Streak Plate Technique

Purpose

• Allows isolation of a single colony from a bacterial culture.
• Involves splitting the plate into quadrants.
• Dilutes bacteria by streaking through each quadrant.

Lighting a Bunsen Burner

• Close valve: Rotate the collar to cover the vents.
• Turn on gas: Slowly.
• Ignite burner: Adjust flame height by controlling gas amount.

Flame Temperatures

• Yellow/Orange Flame: Coolest.
• Blue Flame: Medium temperature.
• Roaring Blue Flame: Hottest, characterized by a clear blue cone; the tip is the hottest part.

Sterilizing Inoculating Loop

• Flame the loop: Sterilize.
• Cool the loop: Touch it to an empty spot on the bacterial plate.

Streaking Process

1. Scrape Colony: Lightly scrape colony from the plate surface to collect on the loop.
2. Transfer to LB Agar Plate:
   • Streak: Rub loop back and forth in the top left corner (~10 times).
   • Flame loop: Sterilize.
3. Rotate Plate 45 Degrees:
   • Streak Second Quadrant: Draw loop through one end of the first streak, rub ~10 times.
   • Flame loop: Sterilize.
4. Rotate Plate 45 Degrees Again:
   • Streak Third Quadrant: Draw loop through one end of the second streak, rub ~10 times.
   • Flame loop: Sterilize.
5. Repeat for Fourth Quadrant: Final streaking, then flame loop.

Incubation

• Invert Plate: Place in incubator at 37°C.
• Duration: 24 to 48 hours.

Examination

• After incubation, colonies will have grown and can be examined.