Microbiology terms - A
- ABO blood group
- Classification of red blood cells based on the presence or absence of A and B carbohydrate
- A localized accumulation of pus due to infection.
- acellular vaccine
- Vaccine consisting of antigenic parts of cells.
- The process of splitting acetate into methane and carbon dioxide by s ome methanogens.
- acetyl-CoA pathway
- A pathway of autotrophic carbon dioxide fixa tion commonly happened in obligate anaerobes
such as methanogens
- , homoacetogens, and sulfate-reducing bacteria.
- acetylene reduction assay
- A method to determine the activity of nit rogenase. Instead of the natural substrate of
nitrogenase, i.e. dinitrogen (N2), acetylene is provide d as the alternative substrate for this
enzyme . Acetylene (C2H2) is reduced to ethylene (C2 H4) during the assay if there is
nitrogenase activity. B oth substrate and product can be resolved by gas chromatography.
- acid mine drainage
- The process to draw off acidic water from natural mine rich of sulfid e minerals which has
been oxidized to sulfuric acid by microbial actions.
- acid-fast stain
- A staining technique used to determine the cell wall property of an m icroorganism. After
stained with dye such as hot carbolfuschin, an acid-f ast organism, (.e.g. Mycobacterium
species) will retain the color in its cell wall after being washed with acid-alcohol.
- An organism that grows optimally at acidic (low) pH values (usually b elow 6, sometimes as
low as 1) and grows poorly or not at all under highe r pH conditions (i.e. higher than 7).
- Gram-positive bacteria that can for m branching filaments. They may form true myceli a or
- activation energy
- Energy required to make substrate molec ules active enough for an reaction to occur.
Catalysts and enzymes function by lowering the activation energy of the su bstrates during a
- A regulatory protein that binds to specif ic sites on DNA and stimulates transcription; an
activator is usually involved in the po sitive control of transcription regulation.
- active immunity
- Production of antibodies by the body's own im mune system due to the exposure to antigen.
Compare with passive immunity.
- active site
- The region of an enzyme where substrate(s) bind(s) prior to the reaction occurs.
- active transport
- The energy-dependent process of transporting substances (e.g. nutrien ts, ions, waste
products) into (uptake) or out of (efflux) the cell in which the transported substances are
chemically un changed.
- Used to describe a short-term infection or disease which is characterized by dramatic onset
and rapid recovery.
- Refers to the ability of bacteria adhea r (stick) to host surfaces.
- aerobe (adjective: aerobic)
- An organism that grows in the presence of oxygen. There may be facultative or obligat e
aerobes. Compare with anaerobe.
- An adjective used to describe an environment or a condition in which oxygen (O2) is present;
an adjective to describe an organism w hich can grow in the presence of oxygen.
- gas producing, e.g., aerogenic fermentation.
- A gaseous suspension of fine solid or liquid particles. In medical as pect, An aerosol released
by sneezing or coughing, may contain viable mic robial particles such as microorganisms or
- Used to describe an anaerobe which will not be inhibited by oxygen and can still grow at
- A complex polysaccharide which is widely used as a gelling agent used to prepare solid or
semi-solid microbiological medium. Agar consists of about 70% of agarose and 30% of
agaropectin. Agar can be melt at temperature above 100°C; gelling temperature is 40-50°C.
Also called: agar agar.
- A non-sulphated linear polymer consisting of alternating residues of D-galactose and
Agarose is extracted from seaweed and is widely used as the resolving agent in
electrophoresis (i.e. agarose gel electrophoresis).
- Aggregation formed by the combination of antibody and particle-bound antigen.
- alga (plural algae)
- Phototrophic eukaryotic microorganisms. Algae c ould be unicellular or multicellular.
Blue-green algae is not true algae; it belongs to a group of bacteria called c yanobacteria
because it lacks a nucleus i n the cell.
- alkaliphile (also alkalophile)
- An organism that grows optimally at high pH (alkaline conditions). Th e typical pH range for
alkaliphiles is 8 - 11. They grow poorly or not at all at the pH below 7. Compare with
- A harmful immune reaction, either immediat e-type or delayed-type hypersensitivity caused
by a foreign antigen (i.e. allergen) i n food, pollen, or chemicals.
- Used to describe some protein, especially enzymes, in which a compound combine with a
site on the protein other than the active site. This may result in a conformational change at the
active site so that the normal substrate can not bind to it. The a llosteric property is useful in
the regulatiio n of enzyme activity.
- amber mutation
- The mutation due to the introduction of a stop codon (UAG) within the coding sequence of a
gene which results in premature termination of translation.
- amino acid
- An organic acid containing an amino group (-NH2) and a carboxyl group (-COOH). Can be
represented by the general formula: R-CH(NH2)COOH, in which R may be hydrogen or an
organic group and determines the properties of the amino acid. Amino acids are building
blocks of proteins.
