Why most of enterobacteria in intestine r gram negative?

Answer:
why is the sky blue? (actually I know that one).
They just are, lol!
My dear, they are all gram negative! "Members of the Enterobacteriaceae are rod-shaped, and are typically 1-5 渭m in length. Like other Proteobacteria they have Gram-negative stains, and they are facultative anaerobes, fermenting sugars to produce lactic acid and various other end products."
Many members of this family are a normal part of the gut flora found in the intestines of humans and other animals, while others are found in water or soil, or are parasites on a variety of different animals and plants. Escherichia coli, better known as E. coli, is one of the most important model organisms and its genetics and biochemistry have been closely studied (wiki).
Hence, they just ARE gram Neg. be their habitat the soil or water or a gut.

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gram negative bacterias grow in an acidic medium. in intestine matrix is acidic.so,be it.

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BECAUSE THEY LIVE IN A NEGATIVE PLACE.

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