| salmonellosis (sal²mo-nel-o_sis) | An infection with certain species of the genus Salmonella, usually caused by ingestion of food containing salmonellae or their products. Also known as Salmonella gastroenteritis or Salmonella food poisoning.
(See 931)
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| sanitization (san²ùõ-ti-za_shun) | Reduction of the microbial population on an inanimate object to levels judged safe by public health standards; usually, the object is cleaned.
(See 138)
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| saprophyte (sap_ro-fit) | An organism that takes up nonliving organic nutrients in dissolved form and usually grows on decomposing organic matter.
(See 557)
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| saprozoic nutrition (sap²ro-zo_ik) | Having the type of nutrition in which organic nutrients are taken up in dissolved form; normally refers to animals or animal-like organisms.
(See 586)
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| satellite phenomenon | See syntrophism.
(See 604)
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| scaffolding proteins | Special proteins that are used to aid procapsid construction during the assembly of a bacteriophage capsid and are removed after the completion of the procapsid.
(See 388)
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| scale (skøal) | A platelike organic structure found on the surface of some cells (chrysophytes).
(See 577)
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| scanning electron microscope (SEM) | An electron microscope that scans a beam of electrons over the surface of a specimen and forms an image of the surface from the electrons that are emitted by it.
(See 34)
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| scanning probe microscope | A microscope used to study surface features by moving a sharp probe over the object's surface (e.g., the scanning tunneling microscope).
(See 38)
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| scanning tunneling microscope | A type of scanning probe microscope used to image a surface by moving a fine probe over it at a constant height, which is maintained by keeping a constant electron flow (tunneling current) between the tip and surface.
(See 38)
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| scarlatina (skahr²la-te_nah) | See scarlet fever.
(See 905)
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| scarlet fever (scarlatina; skar_let) | A disease that results from infection with a strain of Streptococcus pyogenes that carries a lysogenic phage with the gene for erythrogenic (rash-inducing) toxin. The toxin causes shedding of the skin. This is a communicable disease spread by respiratory droplets.
(See 905)
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| schizogony (skùõ-zog_o-ne) | Multiple asexual fission.
(See 591)
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| secondary metabolites | Products of metabolism that are synthesized after growth has been completed.
(See 1002)
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| secondary treatment | The biological degradation of dissolved organic matter in the process of sewage treatment; the organic material is either mineralized or changed to settleable solids.
(See 659)
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| second law of thermodynamics | Physical and chemical processes proceed in such a way that the entropy of the universe (the system and its surroundings) increases to the maximum possible.
(See 156)
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| secretory IgA (sIgA) | The primary immunoglobulin of the secretory immune system. See IgA.
(See 738)
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| secretory vacuole | In protists and some animals, these organelles usually contain specific enzymes that perform various functions such as excystation. Their contents are released to the cell exterior during exocytosis.
(See 585)
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| segmented genome | A virus genome that is divided into several parts or fragments, each probably coding for the synthesis of a single polypeptide; segmented genomes are very common among the RNA viruses.
(See 374)
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| selectins (s@-lek_tins) | A family of cell adhesion molecules that are displayed on activated endothelial cells; examples include P-selectin and E-selectin. Selectins mediate leukocyte binding to the vascular endothelium.
(See 712)
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| selective media | Culture media that favor the growth of specific microorganisms; this may be accomplished by inhibiting the growth of undesired microorganisms.
(See 105)
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| selective toxicity | The ability of a chemotherapeutic agent to kill or inhibit a microbial pathogen while damaging the host as little as possible.
(See 807)
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| self-assembly | The spontaneous formation of a complex structure from its component molecules without the aid of special enzymes or factors.
(See 65, 207)
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| sepsis (sep_sis) | Systemic response to infection. This systemic response is manifested by two or more of the following conditions as a result of infection: temperature .38 or ,36°C; heart rate .90 beats per min; respiratory rate .20 breaths per min, or pCO2 ,32 mm Hg; leukocyte count .12,000 cells per ml3 or .10% immature (band) forms. Sepsis also has been defined as the presence of pathogens or their toxins in blood and other tissues.