- amino group
- amoeba (or ameba, plural: amoebae)
- Refers to any (eukaryotic) cell or orga nism which is able to alter its cell shape drastically,
usually by the ex trusion of one or more pseudopodia.
- A genus of free-living amoebae. Type species: Amoeba proteus.
- amoeboid movement
- A type of motility in which cytoplasmic streaming extrudes outward of the cell to form
pseudopodia) so that the cell can be relocated.
- 1. Increase of copy number of a plasmid by inhibiting the replication of chromosome while
allowing plasmid replication to continue.
2. Increase of the number of copies of a gene either by duplication in the chromosome or by
cloning into a plasmid vector. This is normally referred to as gene amplification.
- Refers to those metabolic processs involved in the synthesis of cell constituents from simpler
molecules, such as org anic and/or inorganic precursors. An anabolic process usually requires
- An organism which has the ability to grow in the absence of oxygen. C ompare with aerobe.
Also see facultative anaerobe.
- An adjective used to describe an environment or a condition which is free of oxygen or to
describe a microorganism which can grow in the absence of oxygen.
- anaerobic respiration
- Respiration under anaerobic conditions. The terminal electron acceptor, instead of oxygen in
the case of regular respira tion, can be: CO2 , Fe2+, fumarate, nitrate, nitrite, nitrous oxide,
sulphur, su lphate, etc. Note that anaerobic respiration still uses electron trasnport chain to
dump the electron whil e ferementation does not.
- without forming gas, e.g., anaerogenic 4fermentation.
- The C3a and C5a fractions during complement fixation. They act to mim ic some of the
reactions of anaphylaxis and ca n induce the release of histamine from mast cells. C5a is also
chemotacti c for neutrophils and monocytes.
- anaphylaxis (anaphylactic shock; type I reaction)
- A strong allergic reaction caused by an antigen-antibody reaction (immediate
- The process of formation of double-stranded DNA from single-stranded DNA; compare
- anoxic (noun: anoxia)
- Lack of oxygen. An adjective usually used to desribe a microbial habitat.
- anoxygenic photosynthesis
- A type of photosynthesis in green and purple bacteria in which oxygen is not produced. Use
of light energy to synthesize ATP by cyclic photo phosphorylation without oxygen production
in green and purple bacteri a.
- A chemical compound produced by one microorganism (especially fungi) which can inhibit
the growth of (or kill) other microorganisms. Antibiotics are used to treat infectious diseases.
Examples of some commonly used antibiotics are: penicillin, streptomycin, and tetracycline.
Inadequate use of antibiotics can lead to the developement of the resistance of the pathogens.
- A protein present in serum or other body fl uid that combines specifically with antigen. An
- A sequence of three bases in tRNA that base pairs with a codon in mRNA.
- A substance, usually macromolecular , that induces a specific immune response.
- antigen-presenting cell (APC)
- Cells that process and present antigen to T lymphocytes.
- antigenic determinants
- The portion of an antigen that interacts with an immunoglobulin or T cell receptor.
- antigenic drift
- In influenza virus, minor changes in viral proteins (antigens) due to gene mutation.
- An analogue of the end-product of a metabolic pathway that causes feedback inhibition or
repression, but cannot replace the genuine product; used for selecting feedback-deficient
- harmful to microorganisms by either killing or inhibiting growth.
- In reference to double-stranded DNA, the orie ntation of the two strnads: one strand runs
5'-->3', the other 3'-->5'
- antisense RNA
- An sequence of RNA which is complementary to the mRNA. Anitsense RNA can usually
interfere with translation process.
- An agent that kills or inhibits microbial growth but is not harmful t o human tissue.
- A serum containing anti bodies.
- A protein that allows RN polymerase to read through a terminator.
- An antibody that specifically interacts with and neutralizes a toxin
- An evolutionarily distinct group (domain) of prokayrotes consisting of the methanogens, most
extreme halophiles and hyperthermophiles, and Thermoplasma.
- An older term for the Archaea.
- aseptic technique
- Manipulation of sterile instruments or cu lture media in such a way as to maintain sterility.
- atomic weight
- The average weight of an atom of an element, i.e. the total mass of p rotons and neutrons in
- adenosine triphosphate (ATP)
- The principal energy carrier of the cell.
- 1. Reduction in the virulence of a pathogen; usually an attenuated pathogen is still cap able of
2. A process that plays a role in the regulation of enzymes involved in amino acid
- Antibodies that react to self antigens.
- autogenous control
- The expression of a gene is regulated by its own gene product(s).
- Immune reactions of a host against its own self constituents.
- Spontaneous lysis.
- Detection of radioactivity in a sample, for example a cell or gel, by placing it in contact with a
photographic film (e.g. X-ray film).
- In reference to carbon source - an organism which uses carbon dioxide (CO2) as the sole
carbon source. Compare with lithotroph, heterotroph, organotroph, and phototro ph.
- A mutant that has a growth factor requirement. Contrast with a prototroph.
Compiled by Tsute Chen, Converted by Ben Hoyt