Applying a Simple Stain to a Bacterial Culture

Applying a Simple Stain to a Bacterial Culture


APPLYING A SIMPLE STAIN TO A BACTERIAL CULTURE
IS A TECHNIQUE THAT IS USED FOR EXAMINING THE SIZE, SHAPE, AND ARRANGEMENT OF A SPECIMEN. IT USES A DYE TO STAIN THE CELLS, MAKING THEM
EASIER TO SEE UNDER A MICROSCOPE. IN THIS EXPERIMENT, WE WILL DEMONSTRATE THE
STEPS FOR APPLYING A SIMPLE STAIN TO THE BACTERIAL ORGANISM, STAPHYLOCOCCUS. START WITH A CLEAN MICROSCOPE SLIDE. USE A CHINA-MARKING PENCIL TO LABEL ONE END
OF THE SLIDE WITH THE SPECIMEN NAME. DRAW A CIRCLE IN THE CENTER OF THE SLIDE. BECAUSE WE’RE USING STAPHYLOCOCCUS FROM
A SOLID SOURCE, WE’LL DRAW A CIRCLE ABOUT THE SIZE OF A NICKEL. TURN THE SLIDE OVER SO THAT THE CIRCLE IS
ON THE BOTTOM. THIS WILL PREVENT THE MARKING FROM MIXING
IN WITH THE SAMPLE. ADD A DROP OF DISTILLED WATER TO THE SLIDE. STERILIZE AN INOCULATING LOOP BY PASSING IT
THROUGH THE FLAME OF A BUNSEN BURNER. WHEN THE LOOP IS COOL, TOUCH THE BACTERIAL
COLONY AND TRANSFER THE BACTERIA TO THE SLIDE. USE THE LOOP TO MIX THE CELLS AND THE WATER. SPREAD THE MIXTURE TO COMPLETELY FILL THE
CIRCLE. ALLOW THE SLIDE TO AIR DRY AT ROOM TEMPERATURE. THE TIME WILL VARY DEPENDING ON THE SIZE OF
THE SMEAR. YOU WILL KNOW THE SLIDE IS DRY WHEN YOU SEE
A THIN WHITE HAZE. NEXT, HEAT-FIX THE SLIDE BY PASSING IT THROUGH
A FLAME THREE TIMES. FLOOD THE SLIDE WITH SAFRANIN. SAFRANIN IS A BIOLOGICAL STAIN THAT WILL DYE
THE BACTERIAL CELLS RED, MAKING THEM EASIER TO SEE UNDER A MICROSCOPE. BE SURE TO FILL THE ENTIRE CIRCLE WITH THE
DYE. LEAVE THE STAIN ON FOR 30 SECONDS. GENTLY WASH THE SLIDE WITH DISTILLED WATER. DRAIN OFF ANY EXCESS WATER. USE BIBULOUS PAPER TO GENTLY BLOT THE SLIDE
DRY. AFTER THE SLIDE HAS COMPLETELY AIR-DRIED,
THE SMEAR WILL LOOK LIKE A THIN RED HAZE. HERE YOU CAN SEE THE DIFFERENCE. THE SLIDE ON THE LEFT IS OUR STAINED SLIDE. THE SLIDE ON THE RIGHT IS UNSTAINED. LOAD THE STAINED SLIDE ONTO THE MICROSCOPE
STAGE. ALWAYS START WITH THE LOWEST POWER OBJECTIVE. USE THE COURSE AND FINE ADJUSTMENTS TO BRING
THE BACTERIA INTO FOCUS. SINCE THIS IS A BACTERIAL SPECIMEN WE MUST
OBSERVE IT UNDER OIL IMMERSION. THE STAPHYLOCOCCUS CELLS LOOK LIKE SMALL RED
BALLS. SKETCH THE IMAGE IN YOUR LAB NOTEBOOK. NOW YOU’RE READY TO GO INTO THE LAB AND
PERFORM A SIMPLE STAIN.

Author: Kennedi Daugherty

12 thoughts on “Applying a Simple Stain to a Bacterial Culture

  1. This is an excellent video that includes all the steps to performing a simple stain including pictures of the speicmen at each magnification including oil immersion. Like the video said…"Now I am ready to go into the lab and perform a simple stain." Thanks!

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