Microbiology lab report: Negative staining of staphylococcus aureus

MICROBIOLOGY MB102b

LAB REPORT #3:

Negative staining of Staphylococcus aureus with nigrosin

Muhammed Sayed Hassan ID: 171741 GROUP (F)

Submitted to: L.A. Suzanne L.A.  Suzanne ali

Negative staining of Staphylococcus aureus with nigrosin INTRODUCTION

This lab covered smear preparation of staphylococcus aureus on the microscopic slide with the heat fixation method, Then negative staining with acidic dye (Nigrosin) and successfully identifying it's shape under the light microscope. The negative staining method depends on the repulsion of the bacterial cell surface of the negative charged dye to colorize the background(microscopic slide). Aim of the lab is to negative stain staphylococcus aureus and identify it's shape under the light microscope.

MATERIALS

Chemical agents: 1. Immersion oil 2. Nigrosin (Nigrosin 100 gm/L, Formalin 5 ml/L in water) 3. Distilled water 4. Ethanol (70%)

Biological agents: 1. Staphylococcus aureus

Equipments: 1. Light Microscope 2. Microscopic slide 3. Aluminium foil sheet 4. Inoculation loop 5. Bunsen burner

1

PROCEDURE a)  Smearing of bacteria 1. 1 drops of water was put on the microscopic slide. 2. The inoculation loop was sterilized by bunsen burner. 3. 1 loopful was put on the microscopic slide. 4. The bacteria was smeared on the slide.

b)  Heat fixation of bacteria 5. The bacteria was heated with bunsen burner with indirect flame fixation.

c) Negative staining of the slide 6. The microscopic slide was put on the aluminium foil sheet. 7. 2 drop of dye were dropped on the edge of the microscopic slide. 8. Another slide was used at angle of 45° to smear the dye carefully on the bacteria slide. 9. Then the slide was drought for about 10 minutes before examination.

d)  Microscopic examination of the slide 10. 1 drop of immersion oil was dropped on the slide. 11. The slide was put in the microscopic clip. 12. Knob was zoomed until the lens touched the oil concave surface. 13. Then the slide was examined with the Oil lens.

2

RESULTS

Fig(1): Negative stain of staphylococcus aureus bacteria shown under a light microscope Using Oil-immersion technique.

DISCUSSION Above fig(1) shows that cultured staphylococcus aureus under light microscope using oil-immersion lens. Smear and negative staining was successfully applied, the background of the slide had the dye but the bacterial cell surface repulsed the dye because it's acidic and has a negative charges as the surface of the bacterial cell.

CONCLUSION The aim of the lap was successfully achieved which is negative staining of staphylococcus aureus using nigrosin acidic dye.

3