(See 933)
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| septate (sep_tøat) | Divided by a septum or cross wall; also with more or less regular occurring cross walls.
(See 556)
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| septic shock (sep_tik) | Sepsis associated with severe hypotension despite adequate fluid resuscitation, along with the presence of perfusion abnormalities that may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status. Gram-positive bacteria, fungi, and endotoxin-containing gram-negative bacteria can initiate the pathogenic cascade of sepsis leading to septic shock.
(See 933)
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| septicemia (sep²tùõ-se_me-ah) | A disease associated with the presence in the blood of pathogens or bacterial toxins.
(See 514, 793)
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| septic tank (sep_tik) | A tank used to process small quantities of domestic sewage. Solid material settles out and is partially degraded by anaerobic bacteria as sewage slowly flows through the tank. The outflow is further treated or dispersed in aerobic soil.
(See 663)
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| septum (sep_tum; pl., septa) | A partition or cross-wall that occurs between two cells in a bacterial (e.g., actinomycete) or fungal filament, or which partitions off fungal structures such as spores. Septa also divide parent cells into two daughter cells during bacterial binary fission.
(See 286, 556)
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| serology (se-rol_o-je) | The branch of immunology that is concerned with in vitro reactions involving one or more serum constituents (e.g., antibodies and complement).
(See 774)
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| serotyping | A technique or serological procedure that is used to differentiate between strains (serovars or serotypes) of microorganisms that have differences in the antigenic composition of a structure or product.
(See 784)
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| serum (se_rum; pl., serums or sera) | The clear, fluid portion of blood lacking both blood cells and fibrinogen. It is the fluid remaining after coagulation of plasma, the noncellular liquid faction of blood.
(See 742)
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| serum resistance | The type of resistance that occurs with bacteria such as Neisseria gonorrhoeae because the pathogen interferes with membrane attack complex formation during the complement cascade.
(See 801)
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| settling basin | A basin used during water purification to chemically precipitate out fine particles, microorganisms, and organic material by coagulation or flocculation.
(See 652)
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| sex pilus (pi_lus) | A thin protein appendage required for bacterial mating or conjugation. The cell with sex pili donates DNA to recipient cells.
(See 63, 303)
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| sheath (shøeth) | A hollow tubelike structure surrounding a chain of cells and present in several genera of bacteria.
(See 496)
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| shigellosis (shùõ_g@l-o_sis) | The diarrheal disease that arises from an infection with a member of the genus Shigella. Often called bacillary dysentery.
(See 931)
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| SHIME system (simulated human intestinal microbial ecosystem) | A set of connected chemostat-like reactors that provide a sequence of environments similar to the human digestive system.
(See 987)
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| Shine-Dalgarno sequence | A segment in the leader of procaryotic mRNA that binds to a special sequence on the 16S rRNA of the small ribosomal subunit. This helps properly orient the mRNA on the ribosome.
(See 244)
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| shingles (zoster; shing_g_lz) | A reactivated form of chickenpox caused by the varicella-zoster virus.
(See 872)
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| siderophore (sid_er-o-for²) | A small molecule that complexes with ferric iron and supplies it to a cell by aiding in its transport across the plasma membrane.
(See 104)
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| sigma factor | A protein that helps the RNA polymerase core enzyme recognize the promoter at the start of a gene.
(See 262)
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| sign | An objective change in a diseased body that can be directly observed (e.g., a fever or rash).
(See 850)
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| silage | Fermented plant material with increased palatability and nutritional value for animals, which can be stored for extended periods.
(See 986)
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| silent mutation | A mutation that does not result in a change in the organism's proteins or phenotype even though the DNA base sequence has been changed.
(See 249)
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| simple matching coefficient (SSM) | An association coefficient used in numerical taxonomy; the proportion of characters that match regardless of whether or not the attribute is present.
(See 426)
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| single radial immunodiffusion (RID) assay | An immunodiffusion technique that quantitates antigens by following their diffusion through a gel containing antibodies directed against the test antigens.
