0.5 Glossary  (Page 14/18)

P

• P (peptidyl) site functional site of an intact ribosome that binds charged tRNAs carrying amino acids that have formed peptide bonds with the growing polypeptide chain but have not yet dissociated from their corresponding tRNA
• palatine tonsil lymphoid tissue located near the oropharynx
• pandemic disease an epidemic that is worldwide as opposed to regional
• papilloma growth on the skin associated with infection by any of the human papilloma viruses (HPV); commonly known as a wart
• paracrine function refers to a cytokine signal released from a cell to a receptor on a nearby cell
• parasitism type of symbiosis in which one population benefits while harming the other parasitology the study of parasites
• parenteral route means of entry by a pathogen through skin or mucous membranes when these barriers are breached
• paroxysmal stage most serious stage of pertussis (whooping cough), characterized by severe and prolonged coughing spells
• passive carrier an individual capable of transmitting a pathogen to another individual without becoming infected
• passive immunity adaptive immune defenses received from another individual or animal
• pasteurization form of microbial control using heat that is applied to foods; kills pathogens and reduces the number of spoilage-causing microbes while maintaining food quality
• pathogen a disease-causing microorganism
• pathogen-associated molecular patterns (PAMPs) common molecular motifs found on pathogens
• pathogenicity ability of a microbial agent to cause disease
• pattern recognition receptors (PRRs) receptors on the surface or in the interior of phagocytic cells that bind to pathogen-associated molecular patterns (PAMPs)
• pellicle structure that underlies the plasma membrane in protists, providing additional support
• pelvic inflammatory disease (PID) infection of the female reproductive organs that may spread from the vagina to the cervix, uterus, fallopian tubes, and ovaries
• penetration entry of phage or virus into a host cell through injection, endocytosis, or membrane fusion
• penicillin β-lactam antibacterial that was the first cell wall synthesis inhibitor developed
• penis external genital organ in males through which urine and semen are discharged
• pentamidine antiprotozoan drug that appears to degrade kDNA in target cells, as well as inhibit protein synthesis
• pentose phosphate pathway (PPP) alternative glycolytic pathway that produces intermediates used for the biosynthesis of nucleotides and amino acids; also called the phosphogluconate pathway or the hexose monophosphate shunt
• peptic ulcer an ulcer in the lining of the stomach or duodenum, often associated with Helicobacter pylori
• peptide bond bond between the carboxyl group of one amino acid and the amine group of another; formed with the loss of a water molecule
• peptidoglycan (murein) the polymer of alternating N-acetylmuramic acid NAM and N-acetylglucosamine (NAG) subunits linked together by peptide chains; a major constituent of bacterial cell walls
• peptidyl transferase RNA-based ribozyme that is part of the 50S ribosomal subunit and catalyzes formation of the peptide bond between the amino acid bound to a tRNA and the growing polypeptide chain
• perforin compound released from a natural killer cell that creates pores in the target cell through which other toxins (particularly granzymes) can gain access to the cytoplasm
• pericarditis inflammation of the sac that surrounds the heart
• period of convalescence fifth stage of acute disease, during which the patient returns to normal function
• period of decline fourth stage of disease, during which the number of pathogens present in the host decreases, along with signs and symptoms of disease
• period of illness third stage of acute disease, during which the number of pathogens present in the host is greatest and the signs and symptoms of disease are most severe
• periodontal disease a condition in which the gums are inflamed and may erode
• periodontitis inflammation of the gums that is more severe than gingivitis, spreading deeper into the tissues
• peripheral nervous system network of neurons that connects the CNS with organs, sensory organs, and muscles throughout the body
• peripheral tolerance mechanism by which regulatory T cells inhibit self-reactive immune responses in T cells that have already exited the thymus
• periplasmic space the space between the cell wall and the plasma membrane, primarily in gram-negative bacteria
• peristalsis muscular contractions of the gastrointestinal tract that propel ingested material through the stomach, intestines, and, eventually, through the rectum and out of the body
• peritrichous having numerous flagella covering the entire surface of a bacterial cell
