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D

  • dacryocystitis inflammation of the lacrimal sac often associated with a plugged nasolacrimal duct
  • daptomycin cyclic lipopetide that disrupts the bacterial cell membrane
  • darkfield microscope a compound light microscope that produces a bright image on a dark background; typically a modified brightfield microscope
  • death phase (decline phase) phase of the growth curve at which the number of dying cells exceeds the number of new cells formed
  • decimal reduction time (DRT) or D-value amount of time it takes for a specific protocol to produce a one order of magnitude decrease in the number of organisms; that is, death of 90% of the population
  • decolorizing agent a substance that removes a stain, usually from some parts of the specimen
  • deeply branching bacteria bacteria that occupy the lowest branches of the phylogenetic tree of life
  • definitive host the preferred host organism for a parasite, in which the parasite reaches maturity and may reproduce sexually
  • degeneracy redundancy in the genetic code because a given amino acid is encoded by more than one nucleotide triplet codon
  • degerming protocol that significantly reduces microbial numbers by using mild chemicals (e.g., soap) and gentle scrubbing of a small area of skin or tissue to avoid the transmission of pathogenic microbes
  • degranulation release of the contents of mast cell granules in response to the cross-linking of IgE molecules on the cell surface with allergen molecules
  • dehydration synthesis chemical reaction in which monomer molecules bind end to end in a process that results in the formation of water molecules as a byproduct
  • deletion type of mutation involving the removal of one or more bases from a DNA sequence
  • Deltaproteobacteria class of Proteobacteria that includes sulfate-reducing bacteria
  • denatured protein protein that has lost its secondary and tertiary structures (and quaternary structure, if applicable) without the loss of its primary structure
  • dendrites branched extensions of the soma of a neuron that interact with other cells
  • dengue fever mosquito-borne viral hemorrhagic disease; also known as breakbone fever
  • dental calculus calcified heavy plaque on teeth, also called tartar
  • dental caries cavities formed in the teeth as a result of tooth decay caused by microbial activity
  • deoxyribonucleic acid (DNA) double-stranded nucleic acid composed of deoxyribonucleotides that serves as the genetic material of the cell
  • deoxyribonucleotides DNA nucleotides containing deoxyribose as the pentose sugar component
  • dermatophyte any fungus of the genera Microsporum, Epidermophyton, or Trichophyton , which feed on keratin (a protein found in skin, hair, and nails) and can cause cutaneous infections
  • dermis the second layer of human skin, found between the epidermis and the hypodermis
  • descriptive epidemiology a method of studying a disease outbreak using case histories, contact interviews, medical information, and other sources of information
  • desensitization injections of antigen that lead to production of antigen-specific IgG molecules, effectively outcompeting IgE molecules on the surface of sensitized mast cells for antigen
  • desiccation method of microbial control involving the removal of water from cells through drying or dehydration
  • desquamation peeling and shedding of outermost skin
  • diapedesis process by which leukocytes pass through capillary walls to reach infected tissue; also called extravasation
  • diaphragm a component of a microscope; typically consists of a disk under the stage with holes of various sizes; can be adjusted to allow more or less light from the light source to reach the specimen
  • differential interference-contrast microscope a microscope that uses polarized light to increase contrast
  • differential media media that contain additives that make it possible to distinguish bacterial colonies based on metabolic activities of the organisms
  • differential staining staining that uses multiple dyes to differentiate between structures or organisms
  • diffraction the changing of direction (bending or spreading) that occurs when a light wave interacts with an opening or barrier
  • dikaryotic having two separate nuclei within one cell
  • dimorphic fungus a fungus that can take the form of a yeast or a mold, depending on environmental conditions
  • dioecious refers to sexually reproducing organisms in which individuals have either male or female reproductive organs (not both)
  • diphtheria serious infection of the larynx, caused by the toxigenic bacterium Corynebacterium diphtheriae
  • diploid having two copies of each chromosome
  • direct agglutination assay assay that can be used to detect the agglutination of bacteria by the action of antibodies in patient serum
  • direct antihuman globulin test (DAT) another name for a direct Coombs’ test
  • direct contact transmission movement of a pathogen between hosts by physical contact or transfer in droplets at a distance less than one meter
  • direct Coombs’ test assay that looks for antibodies in vivo against red blood cells caused by various types of infections, drug reactions, and autoimmune disorders
  • direct ELISA enzyme-linked immunoabsorbent assay in which the antigens are immobilized in the well of a microtiter plate; only a single antibody is used in the test
  • direct fluorescent antibody (DFA) test FA technique in which the labeled antibody binds to the target antigen
  • direct hemagglutination assay test that determines the titer of certain bacteria and viruses that causes clumping of red blood cells
  • direct microscopic cell count counting of cells using a calibrated slide under a light microscope
  • direct repair (light repair or photoreactivation) light-dependent mechanism for repairing pyrimidine dimers involving the enzyme photolyase
  • disaccharide one of two monosaccharides linked together by a glycosidic bond
  • disease any condition in which the normal structure or function of the body is damaged or impaired
  • disinfectant antimicrobial chemical applied to a fomite during disinfection that may be toxic to tissues
  • disinfection protocol that removes potential pathogens from a fomite
  • disk-diffusion method a technique for measuring of the effectiveness of one or more antimicrobial agents against a known bacterium; involves measuring the zone(s) of inhibition around the chemical agent(s) in a culture of the bacterium
  • dispersion the separation of light of different frequencies due to different degrees of refraction
  • disulfide bridge covalent bond between the sulfur atoms of two sulfhydryl side chains
  • DNA gyrase (topoisomerase II) bacterial topoisomerase that relaxes the supercoiled chromosome to make DNA more accessible for the initiation of replication
  • DNA ligase enzyme that catalyzes the formation of a covalent phosphodiester linkage between the 3’-OH end of one DNA fragment and the 5’ phosphate end of another DNA fragment
  • DNA packaging process in which histones or other DNA binding proteins perform various levels of DNA wrapping and attachment to scaffolding proteins to allow the DNA to fit inside a cell
  • DNA polymerase class of enzymes that adds nucleotides to the free 3’-OH group of a growing DNA chain that are complementary to the template strand
  • DNA primers short, synthetic, single-stranded DNA fragments of known sequence that bind to specific target sequences within a sample due to complementarity between the target DNA sequence and the primer; commonly used in PCR but may be used in other hybridization techniques
  • DNA probe a single-stranded DNA fragment that is complementary to part of the gene (DNA or RNA) of interest
  • DNAse pathogen-produced nuclease that degrades extracellular DNA
  • dosage amount of medication given during a certain time interval
  • double immunodiffusion see Ouchterlony assay
  • doubling time the time it takes for the population to double; also referred to as generation time
  • droplet transmission direct contact transmission of a pathogen transferred in sneezed or coughed droplets of mucus that land on the new host within a radius of one meter
  • drug resistance ability of a microbe to persist and grow in the presence of an antimicrobial drug
  • dry-heat sterilization protocol that involves the direct application of high heat
  • dura mater tough, outermost membrane that surrounds the brain
  • dynein motor proteins that interact with microtubules in eukaryotic flagella and cilia
  • dysentery intestinal inflammation that causes diarrhea with blood and mucus
  • dysuria urination accompanied by burning, discomfort, or pain

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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