I know that the stomach is highly acidic, but the actual intestines themselves are somewhat neutral. So does anyone know the pH of the gastrointestinal tracts? (if i'm right, the place where the stomach and the intestines connect) also if possible list some bacteria that lives in the gastrointestinal tracts

The gastrointestinal tract is generally taken to mean the tube in the body from the mouth to the anus.

 

Stomach pH is between pH 1 and pH 3.5 in the fasted state. The pH of the small intestine is between pH 5 and pH 7, increasing along the small intestine. The pH of the mid-distal duodenum, the part of the GIT immediately after the stomach, is pH 4.9 in the fasted state.

 

Passage of material from the stomach to the duodenum is controlled by the pyloric sphincter. Presumably release of stomach contents into the duodenum would initially cause a reduction in the pH, but this would quickly be corrected by increased bicorbonate secretion from the Brunner's glands.

 

Not very much lives in the stomach, though lactobacillus and candida (a yeast) are part of the normal flora. In terms of pathogens, Helicobacter pylori lives in the stomach and causes ulcers. The normal flora of the small intestine includes E.coli, lactobacillus and enterococcus, while for the large intestine (the colon) it includes E.coli, enterobacter and klebsiella.

 

For more information on normal GIT flora, see http://www.vacadsci.org/PUB/micro17.pdf

http://textbookofbacteriology.net/normalflora.html