Question

Streak Plate

Drawing or Picture of Plate Description of colonies/plate:

Gram Stain

Draw and color Gram reaction, size, shape/arrangement:

(what you see under microscope)               

Identification of: Serratia marcescens

1)STREAK PLATE OF Serratia marcescens

2)RESULTS OF STREAK PLATE:

A: Explain the Gram reaction, size, shape, and arrangement you would expect to see after performing these procedures of your bacteria.

*Draw what your streak plate would look like on your worksheet.

B: What would a successful streak look like? What could be improved upon if you were to redo it after an unsuccessful attempt?

*Draw and color the gram stain result, the cells shape and arrangement.

Answer 1

1) Streaking:

• A pure culture is a culture of a single strain of organism, without the contamination from other strains of organisms. For isolation of pure culture, techniques used can be like straking.
• Streaking- It involves various streaking patterns using sterile loop, with thinning out of the inoculum, at end of a streak.
• For Serratia macescens, red colonies will be observed at the fourth quadrant of streaking.

2) Gram staining:

• Gram staining procedure uses stains to distinguish Gram positive bacteria from Gram negative.
• The thicker peptidoglycan layer forms complex with primary stain crystal violet and mordant Gram’s Iodine, along with heat fixing. This stain is retained even during the decolorization phase with alcohol.
• While cells with thinner peptidoglycan layer cannot retain primary stain, after decolorization and take up the secondary stain Safranin.

Serratia macescens appears as: Gram negative (Red colored) bacilli (rod shaped).