chapter 27-3

Question 1

Normal microflora of the GI tract

Answer 1

Consists of stomach, small intestine and large intestine.
Responsible for digestion of food, absorption of nutrients and production of nutrients by indigenous microbial flora.
Contains 10^13 microbial cells (far more than rest of body combined).

Question 2

Normal microflora of the GI tract: Populations

Answer 2

Microbial populations in different areas of GI tract influenced by diet and physical conditions.
Acidity of stomach and duodenum of small intestine prevents many organisms from colonizing the GI tract.

Question 3

Stomach

Answer 3

Few bacteria: low pH, swift passage. 
Exception: helicobacter pylori
-found in >60% of adults. 
-Gram neg
-pH 6 ideal
-burrows into gastric epithelium
Causes: gastritis, ulcers and gastric cancer. 
--70% of infections are asymptomatic. 
--Discovered by Barry Marshall and Robin Warren.

Question 4

1950’s U.S. Army

Answer 4

Pathogenic cholerae administered to healthy volunteers, few contracted cholera.
Incidences of cholera very high among malnourished.

Question 5

Large Intestine

Answer 5

Long transit time (10-100 hrs). 
Low redox potential. 
1-2kg of microbes. 
>1000 bacterial and archaeal species. 
60% of fecal mass= microbial cells 
1000 anaerobes: 1 aerobe.

Question 6

Individual level variability in gut communities

Answer 6

Breast vs. formula fed. 
Diet
Genetics 
antibiotics 
obesity- alters gut microbial ecology.

Question 7

Harvest of energy and nutrients from the diet

Answer 7

Gut microbes increase efficient digestion of otherwise inaccessible nutrients and/or sources of energy from the diet.
Energetic value of food is not absolute but determined by an individuals microbiota.
~20% of host energy balance in omnivorous mammals .
~70% of host energy balance in herbivorous mammals.

Question 8

Benefits to…

Answer 8

Vitamin production
Prevent colonization
Production of… inhibitory to pathogens