(See 779)
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| site-specific recombination | Recombination of nonhomologous genetic material with a chromosome at a specific site.
(See 292)
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| skin-associated lymphoid tissue (SALT) | The lymphoid tissue in the skin that forms a first-line defense as a part of nonspecific immunity.
(See 709)
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| slash-and-burn agriculture | The cutting down and burning of tropical vegetation to make mineral nutrients available for use by introduced agricultural crops.
(See 672)
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| S-layer | A regularly structured layer composed of protein or glycoprotein that lies on the surface of many bacteria. It may protect the bacterium and help give it shape and rigidity.
(See 62)
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| slime | The viscous extracellular glycoproteins or glycolipids produced by staphylococci and Pseudomonas aeruginosa bacteria that allows them to adhere to smooth surfaces such as prosthetic medical devices and catheters. More generally, the term often refers to an easily removed, diffuse, unorganized layer of extracellular material that surrounds a bacterial cell.
(See 61, 919)
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| slime layer | A layer of diffuse, unorganized, easily removed material lying outside the bacterial cell wall.
(See 61)
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| slime mold | A common term for members of the divisions Acrasiomycota and Myxomycota.
(See 564)
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| slow sand filter | A bed of sand through which water slowly flows; the gelatinous microbial layer on the sand grain surface removes waterborne microorganisms, particularly Giardia, by adhesion to the gel. This type of filter is used in some water purification plants.
(See 653)
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| slow virus disease | A progressive, pathological process caused by a transmissible agent (virus or prion) that remains clinically silent during a prolonged incubation period of months to years after which progressive clinical disease becomes apparent.
(See 410, 893)
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| sludge (sluj) | A general term for the precipitated solid matter produced during water and sewage treatment; solid particles composed of organic matter and microorganisms that are involved in aerobic sewage treatment (activated sludge).
(See 658)
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| smallpox (variola; smawl_poks) | Once a highly contagious, often fatal disease caused by a poxvirus. Its most noticeable symptom was the appearance of blisters and pustules on the skin. Vaccination has eradicated smallpox throughout the world.
(See 876)
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| snapping division | A distinctive type of binary fission resulting in an angular or a palisade arrangement of cells, which is characteristic of the genera Arthrobacter and Corynebacterium.
(See 542)
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| sorocarp | The fruiting structure of the Acrasiomycetes.
(See 565)
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| sorus | A type of fruiting structure composed of a mass of spores or sporangia.
(See 565)
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| SOS repair | A complex, inducible repair process that is used to repair DNA when extensive damage has occurred.
(See 255)
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| source | The location or object from which a pathogen is immediately transmitted to the host, either directly or through an intermediate agent.
(See 854)
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| Southern blotting technique | The procedure used to isolate and identify DNA fragments from a complex mixture. The isolated, denatured fragments are transferred from an agarose electrophoretic gel to a nitrocellulose filter and identified by hybridization with probes.
(See 322)
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| specialized transduction | See restricted transduction.
(See 309)
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| species (spe_shøez) | Species of higher organisms are groups of interbreeding or potentially interbreeding natural populations that are reproductively isolated. Bacterial species are collections of strains that have many stable properties in common and differ significantly from other groups of strains.
(See 425)
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| specific immune response (acquired or specific immunity) | See acquired immunity.
(See 705)
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| spermosphere | The region surrounding a germinating seed where released organic matter stimulates microbial growth.
(See 974)
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| spheroplast (sføer_o-plast) | A relatively spherical cell formed by the weakening or partial removal of the rigid cell wall component (e.g., by penicillin treatment of gram-negative bacteria). Spheroplasts are usually osmotically sensitive.
(See 61)
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| spike | See peplomer.
(See 374)
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| spirillum (spi-ril_um) | A rigid, spiral-shaped bacterium.
(See 44)
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| spirochete (spi_ro-køet) | A flexible, spiral-shaped bacterium with periplasmic flagella.
(See 44, 479)
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| spleen (spløen) | A secondary lymphoid organ where old erythrocytes are destroyed and blood-borne antigens are trapped and presented to lymphocytes.
