Question

Describe the microscopic techniques required to view Gram stains. What can information can be gathered by using the low power objective? What information can be gathered by using the oil immersion lens?

Answer 1

Microscopic techniques required to view gram stains

Gram staining is largely used to differentiate bacteria species as either gram negative or positive. This is achieved through the chemical Properties of bacterial cell walls where different colors are displayed after staining.

Techniques

1. ​​​​Application of crystal violet purple dye.

2.Application of mordant iodine, which fixes stain

3.Slide is washed with alcohol,

gram positive bacteria retains crystal violet Iodine stain, whereas gram negative bacteria lose the stain. The gram negative bacteria subsequently stained with safranin dye, counterstain next. These bacteria appear red under the oil immersion lens, while gram positive bacteria appear blue or purple reflecting the crystal violet retained during the washing step.

Low power objective

It covers wide field of review and they are useful for examining large specimens or surveying many small specimens. Power of low objective is 10x.

oil immersion lens

Placing a drop of oil with the same refractive index between cover slip and objective lens eliminate two refractive surfaces, so that magnification of 1000x can be achieved while still preserving good resolution.

What information can be gathered by using the oil immersion lens

• This technique is used when we can view specimen that is no thicker than few Micrometers
• Essential for viewing individual bacteria and striations of skeletsl muscles
• It is best for viewing samples that are dead and not moving
• Very small moving protist can be viewed but this technique heavily used for viewing dead or no motile specimen.