- Streaking is a microbiology technique.
- Streaking technique used for single cell colonies identification.
- Bacteria and fungi to grow on a semi solid surface to produce decrease colonies.
- Isolate the single species of microorganism.
- Large concentration of bacteria to small concentration of bacteria.
- Robert koch is isolated this technique.
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Types of
streaking
1. T- streak (Three Sector Streak)
2. Zigzag streak
3. Quadrant streak
4. Ecometry streak
T-Streaking:
Three Sector Streak (t streak):
- Sterilize the wire loop.
- Cool the loop by touching it on the edge of the sterile agar plate.
- Dip the loop into the broth culture containing the mixture of bacteria.
- Lift the lid of the plate just enough to insert the loop. Drag the loop over the surface of the top one-third of the plate back and forth in a "zig-zag" formation.
- The loop has picked up thousands of bacteria which are spread out over the surface of the agar.
- Sterilize the loop in the flame.
- Turn the plate 90 degrees and drag the loop through the area you have just streaked two to three times and continue to drag the loop in a "zig-zag" formation in the remaining half of the plate without touching that area again.
- Sterilize the loop in the flame.
- Turn the plate 90 degrees. Repeat the procedure. Drag the loop two to three times through the area you just streaked, and fill in the remaining area of the plate (zig-zag formation), being very careful not to touch any of the areas you previously streaked.
- Incubate the plate for 24 hours. If you streaked correctly, you will see isolated colonies in the third sector. The heaviest growth will be in the first sector. There will be less growth and some isolated colonies in the second sector. The third area should have the least growth with isolated colonies.
Four Quadrant Streak :
- Loosen the cap of the bottle containing the inoculum.
- Hold an inoculation loop in your right hand.
- Flame the loop and allow it to cool.
- Lift the test tube containing the inoculum with your left hand.
- Remove the cap/ cotton wool plug of the test tube with the little finger of your right hand.
- Flame the neck of the test tube.
- Insert the loop into the culture broth and withdraw. At all times hold the loop as still as possible.
- Flame the neck of the test tube again.
- Replace the cap/ cotton wool plug of the test tube using the little finger of your right hand. Place the test tube in a rack. For a liquid culture, dip the loop into the broth, or for solid media, lightly touch a colony with the loop.
- Partially lift the lid of the Petri dish containing the solid medium.
- Place a loopful of the culture on the agar surface on the area 1. Flame the loop and cool it for 5 seconds by touching an unused part of the agar surface close to the periphery of the plate, and then drag it rapidly several times across the surface of area1.
- Remove the loop and close the Petri dish.
- Reflame and cool the loop, and turn the petri dish 90°C then touch the loop to a corner of the culture in area1 and drag it several times across the agar in area 2, hitting the original streak a few times. The loop should never enter area 1 again.
- Remove the loop and close the Petri dish.
- Reflame and cool the loop and again turn the dish 90°C anticlockwise. streak area 3 in the same manner as area 2, hitting last area several times.
- Remove the loop and close the Petri dish.
- Flame the loop, again turn the dish 90°C and then drag the culture from a corner of a area3 across area 4, contacting area 3 several times and drag out the culture as illustrated. Using a wider streak. Do not let the loop touch any of the previously streaked areas. The flaming of the loop at the points indicated is to effect the dilution of the culture so that fewer organisms are streaked in each area, resulting in the final desired separation.
- Remove the loop and close the Petri dish.
- Tape the plate closed and incubates the plate in an inverted position in an incubator for 24-48 hours.
- Flame the loop before putting it aside.