• peroxidase enzyme that catalyzes the detoxification of peroxides
• peroxisome in eukaryotic cells, a membrane-bound organelle (not part of the endomembrane system) that produces hydrogen peroxide to break down various types of molecules; also plays a role in lipid biosynthesis
• peroxygen type of strong oxidizing agent that causes free radical formation in cells; can be used as a disinfectant or antiseptic
• persister dormant cell that survives in the death phase and is resistant to most antibiotics
• pertussis contagious illness caused by Bordetella pertussis that causes severe coughing fits followed by a whooping sound during inhalation; commonly known as whooping cough
• pertussis toxin main virulence factor accounting for the symptoms of whooping cough
• petechiae small red or purple spots on the skin that result from blood leaking out of damaged vessels
• Petroff-Hausser counting chamber calibrated slide that allows counting of bacteria in a specific volume under a microscope
• Peyer’s patches lymphoid tissue in the ileum that monitors and fights infections
• phagemid a plasmid capable of being replicated as a plasmid and also incorporated into a phage head
• phagocytosis a type of endocytosis in which large particles are engulfed by membrane invagination, after which the particles are enclosed in a pocket, which is pinched off from the membrane to form a vacuole
• phagolysosome compartment in a phagocytic cell that results when the phagosome is fused with the lysosome, leading to the destruction of the pathogens inside
• phagosome compartment in the cytoplasm of a phagocytic cell that contains the phagocytosed pathogen enclosed by part of the cell membrane
• pharmacogenomics (toxicogenomics) the evaluation of the effectiveness and safety of drugs on the basis of information from an individual’s genomic sequence as well as examination of changes in gene expression in response to the drug
• pharyngitis inflammation of the pharynx
• pharynx region connecting the nose and mouth to the larynx: the throat
• phase-contrast microscope a light microscope that uses an annular stop and annular plate to increase contrast
• phenol coefficient measure of the effectiveness of a chemical agent through comparison with that of phenol on Staphylococcus aureus and Salmonella enterica serovar Typhi
• phenolics class of chemical disinfectants and antiseptics characterized by a phenol group that denatures proteins and disrupts membranes
• phenotype observable characteristics of a cell or organism
• phosphodiester bonds linkage whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide
• phosphogluconate pathway see pentose phosphate pathway
• phospholipase enzyme that degrades phospholipids
• phospholipid complex lipid that contains a phosphate group
• phospholipid-derived fatty acids (PLFA) analysis technique in which membrane phospholipids are saponified to release the fatty acids of the phospholipids, which can be subjected to FAME analysis for identification purposes
• phosphorescence the ability of certain materials to absorb energy and then release that energy as light after a delay
• photosynthesis process whereby phototrophic organisms convert solar energy into chemical energy that can then be used to build carbohydrates
• photosynthetic pigment pigment molecule used by a cell to absorb solar energy; each one appears the color of light that it transmits or reflects
• photosystem organized unit of pigments found within a photosynthetic membrane, containing both a light-harvesting complex and a reaction center
• phototaxis directional movement using flagella in response to light
• phototroph organism that gets its energy from light
• phototrophic bacteria nontaxonomic group of bacteria that use sunlight as their primary source of energy
• phylogeny the evolutionary history of a group of organisms
• phytoplankton photosynthetic plankton
• pia mater fragile and innermost membrane layer surrounding the brain
• pili long protein extensions on the surface of some bacterial cells; specialized F or sex pilus aids in DNA transfer between cells
• pinocytosis a type of endocytosis in which small dissolved materials are endocytosed into smaller vesicles
• plague infectious epidemic disease caused by Yersinia pestis
• plankton microscopic organisms that float in the water and are carried by currents; they may be autotrophic (phytoplankton) or heterotrophic (zooplankton)
• planktonic free-floating or drifting in suspension
• plantibodies monoclonal antibodies produced in plants that are genetically engineered to express mouse or human antibodies
• plaque clear area on bacterial lawn caused by viral lysis of host cells
