Science Homework Help

•Please choose one answer each and explain why if you can. 

Question 9

Complete the

statement: Vibrio cholerae:

a) causes a non-invasive infection of the small intestine and excretes an enterotoxin that persistently increases cAMP levels resulting in hypersecretion of Na, Cl, K, bicarbonate and water out of the gut, via pili.

b) are true marine bacteria not found in fresh water as they are unable to survive without a source of saline in the environment thus they grow extremely well on TCBS agar and turn yellow due to being able to metabolize sucrose (fruit sugar).

c) has three biovars which are Ogawa, Inaba and El Tor (haemorrhagic) and requires two prophages, an old one that encodes VHML and a new one that encodes Tox R, to induce pathogenicity.

d) are highly motile single polar flagellated, non-spore forming, catalase negative, oxidative, facultative anaerobic Gram-negative rods. They are found inside fish and oysters and cause haemorrhagic septicaemia leading to death in 50% of patients.

e) causes a non-invasive infection of the small intestine that excretes an enterotoxin that persistently increases cAMP levels resulting in hypersecretion of Na, Cl, K, bicarbonate and water into the gut, resulting in rice water diarrhoea.

Question 10

Which of these statements about the enterotoxin in cholera is false?

a) It is encoded by a prophage.

b) It has a molecular mass of 84 kiloDaltons.

c) It has an alpha subunit ADP-ribosylating toxin.

d) It has a beta subunit that binds GM1-gangliosides on enterocytes.

e) The alpha subunit ATP-ribosylates Gs-alpha which regulates activation of adenylate cyclase increasing cAMP levels.