Gram stain bacteria pdf

The gram stain is a differential stain commonly used in the microbiology laboratory that differentiates bacteria on the basis of their cell wall structure. The gram stain technique basic protocol is a differential staining technique since it reacts differently with different types of bacteria based on their cell wall. Pdf gram staining is an empirical method of differentiating bacterial. The gram stain ranks as one of the most important stains for bacteria. The name comes from the danish bacteriologist hans christian gram, who developed the technique. Failure to follow these directions may cause staining artifacts and disrupt the normal morphology of bacteria and cells. How to prepare a bacterial smear for gram stain stepby. A bacterium is referred as a protoplast when it is without cell wall.

The gram stain procedure distinguishes between gram positive and gram negative groups by coloring these cells red or violet. Available in colors other dyes that preferentially stain gram positive bacteria include membrite fix and calcofluor white surface stains, nucspot live dna stains. Interpretation of gramstained smears involves consideration of staining. Stain dark purple due to retaining the primary dye.

Slides are sequentially stained with crystal violet, iodine, then destained with alcohol and counterstained with safranin. Bacterial classification, structure and function columbia university. Grampositive bacteria thick layer of peptidoglycan90% of cell wall stains purple. This cell is easily lysed and it is metabolically active but unable to reproduce. The gram stain is used to classify bacteria on the basis of their forms, sizes. Fluorescent gram stains wheat germ agglutinin wga is a carbohydratebinding lectin that preferentially binds to gram positive bacteria fig. Using a solvent to remove the stain from some types of bacteria. Gram staining is still the cornerstone of bacterial identification and taxonomic division. Some staining techniques, such as the gram and ziel neelsen stains, although of great diagnostic value because of their differential staining properties for specific bacteria, reveal little internal structure. In the gram stain, an insoluble crystal violetiodine complex is formed inside the cell, and this complex is extracted by alcohol from gramnegative but not from grampositive bacteria.

The smear is then stained with crystal violet dye, which is rinsed off and replaced with an iodine solution. In a similar way as in acidfast, in the gram stain, a bacterial smear is dried and then heatfixed to denature the cell proteins and to cause bacteria to adhere to the glass slide. This differential staining procedure separates most bacteria into two groups on the basis of cell wall composition. The gram stain is used to classify bacteria on the basis of their forms, sizes, cellular morphologies, and gram reactions.

Learn what it involves and when your doctor might order it. Gram positive bacteria stain bluepurple and gram negative bacteria stain red. Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. A gram stain is a test used to learn if bacteria are present in your body fluids or tissue. These bacteria with a thin cell wall are counterstained with safranin and are labeled as the gramnegative bacteria.