(See 708)
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| split or interrupted gene | A structural gene with DNA sequences that code for the final RNA product (expressed sequences or exons) separated by regions coding for RNA absent from the mature RNA (intervening sequences or introns).
(See 263)
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| spongiform encephalopathies | Degenerative central nervous system diseases in which the brain has a spongy appearance; they appear due to prions.
(See 893)
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| spontaneous generation (spon-ta_ne-us) | The hypothesis that living organisms can arise from nonliving matter.
(See 2)
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| sporadic disease (spo-rad_ik) | A disease that occurs occasionally and at random intervals in a population.
(See 849)
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| sporangiospore (spo-ran_je-o-spøor) | A spore born within a sporangium.
(See 539, 557)
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| sporangium (spo-ran_je-um; pl., sporangia) | A saclike structure or cell, the contents of which are converted into an indefinite number of spores. It is borne on a special hypha called a sporangiophore.
(See 68, 557)
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| spore (spøor) | A differentiated, specialized form that can be used for dissemination, for survival of adverse conditions because of its heat and dessication resistance, and/or for reproduction. Spores are usually unicellular and may develop into vegetative organisms or gametes. They may be produced asexually or sexually and are of many types.
(See 573)
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| sporogenesis (spor_o-jen_ùe-sis) | See sporulation.
(See 69)
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| sporotrichosis (spo²ro-tri-ko_sis) | A subcutaneous fungal infection caused by the dimorphic fungus Sporothrix schenckii.
(See 945)
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| sporulation (spor²u-la_shun) | The process of spore formation.
(See 69)
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| spread plate | A petri dish of solid culture medium with isolated microbial colonies growing on its surface, which has been prepared by spreading a dilute microbial suspension evenly over the agar surface.
(See 106)
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| sputum (spu_tum) | The mucous secretion from the lungs, bronchi, and trachea that is ejected (expectorated) through the mouth.
(See 829)
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| stalk (stawk) | A nonliving bacterial appendage produced by the cell and extending from it.
(See 490)
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| standard free energy change | The free energy change of a reaction at 1 atmosphere pressure when all reactants and products are present in their standard states; usually the temperature is 25°C.
(See 156)
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| standard reduction potential | A measure of the tendency of a reductant to lose electrons in an oxidation-reduction (redox) reaction. The more negative the reduction potential of a compound, the better electron donor it is.
(See 157)
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| staphylococcal food poisoning (staf²i-lo-kok_al) | A type of food poisoning caused by ingestion of improperly stored or cooked food in which Staphylococcus aureus has grown. The bacteria produce exotoxins that accumulate in the food.
(See 932)
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| staphylococcal scalded skin syndrome (SSSS) | A disease caused by staphylococci that produce an exfoliative toxin. The skin becomes red (erythema) and sheets of epidermis may separate from the underlying tissue.
(See 922)
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| starter culture | An inoculum, consisting of a mixture of carefully selected microorganisms, used to start a commercial fermentation.
(See 978)
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| stationary phase (sta_shun-er²e) The phase | of microbial growth in a batch culture when population growth ceases and the growth curve levels off.
(See 114)
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| statistics (stah-tis_tiks) | The mathematics of the collection, organization, and interpretation of numerical data.
(See 849)
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| stem-nodulating rhizobia | Rhizobia (members of the genera Rhizobium, Bradyrhizobium, and Azorhizobium) that produce nitrogen-fixing structures above the soil surface on plant stems. These most often are observed in tropical plants and produced by Azorhizobium.
(See 682)
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| sterilization (ster²ùõ-lùõ-za_shun) | The process by which all living cells, viable spores, viruses, and viroids are either destroyed or removed from an object or habitat.
(See 137)
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| stigma (stig_mah) | A light-sensitive eyespot, which is found in some algae and photosynthetic protozoa; it is believed to be involved in phototaxis, at least in some cases.
(See 575)
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| stoneworts | A group of approximately 250 species of algae that have a complex growth pattern, with nodal regions from which whorls of branches arise; they are abundant in fresh to brackish waters.
