Question

1. What is the importance of generating isolated bacterial colonies?

2. Describe how a bacterial sample would be obtained from and inoculated into each of the following types of media.

Agar slant:

Agar plate:

Broth:

4. What is a subculture?

6. How would a subculture appear if a colony containing both S. marcescens and M. luteus was subcultured to

a slant?

7. Condensation often gathers in the bottom of agar slants. Why is it important in this exercise to limit

condensation on plates but not on slants?

8. Which separation method is not appropriate for use with cultures containing a great deal of bacterial

growth? Why is this method not a good choice for these conditions?

9. Why is agar cooled to 50°C prior to being inoculated with bacteria? What would happen if the agar were

significantly warmer or cooler when inoculated?

10. How could you identify a potential contaminant on a streak plate? A pour plate? A spread plate?

11. How would any of the the isolation techniques seen in this laboratory exercise be affected by the use of

selective medium?

Answer 1

1. Its is to get one type of culture which means one no contamination of culture with other organisms. if observing through microscope one type of cell is seen , it is pure culture.

2. Agar slant: Obtain- Rotate tube around the loop, Inoculate: Same method

Agar plate: Obtain- Toching the colonies using the needle, Inoculate- By streaking on the plate

Broth: Obtain- The loop is submerged in medium, Inoculate: same method

4. Subculture is the culture is made by tranferring the organisms from a previous culture to a freshly prepared media. The subculture are made from liquid - solid media , solid to solid and liquid - liquid.

6.  S.marcescens: Red coloured growth on media

  M. luteus: Yellowish green or yellow coloured growth on media

7. From the liquid the bacteria growns onto the slant in isolated colonies. And the condensation in the plate prevent the forming of isolated colony.

8. Spread plate method, where the bacterial growth is limited which means in this method allow to grow only limited number of bacterial colonies or cell.

9. The optimum temperature were the bacteria growth occurs is 50 degree celcius. If the temperature slightly increase (warmer) or decrease (cooler) it will affect the bacterial growth (kill bacteria).

10. A streak plate : The growth other than in the streak lines are contaminants.

A pour plate : The bacterial appereance difference in the colony comparing to the rest of the colonies.

A spread plate : It is little difficult, cannot identify by the first appearence. It depends upon size, colonies characters and colour of the colony ( for example: micrococcus grows with staph).

11. The proper growth of the bacterium  is may not be allowed there.