Pure culture technique

Prepared bySamira fattah

Assis. Lec.College of health sciences-HMU

Lab 7

• Pure culture: is a culture that contains a single known

species or type of Microorganism.

Aim:To identify the bacterial pathogens.

• Mixed culture need to be separate.

• The most commonly used method in the laboratory for isolating microbes is:

- The streak plate and to a lesser extent

- The pour plate.

• Both methods rely on dilution of bacterial cells in a sample to the point at which a single cell can divide giving rise to a single pure colony.

Streak Plate technique(Quadrant Streak, loop dilution)

Types of streaking

Pour plate technique• one loopful from the mixed culture

is transferred between 3 tubes contain nutrient agar(wormed to 50C degree) .

• then poured to plates and allowed to solidify and then incubated.

melted nutrient agar

Lab Exercise Streak plate method

What is required for pure culture?

• Sterile apparatus• Aseptic technique• Appropriate media

Step 1:Do the initial inoculation then FLAME the loop, let cool about 15 seconds.

Step 2: Use the sterile cooled loop and draw over the agar surface in the first section, flame and cool.

Step 3: Use the sterile cooled loop and draw of the agar surface in the second section. Note that you overlap with the first section a few times. Flame the loop and allow to cool.

Step 4. Use the sterile cooled loop and draw of the agar surface in the third section. Again overlap with the second section only. Now flame loop.

Step5. place the plate in incubator.

Isolated Colonies