(See 576)
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| strain | A population of organisms that descends from a single organism or pure culture isolate.
(See 425)
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| streak plate | A petri dish of solid culture medium with isolated microbial colonies growing on its surface, which has been prepared by spreading a microbial mixture over the agar surface, using an inoculating loop.
(See 107)
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| streptococcal pneumonia | An endogenous infection of the lungs caused by Streptococcus pneumoniae that occurs in predisposed individuals.
(See 905)
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| streptococcal sore throat (strep²to-kok_al) | One of the most common bacterial infections of humans. It is commonly referred to as "strep throat." The disease is spread by droplets of saliva or nasal secretions and is caused by Streptococcus spp. (particularly group A streptococci).
(See 905)
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| streptolysin-O (SLO) (strep-tol_ùõ-sin) | A specific hemolysin produced by Streptococcus pyogenes that is inactivated by oxygen (hence the "O" in its name). SLO causes beta-hemolysis of blood cells on agar plates incubated anaerobically.
(See 797)
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| streptolysin-S (SLS) | A product produced by Streptococcus pyogenes that is bound to the bacterial cell but may sometimes be released. SLS causes beta hemolysis on aerobically incubated blood-agar plates and can act as a leukocidin by killing leukocytes that phagocytose the bacterial cell to which it is bound.
(See 797)
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| streptomycin (strep_to-mi²sin) | A bactericidal aminoglycoside antibiotic produced by Streptomyces griseus.
(See 816)
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| strict anaerobes | See obligate anaerobes.
(See 127)
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| stroma (stro_mah) | The chloroplast matrix that is the location of the photosynthetic carbon dioxide fixation reactions.
(See 85)
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| stromatolite (stro²mah-to_løõt) | Dome-like microbial mat communities consisting of filamentous photosynthetic bacteria and occluded sediments (often calcareous or siliceous). They usually have a laminar structure. Many are fossilized, but some modern forms occur.
(See 423)
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| structural gene | A gene that codes for the synthesis of a polypeptide or polynucleotide with a nonregulatory function.
(See 277)
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| subacute sclerosing panencephalitis | Diffuse inflammation of the brain resulting from virus and prion infections.
(See 874)
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| subgingival plaque (sub-jin_jùõ-val) | The plaque that forms at the dentogingival margin and extends down into the gingival tissue.
(See 936)
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| substrate-level phosphorylation | The synthesis of ATP from ADP by phosphorylation coupled with the exergonic breakdown of a high-energy organic substrate molecule.
(See 177)
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| subsurface biosphere | The region below the plant root zone where microbial populations can grow and function.
(See 691)
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| sulfate reduction (sul_føat) | The process of sulfate use as an oxidizing agent, which results in the accumulation of reduced forms of sulfur such as sulfide, or incorporation of sulfur into organic molecules, usually as sulfhydryl groups.
(See 614)
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| sulfonamide (sul-fon_ah-møõd) | A chemotherapeutic agent that has the SO2-NH2 group and is a derivative of sulfanilamide.
(See 812)
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| superantigen | Superantigens are bacterial proteins that stimulate the immune system much more extensively than do normal antigens. They stimulate T cells to proliferate nonspecifically through simultaneous interaction with class II MHC proteins on antigen-presenting cells and variable regions on the b chain of the T-cell receptor complex. Examples include streptococcal scarlet fever toxins, staphylococcal toxic shock syndrome toxin-1, and streptococcal M protein.
(See 732)
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| superinfection (soo²per-in-fek_shun) | A new bacterial or fungal infection of a patient that is resistant to the drug(s) being used for treatment.
(See 819)
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| superoxide dismutase (SOD; soo²per-ok_søõd dis-mu_tas) | An enzyme that protects many microorganisms by catalyzing the destruction of the toxic superoxide radical.
(See 128)
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| suppressor mutation | A mutation that overcomes the effect of another mutation and produces the normal phenotype.
