![]() A decolouriser such as acetone or methanol is then added to attempt to remove these large complexes from the cell.Iodine is then added, which forms large molecular complexes with crystal violet.Initially, positively charged crystal violet is added to the cells, which binds to negatively charged cell components.Shutterstock, licensed to TeachMeSeries Ltdįig 1 – Structural difference between gram-positive and gram-negative bacteria Gram-Staining Techniqueīy understanding the technique used during Gram-staining, it can help you to remember which colours represent gram-positive and gram-negative organisms respectively. Not all bacteria can be gram-stained – Mycobacterium tuberculosisis the causative organism of tuberculosis and is considered gram-indeterminate. Gram-staining separates bacteria into Gram-positive and Gram-negative organisms, depending on the thickness of peptidoglycan present in the cell wall Gram-positive bacteria have a thick layer of peptidoglycan, whereas Gram-negative have a thin layer. The stain is named after a microbiologist Hans Christian Gram, and has nothing to do with the measure of mass (g). The second way of classifying bacteria is according to Gram-staining. An example of is Treponema pallidum, the causative organism of syphilis. Spirochaete: These are tightly coiled.Vibrios: Flagellated (tailed) organisms, a notable example of which is Vibrio cholerae, the causative organism of cholera.Spirilla: Spiral-shaped bacteria, although these are less common.Cocci: These spherical micro-organisms are found grouped together, as staphylococci (clusters), streptococci (lines) or diplococci (paired).Bacilli: Also known as rods, these are long and thin.Classification Shapeīacteria can be classified simply by their shape. ![]() Bacteria are prokaryotic micro-organisms/pathogens and along with viruses, account for the majority of infectious diseases in humans. ![]()
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