Preparation of Slide of Bacteria from Curd

SLIDE PREPARATION FROM CURD

Curd Sample Smear Preparation and Gram Staining

INTRODUCTION

Curd is a milk product formed by fermentation. Fermentation is the activity of a genus of bacteria named as Lactobacillus. Lactobacillus bacteria convert sugars into lactic acid by means of fermentation. Milk contains a sugar called lactose, a disaccharide (compound sugar) made by the glycosidic bonding between glucose and galactose (monosaccharide). Curd contains different types of bacteria such as cocci, bacillus etc. By Gram staining method a differential stain is used for demonstration of Gram positive and Gram negative bacteria. The Method for staining bacteria is as under:

METHOD FOR PREPARATION OF SLIDE OF BACTERIA

1. Take a grease free glass slide and draw a thin smear of curd sample with the help of another slide.

2. Heat fix the smear.

3. Now put a few drops of crystal violet and keep it for 2 minutes.

4. Next wash the slide with tap water.

5. After washing put few drops of Gram's Iodine on the smear and keep it for 2 minutes.

6. Wash again with tap water.

7. Then put few drops of Safranine on the smear and keep it for 1 minute and wash.

8. Observe under compound microscope.

                                    Figure: Gram Positive and Gram Negative Bacteria

OBSERVATIONS

1.      Gram Positive Cocci:      Color-Purple

2.      Gram Negative Bacilli:   Color-Red