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Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. [1] The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884. [2]
Starch is a substance common to most plant cells and so a weak iodine solution will stain starch present in the cells. Iodine is one component in the staining technique known as Gram staining, used in microbiology. Used as a mordant in Gram's staining, iodine enhances the entrance of the dye through the pores present in the cell wall/membrane.
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is used by microbiologists to place bacteria into two main categories, Gram-positive (+) and Gram ...
Some, such as Mycobacteria, can be stained with the Gram stain, but they do not take the crystal violet well and thus appear light purple, which can still potentially result in an incorrect gram negative identification. [3] The most common staining technique used to identify acid-fast bacteria is the Ziehl–Neelsen stain, in which the acid ...
This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear weakly Gram-positive. [3] Acid-fast stains such as Ziehl–Neelsen, or fluorescent stains such as auramine are used instead to identify M. tuberculosis with a microscope.
In Berlin, in 1884, Gram developed a method for distinguishing between two major classes of bacteria. [1] This technique, known as Gram staining, continues to be a standard procedure of medical microbiology. This work gained Gram an international reputation. The staining method later played a major role in classifying bacteria. Gram was a ...
Gram-negative bacteria will stain a pink color due to the thin layer of peptidoglycan. If a bacteria stains purple, due to the thick layer of peptidoglycan, the bacteria is a gram-positive bacteria. [4] In clinical microbiology numerous other staining techniques for particular organisms are used (acid fast bacterial stain for mycobacteria).
Appearance of C. xerosis colonies on blood agar. Corynebacterium xerosis is a gram-positive, rod-shaped bacterium in the genus Corynebacterium.Although it is frequently a harmless commensal organism living on the skin and in the mucous membranes, C. xerosis is also a clinically relevant opportunistic pathogen that has been attributed to many different infections in animals and humans.