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Because most capsules are so tightly packed, they are difficult to stain because most standard stains cannot penetrate the capsule. To visualize encapsulated bacteria using a microscope, a sample is treated with a dark stain, such as India ink. The structure of the capsule prevents the stain from penetrating the cell.
Under the microscope, the India ink stain is used for easy visualization of the capsule in cerebral spinal fluid. [10] The particles of ink pigment do not enter the capsule that surrounds the spherical yeast cell, resulting in a zone of clearance or "halo" around the cells. This allows for quick and easy identification of C. neoformans.
The antibody reaction allows these species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge. Photomicrograph of Streptococcus pneumoniae bacteria revealing capsular swelling using the Neufeld quellung test. Notice the two streptococci at the top of the photo that appear to have ...
The Ziehl-Neelsen stain, also known as the acid-fast stain, is a bacteriological staining technique used in cytopathology and microbiology to identify acid-fast bacteria under microscopy, particularly members of the Mycobacterium genus.
A Ziehl–Neelsen stain is an acid-fast stain used to stain species of Mycobacterium tuberculosis that do not stain with the standard laboratory staining procedures such as Gram staining. This stain is performed through the use of both red coloured carbol fuchsin that stains the bacteria and a counter stain such as methylene blue .
Analysis of Mycobacterium tuberculosis via scanning electron microscope shows the bacteria are 2.71 ± 1.05 μm in length with an average diameter of 0.345 ± 0.029 μm. [15] The outer membrane and plasma membrane surface areas were measured to be 3.04 ± 1.33 µm 2 and 2.67 ± 1.19 µm 2, respectively.
Owing to their morphological properties, spirochetes are difficult to Gram-stain but may be visualized using dark field microscopy or Warthin–Starry stain. [35] Examples include: Leptospira species, which cause leptospirosis. Borrelia species, such as Borrelia burgdorferi, a tick-borne bacterium that causes Lyme disease
Mycobacterium smegmatis is an acid-fast bacterial species in the phylum Actinomycetota and the genus Mycobacterium.It is 3.0 to 5.0 μm long with a bacillus shape and can be stained by Ziehl–Neelsen method and the auramine-rhodamine fluorescent method.