In: Biology
histology and microscopy, what are the steps required to view bacteria samples using a compound microscope?
Question a
How to select the bacteria cultures for vviewing?
When inoculated into a culture media, bacterial growth follows a definite course.The bacterial growth curve has four phases-lag phase,log phase,stationary phase and phase of decline.In the log phase, bacteria multiply exponentially and growth curve take the shape of a straight line. It is this phase which is ideal for performing Gram stain.In this phase,bacteria will be uniformly stained.If Gram stain is performed during the stationary phase,bacteria will appear as Gram variable. But storage granules and spores are better visible during this phase.Young actively growing cultures are used for performing Gram staining.Q
question b
Question c
How to set up the compound microscope
For low power ,settings are 10x objective, iris diaphragm fully closed, condenser fully lowered
For high power,settings are 40x objective, iris diaphragm half open,condenser half raised
For oil immersion, setting are 100x objective, iris diaphragm fully opened,condenser fully raised
Microscope should be protected from direct heat and light.After use it should be kept covered using a cover.Lenses should be kept clean from dust and dirt.For cleaning xylene is used,alcohol should not be used.
The steps for observing bacteria under microscope are
Preparing smear
Air drying
Fixation of smear
Staining
Microscope adjustments