(See 248)
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| Svedberg unit (sfed_berg) | The unit used in expressing the sedimentation coefficient; the greater a particle's Svedberg value, the faster it travels in a centrifuge.
(See 52)
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| swab (swahb) | A wad of absorbent material usually wound around one end of a small stick and used for applying medication or for removing material from an area; also, a dacron-tipped polystyrene applicator.
(See 827)
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| swarm cell | A flagellated cell; the term is usually applied to the motile cells of the Myxomycota.
(See 565)
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| symbiosis (sim_bi-o_sis) | The living together or close association of two dissimilar organisms, each of these organisms being known as a symbiont.
(See 596)
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| symbiosome | The final nitrogen-fixing form of Rhizobium that is active within root nodule cells.
(See 676)
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| symptom (simp_t@m) | A change during a disease that a person subjectively experiences (e.g., pain, bodily discomfort, fatigue, or loss of appetite). Sometimes the term symptom is used more broadly to include any observed signs.
(See 850)
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| syndrome | See disease syndrome.
(See 850)
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| synthetic medium | See defined medium.
(See 105)
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| syntrophism (sin_trøof-iz@m) | The association in which the growth of one organism either depends on, or is improved by, the provision of one or more growth factors or nutrients by a neighboring organism. Sometimes both organisms benefit. This type of mutualism is also known as cross-feeding or the satellite phenomenon.
(See 604)
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| syphilis (sif_ùõ-lis) | See venereal syphilis.
(See 923)
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| systematic epidemiology | The field of epidemiology that focuses on the ecological and social factors that influence the development of emerging and reemerging infectious diseases.
(See 859)
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| systematics (sis_te-mat_iks) | The scientific study of organisms with the ultimate objective being to characterize and arrange them in an orderly manner; often considered synonymous with taxonomy.
(See 422)
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| systemic lupus erythematosus (loo_pus er_ùõ-them-ah-to_sus) | An autoimmune, inflammatory disease that may affect every tissue of the body.
(See 770)
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| taxon (tak_son) | A group into which related organisms are classified.
(See 422)
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| taxonomy (tak-son_o-me) | The science of biological classification; it consists of three parts: classification, nomenclature, and identification.
(See 422)
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| TB skin test | Tuberculin hypersensitivity test for a previous or current infection with Mycobacterium tuberculosis.
(See 771)
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| T cell or T lymphocyte | A type of lymphocyte derived from bone marrow stem cells that matures into an immunologically competent cell under the influence of the thymus. T cells are involved in a variety of cell-mediated immune reactions.
(See 705, 745)
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| T-cell antigen receptor (TCR) | The receptor on the T cell surface consisting of two antigen-binding peptide chains; it is associated with a large number of other glycoproteins. Binding of antigen to the TCR, usually in association with MHC, activates the T cell.
(See 745)
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| T-dependent antigen | An antigen that effectively stimulates B-cell response only with the aid of T-helper cells that produce interleukin-2 and B-cell growth factor.
(See 753)
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| teichoic acids (ti-ko_ik) | Polymers of glycerol or ribitol joined by phosphates; they are found in the cell walls of gram-positive bacteria.
(See 56)
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| temperate phages | Bacteriophages that can infect bacteria and establish a lysogenic relationship rather than immediately lysing their hosts.
(See 308, 390)
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| template strand (tem_plat) | A strand of DNA or RNA that specifies the base sequence of a newly synthesized complementary strand of DNA or RNA.
(See 242)
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| terminator | A sequence that marks the end of a gene and stops transcription.
(See 244, 263)
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| tertiary treatment (ter_she-er-e) | The removal from sewage of inorganic nutrients, heavy metals, viruses, etc., by chemical and biological means after microorganisms have degraded dissolved organic material during secondary sewage treatment.
(See 661)
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| test | A loose-fitting shell of an amoeba.
(See 590)
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| tetanolysin (tet_ah-nol_ùõ-sin) | A hemolysin that aids in tissue destruction and is produced by Clostridium tetani.
(See 925)
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| tetanospasmin (tet_ah-no-spaz_min) | The neurotoxic component of the tetanus toxin, which causes the muscle spasms of tetanus. Tetanospasmin production is under the control of a plasmid gene.
