Have you ever wondered how scientists distinguish between different types of bacteria under microscopes? One of the most essential techniques in microbiology and in any lab is gram staining. Gram staining was a method that was developed by Hans Christian Gram in 1884. Although the procedure is simple and fun for most, it is a very powerful procedure that separates bacteria into gram-positive and gram-negative groups based on their cell wall composition.
Why Gram Staining?
Bacteria have different cell wall structures which determines how they interact with the stains. Gram-positive bacteria have a thick peptidoglycan
layer which retains the primary stain and appears purple under the microscope. Gram-negative bacteria have a thin peptidoglycan layer In addition to an outer membrane which causes them to lose the primary stain and take up the counterstain which is pink or red. The distinction between these two colors is critical especially for diagnosing infections and select antibiotics.
How Does It Work?
Gram staining is not a lengthy procedure and can be quite enjoyable.First a drop of water is placed on a clean glass slide. A sterile loop is used to transfer a small amount of bacteria and is mixed with the water and spread into a thin film .Once the slide is air dried the slide is passed through a flame two to three times to kill and fix the bacteria onto the slide. Heat fixation is an important step during staining because it allows the sample to adhere to the slide and kill the bacteria. Four components are added to the slide one by one first Crystal violet then grams iodine following ethanol and finally safranin. Once each stain is added to the sample, individually, It stays on the slide for about 1 minute and then rinsed with distilled water. It is important to know that ethanol is added drop by drop and only for 5 to 10 seconds until the runoff is clear because if ethanol is left on for too long it can decolorize gram-positive cells which can lead to inaccurate results. After this procedure the slide is ready to be placed on a microscope and observe the bacteria sample.
Something Interesting
In June 2023 researchers at Baylor College of Medicine published a study in Science Daily detailing a novel approach to combat antibiotic resistance. Researchers identified that dequalinium chloride (DEQ) can significantly reduce the rate at which Escherichia coli develops resistance when exposed to an antibiotic called ciprofloxacin. DEQ functions by inhibiting stress responses in bacteria that increase mutation rates leading to resistance. The co-administration of DEQ with ciprofloxacin resulted in a marked decrease in the emergency of resistant bacterial strains in both laboratory cultures and animal models, This suggests that similar compounds could be utilized with existing antibiotics to prolong their efficiency by slowing down the bacterial evolution of resistance,
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