Lab 4

Question 1

Define colonial morphology

Answer 1

The outwardly visible structure, color, and odor of colonies of a pure culture of bacteria, used to characterize that culture

Question 2

Define streak plate isolation

Answer 2

A technique involving the use of sterile nutrient agar Petri dishes and an inoculation loop to physically spread large numbers of bacterial cells over the surface of the agar until individual cells end up well separated from each other; individual colonies may grow from separated cells.

Question 3

Define pour plate isolation

Answer 3

The use of dilution of liquid bacterial samples in sterile isotonic diluents that leads to dramatically reduced numbers of cells per unit of volume in the tubes; requires multiple dilutions. The bacteria are then added to molten agar

Question 4

Define spread plate isolation

Answer 4

The use of dilution of liquid bacterial samples in sterile isotonic diluents that leads to dramatically reduced numbers of cells per unit of volume in the tubes; requires multiple dilutions. The bacteria are then spread over an agar Petri dish.

Question 5

Who created serial dilutions in broth?

Answer 5

Pasteur

Question 6

Who created diluted cultures on agar (streak plate isolation)?

Answer 6

Koch

Question 7

Define streak plate isolation

Answer 7

Carefully dilution cultures on agar

Question 8

What was accomplished during lab 4?

Answer 8

We streaked 4 Petri dishes; 3 of the 4 dishes had different bacteria (Bacillus subtilis (Bs), Staphylococcus coli (Sepi), and Escherichia coli (Ec)) and one dish had a mixed culture of all 3.
We used 3 types of streaking techniques: continuous, quadrant, and t-streak

Question 9

What were the 3 types of streaking techniques used?

Answer 9

Continuous, quadrant, and t-streak

Question 10

Describe how to do continuous streaking

Answer 10

Deposit the loop into a dot at the top of the plate, then drag some of that bacteria across the entire Petri dish, making squiggly lines with the loop

Question 11

Describe how to do quadrant streaking

Answer 11

1) Divide the plate into 4 even sections and label them
2) Apply a loop of bacteria and spread across the entire first quadrant
3) Sterilize loop and drag the loop through quadrant 1 into quadrant 2, making a zig-zag pattern
4) Sterilize loop and drag the loop through quadrant 2 from bottom to the top, then drag the loop through quadrant 3 making zig-zag pattern
5) Sterilize loop and drag the loop through quadrant 3 from bottom to the top, then drag the loop through quadrant 4 making zig-zag pattern

Question 12

Describe how to do a T-streak

Answer 12

1) Divide the plate into 2 large sections and one small section at the top; label the small section as 1 and the others as 2 and 3
2) Apply a loop of bacteria and spread across the entire first quadrant
3) Sterilize loop and drag the loop through half of quadrant 1 into quadrant 2, making a zig-zag pattern
4) Sterilize loop and drag the loop through quadrant 2 from bottom to the top, then drag the loop through quadrant 3 making zig-zag pattern