Focus Figure Microbial World Acellular Infectious Organisms agents Domain Bacteria Archaea Eukarya Viruses Viroids Prions Prokaryotes (unicellular) Eukaryotes Algae (unicellular or multicellular) Protozoa Fungi (unicellular or multicellular) Helminths (unicellular) (multicellular parasites) Protists FIGURE 1.6 The Microbial World Although adult helminths (worms) are generally not microscopic, some stages in the life cycle of many disease-causing helminths are.
Microscopic examination
The analysis of minute organisms, cellular organization of any biological structure, and composition of body fluids with the help of a microscope is known as microscopic examination. The magnification of specimens or samples under study helps in attaining a clearer picture of it.
Gram Staining
Named after Hans Christian Gram, a Danish bacteriologist, Gram stain is one of the most powerful staining techniques within microbiology. This technique was introduced in 1882 to identify pneumonia-causing organisms. The Gram staining technique uses crystal violet or methylene blue as primary staining colors to distinguish gram-positive from gram-negative organisms. Under a microscope, the gram-positive organisms appear purple-brown, retaining the primary color. Gram-negative organisms appear pink or red as they do not acquire the color of the primary stain.
The members of which two domains cannot be distinguished microscopically?
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