(See 924)
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| tetanus (tet_ah-nus) | An often fatal disease caused by the anaerobic, spore-forming bacillus Clostridium tetani, and characterized by muscle spasms and convulsions.
(See 924)
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| tetracyclines (tet_rah-si_kløens) | A family of antibiotics with a common four-ring structure, which are isolated from the genus Streptomyces or produced semisynthetically; all are related to chlortetracycline or oxytetracycline.
(See 815)
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| tetrapartite associations (tet_rah-par_tøõt) | A mutualistic association of the same plant with three different types of microorganisms.
(See 685)
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| TH1 cell | See regulator T cell.
(See 751)
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| TH2 cell | See regulator T cell.
(See 751)
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| TH0 cell | See regulator T cell.
(See 751)
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| thallus (thal_us) | A type of body that is devoid of root, stem, or leaf; characteristic of some algae, many fungi, and lichens.
(See 537, 554, 573)
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| T-helper (TH) cell | A cell that is needed for T-cell-dependent antigens to be effectively presented to B cells. It also promotes cell-mediated immune responses.
(See 751)
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| theory | A set of principles and concepts that have survived rigorous testing and that provide a systematic account of some aspect of nature.
(See 8)
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| thermal death time (TDT) | The shortest period of time needed to kill all the organisms in a microbial population at a specified temperature and under defined conditions.
(See 140)
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| thymus (thi_m@s) | A primary lymphoid organ in the chest that is necessary in early life for the development of immunological functions. T-cell maturation takes place here.
(See 708)
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| thermoacidophiles | A group of bacteria that grow best at acid pHs and high temperatures; they are members of the Archaea.
(See 457)
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| thermophile (ther_mo-føõl) | A microorganism that can grow at temperatures of 55°C or higher; the minimum is usually around 45°C.
(See 126)
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| thrush (thrush) | Infection of the oral mucous membrane by the fungus Candida albicans; also known as oral candidiasis.
(See 949)
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| thylakoid (thi_lah-koid) | A flattened sac in the chloroplast stroma that contains photosynthetic pigments and the photosynthetic electron transport chain; light energy is trapped and used to form ATP and NAD(P)H in the thylakoid membrane.
(See 85)
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| thymine (thi_min) | The pyrimidine 5-methyluracil that is found in nucleosides, nucleotides, and DNA.
(See 217)
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| T-independent antigen | An antigen that triggers a B cell into immunoglobulin production without T-cell cooperation.
(See 754)
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| Ti or Ri plasmid | A plasmid obtained from Agrobacterium tumefaciens that is used to insert genes into plant cells.
(See 339, 684)
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| tinea (tin_e-ah) | A name applied to many different kinds of superficial fungal infections of the skin, nails, and hair, the specific type (depending on characteristic appearance, etiologic agent, and site) usually designated by a modifying term.
(See 943)
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| tinea capitis | A fungal infection of scalp hair caused by species of Trichophyton or Microsporum.
(See 943)
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| tinea corporis | A fungal infection of the smooth parts of the skin caused by either Trichophyton rubrum, T. mentagrophytes, or Microsporum canis.
(See 943)
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| tinea cruris | A fungal infection of the groin caused by either Epidermophyton floccosum, Trichophyton mentagrophytes, or T. rubrum; also known as jock itch.
(See 944)
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| tinea manuum | A fungal infection of the hand caused by Trichophyton rubrum, T. mentagrophytes, or E. floccosum.
(See 944)
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| tinea pedis | A fungal infection of the foot caused by Trichophyton rubrum, T. mentagrophytes, or E. floccosum; also known as athlete's foot.
(See 944)
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| tinea unguium | A fungal infection of the nail bed caused by either Trichophyton rubrum or T. mentagrophytes.
(See 944)
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| tinea versicolor | A fungal infection caused by the yeast, Malassezia furfur, that forms brownish-red scales on the skin of the trunk, neck, face, and arms.
