Normal Flora

Question 1

describe normal flora of the skin

Answer 1

dry and lower aw. acidic, sweat contains NaCl and lysozyme. limited nutrients

Question 2

conditions of skin promote what

Answer 2

growth of few gram +ive species like Staphylococcus epidermidis

Question 3

flora of proximal small intestine

Answer 3

relatively few bacteria due to low pH, bile sales damage some bacterial membranes, 02 is toxic to obligate anaerobes

Question 4

flora of small intestine further along

Answer 4

pH is neutral, biles salts reabsorbed, lots of nutrients, # of bacteria increases

Question 5

flora of large intestine

Answer 5

humans don’t have enzymes to digest complex carbs like oligosaccharides in beans, fibres like pectin in fruit. indigestive matter passes into large intestine

Question 6

majority of bacteria in large intestine are

Answer 6

gram -ive obligate anaerobes like Bacteroides

Question 7

describe Bacteroides thetaiotamicron

Answer 7

large genome encodes many enzymes that enable catabolism of wide variety of plant saccharides of human-derived carbs

Question 8

human carb are found in

Answer 8

mucus and glycosylated molecules on the surface of epithelial cells

Question 9

how are short chain fatty acids made

Answer 9

undigested carbs enter large intestine and rapidly fermented by Bacteroides. produce acidic waste like acetate and butyrate (pH drops) that are known as SCHA

Question 10

fn of SCFA

Answer 10

absorbed by epithelial cells and used as main source of nag. stimulate growth of epithelial cells and increase uptake of ions like calcium and iron

Question 11

in the normal flora E. coli catabolizes

Answer 11

gluconate component of mucus, uses the ED pathway

Question 12

normal flora synthesizes vitamins for us such as

Answer 12

vitamin K, we absorb half of daily intake from our intestine when various bacteria synthesize them

Question 13

explain fn of Bacteroides thetaiotaomicron when fucose levels low

Answer 13

species detect level of fucose in intestine. when low levels, bacteria secrets protein that is take up by intestinal cells. protein signals intestinal cells to increase fucose amounts added to glycosylated molecules.

Question 14

explain fn of Bacteroides thetaiotaomicron when fucose is bound to host cell

Answer 14

bacteria secretes an enzyme that cleaves the fucose from glycosylated host cell molecule once inside bacterial cell fucose binds to fucose operon repressor. fucose operon is expressed, fucose is catabolized