Microbiology glossary, terms and definitions from A

Microbiology glossary, terms and definition from A
Microbiology glossary, terms, and definition from A. Created with BioRender.com

Microbiology terms and definitions from A

AB toxins definition

  • Bacterial exotoxins consisting of two polypeptides. (Microbiology: An Introduction by Tortora, Funke, and Case)
  • Exotoxins composed of two parts (A and B). The B portion is responsible for toxin binding to a cell but does not directly harm it; the A portion enters the cell and disrupts its function. (Prescott’s Microbiology)

ABC (ATP-binding cassette) transporter definition

  • A membrane transport system consisting of three proteins, one of which hydrolyzes ATP, one of which binds the substrate, and one of which functions as the transport channel through the membrane. (Brock Biology of Microorganisms)

Abiogenesis definition

  • The belief in spontaneous generation as a source of life. (Foundation in Microbiology by Talaro and Chess)

Abiotic definition

  • Nonliving factors such as soil, water, temperature, and light that are studied when looking at an ecosystem. (Foundation in Microbiology by Talaro and Chess)

ABO blood group system definition

  • Developed by Karl Landsteiner in 1904; the identification of different blood groups based on differing isoantigen markers characteristic of each blood type. (Foundation in Microbiology by Talaro and Chess)
  • The classification of red blood cells based on the presence or absence of A and B carbohydrate antigens. (Microbiology: An Introduction by Tortora, Funke, and Case)

Abscess definition

  • A circumscribed pus-filled lesion characteristic of staphylococcal skin disease; also called a boil. (Alcamo’s Fundamentals of Microbiology)
  • A localized infection characterized by the production of pus. (Brock Biology of Microorganisms)
  • An inflamed, fibrous mass enclosing a core of pus. (Foundation in Microbiology by Talaro and Chess)
  • Localized accumulation of pus. (Microbiology: An Introduction by Tortora, Funke, and Case)

Abyssal zone definition

  • The environment at the bottom of the oceanic trenches. (Alcamo’s Fundamentals of Microbiology)
  • The deepest region of the ocean; a sunless, high-pressure, cold, anaerobic habitat. (Foundation in Microbiology by Talaro and Chess)

Abzyme definition

  • Abzyme is defined as a monoclonal antibody that has catalytic activity. (Kuby Immunology)

Acetyl CoA (Acetyl-Coenzyme A) definition

  • One of the starting compounds for the Krebs cycle. (Alcamo’s Fundamentals of Microbiology)
  • A molecule made of acetic acid and coenzyme A that is energy-rich; it is produced by many catabolic pathways and is the substrate for the tricarboxylic acid cycle, fatty acid biosynthesis, and other pathways. (Prescott’s Microbiology)

Acid definition

  • A substance that releases hydrogen ions (H+) in solution. (Alcamo’s Fundamentals of Microbiology)
  • A substance that dissociates into one or more hydrogen ions (H+) and one or more negative ions. (Microbiology: An Introduction by Tortora, Funke, and Case)

Acid-fast stain definition

  • A staining process in which mycobacteria resist decolorization with acid alcohol. (Alcamo’s Fundamentals of Microbiology)
  • A property of Mycobacterium species; cells stained with basic fuchsin dye resist decolorization with acidic alcohol. (Brock Biology of Microorganisms)
  • A term referring to the property of mycobacteria to retain carbol fuchsin even in the presence of acid alcohol. The staining procedure is used to diagnose tuberculosis. (Foundation in Microbiology by Talaro and Chess)
  • A differential stain used to identify bacteria that are not decolorized by acid-alcohol. (Microbiology: An Introduction by Tortora, Funke, and Case)
  • A staining procedure that differentiates between bacteria based on their ability to retain a dye when washed with an acid alcohol solution. (Prescott’s Microbiology)

Acidic definition

  • A solution with a pH value below 7 on the pH scale. (Foundation in Microbiology by Talaro and Chess)

Acidic dye definition

  • A negatively charged colored substance in a solution that is used to stain an area around cells. (Alcamo’s Fundamentals of Microbiology)
  • A salt in which the color is in the negative ion; used for negative staining. (Microbiology: An Introduction by Tortora, Funke, and Case)

Acidophile definition

  • A microorganism that grows at acidic pHs below 4. (Alcamo’s Fundamentals of Microbiology)
  • An organism that grows best at acidic pH values. (Brock Biology of Microorganisms)
  • A bacterium that grows below pH 4. (Microbiology: An Introduction by Tortora, Funke, and Case)
  • A microorganism that has its growth optimum between about pH 0 and 5.5. (Prescott’s Microbiology)

Acquired immune response definition

  • The acquired immune response is the immunity mediated by lymphocytes and characterized by antigen-specificity and memory. (Roitt’s Immunology)

Acquired Immunodeficiency Syndrome (AIDS) definition

  • Acquired Immunodeficiency Syndrome (AIDS) is defined as a disease caused by the human immunodeficiency virus (HIV) that is marked by significant depletion of CD4+ T cells and that results in increased susceptibility to a variety of opportunistic infections and cancers. (Kuby Immunology)

Activation-induced cytidine deaminase (AID) definition

  • Activation-induced cytidine deaminase (AID) is defined as an enzyme that removes an amino group from deoxycytidine, forming deoxyuridine. This is the first step in the processes of both somatic hypermutation and class switch recombination. (Kuby Immunology)

Active immunity definition

  • Active immunity is defined as an adaptive immunity that is induced by natural exposure to a pathogen or by vaccination. (Kuby Immunology)

Acute lymphocytic leukemia (ALL) definition

  • Acute lymphocytic leukemia (ALL) is defined as a form of cancer in which there is an uncontrolled proliferation of a cell of the lymphoid lineage. The proliferating cells usually are present in the blood. (Kuby Immunology)

Addressin definition

  • Addressin is defined as the cell adhesion molecule present on the luminal surface of blood and lymph vessel endothelium and recognized by homing molecules that direct leukocytes to tissues with the appropriate “address.” (Roitt’s Immunology)

Antibody definition

  • The antibody is defined as the proteins consisting of two identical heavy chains and two identical light chains, that recognize a particular epitope on an antigen and facilitates clearance of that antigen. The membrane-bound antibody is expressed by B cells that have not encountered antigen; secreted antibody is produced by plasma cells. Some antibodies are multiples of the basic four-chain structure. (Kuby Immunology)

Antigen definition

  • The antigen is defined as any molecule capable of being recognized by an antibody or T-cell receptor. (Roit Immunology)
  • The antigen is defined as any substance (usually foreign) that binds specifically to an antibody or a T-cell receptor. (Kuby Immunology)

References and Sources

  1. Alcamo’s Fundamentals of Microbiology
  2. Brock Biology of Microorganisms
  3. Foundation in Microbiology by Talaro and Chess
  4. Microbiology: An Introduction by Tortora, Funke, and Case
  5. Prescott’s Microbiology

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