Question

1. After Examining a Gram stained slide of Micrococcus luteus under the microscope, you conclude that it__________.

1. Exists in tetrads or clusters
2. Stained purple throughout the staining procedure.

1. Only 1
2. Only 2
3. Both 1 &2
4. Neither 1 or 2

2. A typical carbohydrate fermentation medium contains a red colored Ph indicator called phenol in a nutrient broth and an inverted Durham tube to capture carbon dioxide. This culture medium is designed to determine whether a certain bacteria can ferment a certain sugar. Which of the following indicates a positive reaction for fermentation of a carbohydrate fermentation medium?

1. A red color
2. A gas bubble in the inverted Durham line

1. Only 1
2. Only 2
3. Both 1 and 2
4. Neither 1 or 2

1. A study was done to determine how soap affects microbial growth on the hand. So a researcher pressed the fingers of her hand on the surface of nutrient agar plate D for 1minute, then she washed them with antiseptic soap, and pressed the same fingers again on the surface of nutrient agar plate C for 1 minute. After the plates were incubated for 24 hrs., they were examined for microbial growth. She found 39 colonies on plate D. Calculate the per cent reduction in microbial growth.

1. 69%
2. 13%
3. 33%
4. 67%

Answer 1

1.

a. only 1

explaination: Micrococcus luteus are catalase - positive , oxidase- positive, strictly aerobic gram -positive cocci that grow in clusters. they forms bright yellow colonies om nutrient agar.

2.

b. only 2 ( a gas bubble in inverted durham line)

exlaination: in positive reaction ,after incubation the liquid in the tube turns yellow . It indicate that there is drop in the ph because of the production of the acid by the fermentaion of the carbohyldrate (sugar) present in the media.

A bubble (small or big depend upon the amount of gas production) will be seen in the inverted Durham tube.

3.

d.67%