Streak plate technique

Inoculation of an agar plate

Lesson 16

1. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

coolness прохлада

cultivation разведение, распространение

throughout через; по всему

exposure подвергание какому-л. воздействию

give rise вызывать, давать повод, давать начало

2. Master the following words.

Petri dish - чашка Петри

inoculation - прививка

streak plate - штриховая пластинка

diluting - разжижающий

contamination - загрязнение; порча

3. Put down the Russian for:

agar plate

mixed culture

agar surface

kidney material

apparent

4. Translate the following words and word combinations in writing.

bacteriological loop ______________________________________

sample ________________________________________________

sterile loop _____________________________________________

parallel streaks __________________________________________

clinical note ____________________________________________

physical damage ________________________________________

adequately padded ______________________________________

5. Put down the verbs. Translate the words.

Model: cook, to cook – готовить

Use, to _______________ - _________________________

Present, to ____________ - _________________________

Place, to _____________ - _________________________

Cool, to ______________ - ________________________

6. Translate the following questions.

1) What are Petri dishes used for?

2) How is the colony of organisms originated?

3) Organisms in one colony are identical, aren’t they?

4) Are plates used for this purpose dry?

7. Read the text. Find the answers to the questions given above.

Petri dishes containing solid medium (agar) are used to provide a large surface of media for the cultivation of micro-organisms. Inoculation of an agar plate is often carried out using the streak plate technique.This involves diluting the culture or other sample, e.g. kidney material, by smearing it across the surface of the agar. Organisms present in the sample will be separated and after suitable incubation each organism present will give rise to a colony. Although this colony contains many millions of organisms they will have all originated from one, and therefore all organisms in one colony are identical.

By using this method organisms can be cultured in the laboratory and if a mixed culture is present it will become apparent on plating out. This is essential before starting identification procedures as methods are only valid when carried out on pure cultures, i.e. cultures containing one type of organism. Care should be taken that plates used for this purpose are dry. Also avoid unnecessary exposure of the agar surface to potential contamination from the environment throughout the procedure.

8. Read the text and put the sentences in the right order.

1. Sterilize a bacteriological loop and allow cooling.

2. Pick up a small amount of sample using the sterile loop.

3. Inoculate the sample on a segment of the surface of the culture medium.

4. Sterilize the loop; allow cooling and touching edge of uninoculated area of medium to ensure coolness.

5. Spread part of the sample over about a quarter of the plate by making 3-4 parallel streaks with the loop.

6. Repeat streaking procedure as shown, sterilizing and cooling the loop between each sequence.

7. Label the underside (not lid) of the plate, writing only at the edge, and incubate or dispatch with related clinical notes and history. Ensure dispatched sampled are adequately padded to protect against physical damage.

(Answer: 1,2,3,4,5,6,7.)

9. Pair work. Discuss streak plate technique at the lesson. Put questions to your group-mate and ask him/her to answer them.

Дата добавления: 2014-12-26