bacteria.

is EK wrong?
Technically yes, but in reality no. Only gram- have an "official" periplasmic space. However, gram positive have space between the cell wall and the plasma membrane, and this is what EK is talking about. Both types still need an area to pump out H+ and the difference is that in gram+, this space is between plasma membrane and cell wall. Whereas, in gram- it's between outer membrane and plasma membrane. It's just easier to reference the area where H+ is pumped as periplasm for both.
 

futuredoctor10

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Thanks that helps. I am guessing this wouldn't come on the MCAT since different sources (texts, online resources, prep books) say different things!
 
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TheBoondocks

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Thanks that helps. I am guessing this wouldn't come on the MCAT since different sources (texts, online resources, prep books) say different things!
Ha, yea I was confused about that too but we covered it in my micro class. Finally, yea, the MCAT won't ask, but if they do, the best answer is Gram-.
 

futuredoctor10

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yea, the MCAT won't ask, but if they do, the best answer is Gram-.
OK so just checking: if they ask some sort of question, we should assume periplasmic space is for Gram negative only.
 

TheBoondocks

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