Question

Can someone compare and contrast gram positive and gram negative organisms?

Answer 1

Whether bacteria is called "gram positive" or "gram negative" all depends on what color it turns, when it's given a "gram stain."

A gram stain is a chemical that can turn bacteria PURPLE, or PINK.

GRAM POSITIVE bacteria will turn PURPLE.

GRAM NEGATIVE bacteria will turn PINK.

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Take a look at this picture:
http://tommytoy.typepad.com/.a/6a0133f3a4072c970b0162fc6173d0970d-550wi

It shows us the difference between gram negative, and gram positive bacteria.

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Take a look at the RIGHT side.
The GRAM POSITIVE bacteria.

Do you see how the gram POSITIVE bacteria has a peptidoglycan cell wall,
on the OUTSIDE?

That's why gram POSITIVE bacteria turn PURPLE,
when they're given a gram stain.

It's because the gram stain reacts with the peptidoglycan cell wall,
which makes it turn purple.

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Now, take a look at the LEFT side.
The GRAM NEGATIVE bacteria.

Do you see how the peptidoglycan cell wall is on the INSIDE?
It's covered by an OUTER MEMBRANE.

This is why the gram stain makes this bacteria turn PINK.
It's because the gram stain cannot reach the cell wall, on the inside.
So, it can't turn the bacteria purple.

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So, once again, we have two facts:

1. Gram POSITIVE bacteria have a peptidoglycan cell wall on the OUTSIDE.

2. Gram NEGATIVE bacteria have a peptidoglycan cell wall on the INSIDE,
which is covered by an OUTER MEMBRANE.

Answer 2

Gram was a scientist who invented a technique called Gram staining by which bacteria can be colorized and divided into two groups.