Question

1 The main difference between capnophiles and anaerobic bacteria is

A The high amount of carbon dioxide that obligate anaerobes require.

B The low amount of oxygen that capnophiles require.

2.

A student rinsed the slide with acid alcohol for 40 seconds while doing Acid fast stain. What would be the possible result of the experiment?

A Acid fast cells would look red at the end

B Acid fast cells would look green at the end

C Acid fast cells would look clear at the end

D Acid fast cells would look blue at the end

3 This bacteria grows on TSI slant producing dark red slant and black precipitate in the butt; it also produces dark centered red colonies on XLD.

A Yersinia

B Shigella

C Salmonella

D Pseudomonas

Answer 1

1B. Low amount of oxygen that capnophiles require.

Capnophiles require low amount of oxygen (around 15%) where as anaerobic bacteria cannot survive in presence of oxygen.

2 A. Acid fast cells will look red. During the acid fast staining, the cells are washed with acid alcohol mixture for atleast 2-3 min to wash off the excess stain from the non acid fast cells. This prepares the non acid fast cells to take up the counter stain. Therefore, if the step is not performed accurately for the given time, all the cells will appear red (color of primary dye: carbol fuschin, red).

3  Salmonella. It produces red colonies with dark centres on XLD plate