Principle of Acid-Fast Staining: Acid-fast staining identifies bacteria with waxy cell walls containing mycolic acids, which do not readily take up stains but retain certain dyes even after being washed with acid-alcohol. This is particularly useful for identifying Mycobacterium species. Procedure of Acid-Fast Staining: Preparation of Smear and Fixation: As in simple staining. Primary Stain: … Read more

Principle of Gram Staining: Gram staining differentiates bacteria based on the structure of their cell walls. Gram-positive bacteria retain the primary stain, while Gram-negative bacteria do not, due to differences in their cell wall composition. Procedure of Gram Staining: Preparation of Smear and Fixation: As in simple staining. Primary Stain: Crystal violet is applied to … Read more

Principle of Scanning Electron Microscopy (SEM) SEM scans a focused electron beam across the specimen’s surface. Secondary electrons emitted from the specimen surface are collected to form an image. SEM provides high-resolution, three-dimensional images that reveal the specimen’s surface topology. Procedure for Scanning Electron Microscopy (SEM) Specimen Preparation: Fixation: The specimen is fixed to preserve … Read more

Principle of Simple Staining: Simple staining involves using a single dye to color bacterial cells, making it easier to observe their shape, size, and arrangement under a microscope.   Procedure: Preparation of Smear: A small sample of bacteria is spread on a microscope slide to form a thin film and then air-dried. Fixation: The slide … Read more

Quantitative Measurement of Bacterial Growth involves measuring either the total cell counts or the viable cell count. Total Cell Count Methods Counter Chamber Method (Hemocytometer) Description: A manual counting method using a specialized slide with a grid. Procedure: A known volume of bacterial suspension is placed on the hemocytometer grid. The grid is viewed under … Read more

Phase contrast microscopy is a technique that enhances the visibility of transparent and colorless specimens by converting subtle differences in the optical path length (caused by variations in refractive index and thickness) into variations in contrast. This allows for the observation of live, unstained cells, making internal structures visible without damaging or altering the specimen. … Read more

Electron microscopy offers much higher resolution than light microscopy by using electron beams instead of light. There are several types, each with unique principles and advantages. Types of Electron Microscopy: Transmission Electron Microscopy (TEM): Electrons pass through a thin specimen. Provides detailed images of internal structures. Scanning Electron Microscopy (SEM): Electrons scan the specimen surface. … Read more

Dark field microscopy enhances the contrast of transparent and unstained specimens by illuminating them with light that does not enter the objective lens unless it is scattered by the specimen. This creates a bright image of the specimen against a dark background, making normally invisible structures visible. Procedure for Dark Field Microscopy Preparation of the … Read more

Principle of Transmission Electron Microscopy  Transmission Electron Microscopy works by transmitting a beam of electrons through an ultra-thin specimen. As electrons interact with the specimen, the transmitted electrons form an image. Due to the short wavelength of electrons, TEM can resolve details as small as 0.1 nm, making it suitable for studying cellular ultrastructure and … Read more