(See 943)
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| titer (ti_ter) | Reciprocal of the highest dilution of an antiserum that gives a positive reaction in the test being used.
(See 742)
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| T lymphocyte | See T cell.
(See 705)
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| tonsillitis (ton_si-li_tis) | Inflammation of the tonsils, especially the palatine tonsils often due to S. pyogenes infection.
(See 905)
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| toxemia (tok-se_me-ah) | The condition caused by toxins in the blood of the host.
(See 794)
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| toxic shock-like syndrome (TSLS) | A disease caused by an invasive group A streptococcus infection that is characterized by a rapid drop in blood pressure, failure of many organs, and a very high fever. It probably results from the release of one or more streptococcal pyrogenic exotoxins.
(See 904)
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| toxic shock syndrome (tok_sik) | A staphylococcal disease that most commonly affects females who use certain types of tampons during menstruation. It is associated with the production of toxic shock syndrome toxin by certain strains of Staphylococcus aureus.
(See 922)
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| toxigenicity (tok_sùõ-jùe-nis_i-tøe) | The capacity of an organism to produce a toxin.
(See 790)
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| toxin (tok_sin) | A microbial product or component that can injure another cell or organism at low concentrations. Often the term refers to a poisonous protein, but toxins may be lipids and other substances.
(See 794)
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| toxin neutralization | The inactivation of toxins by specific antibodies, called antitoxins, that react with them.
(See 756)
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| toxoid (tok_soid) | A bacterial exotoxin that has been modified so that it is no longer toxic but will still stimulate antitoxin formation when injected into a person or animal.
(See 767, 796)
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| toxoplasmosis (tok_so-plaz-mo_sis) | A disease of animals and humans caused by the parasitic protozoan, Toxoplasma gondii.
(See 957)
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| trachoma (trah-ko_mah) | A chronic infectious disease of the conjunctiva and cornea, producing pain, inflammation and sometimes blindness. It is caused by Chlamydia trachomatis serotypes A-C.
(See 925)
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| transamination (trans_am-i-na_shun) | The removal of amino acid's amino group by transferring it to an a-keto acid acceptor.
(See 192)
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| transcriptase (trans-krip_tøas) | An enzyme that catalyzes transcription; in viruses with RNA genomes, this enzyme is an RNA-dependent RNA polymerase that is used to make RNA copies of the RNA genomes.
(See 406)
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| transcription (trans-krip_shun) | The process in which single-stranded RNA with a base sequence complementary to the template strand of DNA or RNA is synthesized.
(See 230)
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| transduction (trans-duk_shun) | The transfer of genes between bacteria by bacteriophages.
(See 308)
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| transfer host (trans_fer) | A host that is not necessary for the completion of a parasite's life cycle, but is used as a vehicle for reaching a final host.
(See 789)
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| transfer RNA (tRNA) | A small RNA that binds an amino acid and delivers it to the ribosome for incorporation into a polypeptide chain during protein synthesis.
(See 261)
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| transformation (trans_for-ma_shun) | A mode of gene transfer in bacteria in which a piece of free DNA is taken up by a bacterial cell and integrated into the recipient genome.
(See 228, 305)
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| transgenic animal or plant | An animal or plant that has gained new genetic information from the insertion of foreign DNA. It may be produced by such techniques as injecting DNA into animal eggs, electroporation of mammalian cells and plant cell protoplasts, or shooting DNA into plant cells with a gene gun.
(See 335)
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| transient carrier | See casual carrier.
(See 854)
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| transition mutations (tran-zish_un) | Mutations that involve the substitution of a different purine base for the purine present at the site of the mutation or the substitution of a different pyrimidine for the normal pyrimidine.
(See 246)
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| translation (trans-la_shun) | Protein synthesis; the process by which the genetic message carried by mRNA directs the synthesis of polypeptides with the aid of ribosomes and other cell constituents.
(See 230)
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| transmission electron microscope (trans-mish_un) | A microscope in which an image is formed by passing an electron beam through a specimen and focusing the scattered electrons with magnetic lenses.
(See 30)
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