Paper 6 1. Ziehl-Neelsen method, its principle, stages. Which properties ensure acid fastness of microorganism? 2. The main structures of prokaryotes. 3 characteristics of different pathogenic spirochetes . Medical significance of spirochetes. Morphology

1. The Ziehl-Neelsen method is a staining technique used to identify acid-fast bacteria. The principle of this method is to differentiate acid-fast bacteria from non-acid-fast bacteria based on their ability to retain the primary stain (carbol fuchsin) after being treated with an acid-alcohol solution. The stages of the Ziehl-Neelsen method are as follows:<br /> - Primary staining: The bacterial smear is stained with carbol fuchsin, a red dye.<br /> - Decolorization: The slide is treated with an acid-alcohol solution, which removes the primary stain from non-acid-fast bacteria.<br /> - Counterstaining: The slide is then stained with a secondary stain, such as methylene blue, which stains the non-acid-fast bacteria.<br /><br />The properties that ensure the acid-fastness of microorganisms are the high lipid content in their cell walls, particularly mycolic acids. These long-chain fatty acids create a waxy, hydrophobic barrier that prevents the primary stain from being easily removed during the decolorization step.<br /><br />2. Prokaryotes are single-celled organisms that lack a true nucleus and membrane-bound organelles. The main structures of prokaryotes include:<br /> - Cell wall: Provides structural support and protection.<br /> - Plasma membrane: Encloses the cell and regulates the movement of substances in and out.<br /> - Cytoplasm: The fluid medium within the cell where metabolic reactions occur.<br /> - Nucleoid: The region where the genetic material (DNA) is located.<br /> - Ribosomes: Sites of protein synthesis.<br /> - Flagella: Long, whip-like structures used for movement.<br /> - Pili: Hair-like structures used for attachment and conjugation.<br /><br />3. Spirochetes are a group of spiral-shaped bacteria. They have unique characteristics that distinguish them from other bacteria. Some of the characteristics of different pathogenic spirochetes include:<br /> - Treponema pallidum: The causative agent of syphilis, a sexually transmitted infection.<br /> - Borrelia burgdorferi: The causative agent of Lyme disease, transmitted through tick bites.<br /> - Leptospira interrogans: The causative agent of leptospirosis, transmitted through contaminated water or soil.<br /><br />The medical significance of spirochetes lies in their role in causing various diseases in humans. These diseases can range from sexually transmitted infections to vector-borne diseases and zoonotic diseases. Proper diagnosis and treatment of these diseases are essential for preventing complications and ensuring public health.