• plasma cell activated and differentiated B cell that produces and secretes antibodies
• plasma fluid portion of the blood that contains all clotting factors
• plasma membrane (also called the cell membrane or cytoplasmic membrane) lipid bilayer with embedded proteins that defines the boundary of the cell
• plasmalemma protist plasma membrane
• plasmid small, circular, double-stranded DNA molecule that is typically independent from the bacterial chromosome
• plasmolysis the separation of the plasma membrane away from the cell wall when a cell is exposed to a hypertonic environment
• platelets cell fragments in the peripheral blood that originate from megakaryocyte cells in the bone marrow; also called thrombocytes
• Platyhelminthes phylum comprising flatworms
• pleconaril an antiviral drug targeting picornaviruses that prevents the uncoating of virus particles upon their infection of host cells
• pleomorphic able to change shape
• pneumococcal meningitis bacterial infection caused by Streptococcus pneumoniae that results in an inflammation of the meninges
• Pneumocystis pneumonia common pulmonary infection in patients with AIDS; caused by P. jirovecii
• pneumonia pulmonary inflammation that causes the lungs to fill with fluids
• pneumonic plague rare form of plague that causes massive hemorrhages in the lungs and is communicable through aerosols
• point mutation mutation, most commonly a base substitution, that affects a single base pair
• point source spread a form of common source spread in which the transmission of a disease from the source occurs for a brief period that is less than the pathogen’s incubation period
• polar tubule a tube-like structure produced by spores of parasitic Microsporidia fungi that pierces host cell membranes
• poliomyelitis (polio) disease caused by an infection of the enteric polio virus characterized by inflammation of the motor neurons of the brain stem and spinal cord; can result in paralysis
• poly-A tail string of approximately 200 adenine nucleotides added to the 3’ end of a eukaryotic primary mRNA transcript to stabilize it
• polyacrylamide gel electrophoresis (PAGE) a method for separating populations of proteins and DNA fragments during Sanger sequencing of varying sizes by differential migration rates caused by a voltage gradient through a vertical gel matrix
• polycistronic mRNA single mRNA molecule commonly produced during prokaryotic transcription that carries information encoding multiple polypeptides
• polyclonal antibodies antibodies produced in a normal immune response, in which multiple clones of B cells respond to many different epitopes on an antigen
• polyenes class of antifungal drugs that bind to ergosterol to form membrane pores, disrupting fungal cell membrane integrity
• polyhedral virus virus with a three-dimensional shape with many facets
• polyhydroxybutyrate (PHB) a type of cellular inclusion surrounded by a phospholipid monolayer embedded with protein
• polylinker site or multiple cloning site (MCS) a short sequence containing multiple unique restriction enzyme recognition sites that are used for inserting foreign DNA into the plasmid after restriction digestion of both the foreign DNA and the plasmid
• polymer macromolecule composed of individual units, monomers, that bind together like building blocks.
• polymerase chain reaction (PCR) an in vitro molecular technique that rapidly amplifies the number of copies of specific DNA sequences to make the amplified DNA available for other analyses
• polymorphonuclear neutrophil (PMN) see neutrophils
• polymyxins lipophilic polypeptide antibiotics that target the lipopolysaccharide component of gram-negative bacteria and ultimately disrupt the integrity of their outer and inner membranes
• polypeptide polymer having from approximately 20 to 50 amino acids
• polyphyletic refers to a grouping of organisms that is not descended from a single common ancestor
• polyribosome (polysome) structure including an mRNA molecule that is being translated by multiple ribosomes concurrently
• polysaccharide polymer composed of hundreds of monosaccharides linked together by glycosidic bonds; also called glycans
• portal of entry anatomical feature of the body through which pathogens can enter host tissue
• portal of exit anatomical feature of the body through which pathogens can leave diseased individual
• positive (+) strand viral RNA strand that acts like messenger RNA and can be directly translated inside the host cell
• positive stain a stain that colors the structure of interest
• pour plate method a technique used for inoculating plates with diluted bacterial samples for the purpose of cell counting; cells are mixed with warm liquid agar before being poured into Petri dishes
• praziquantel antihelminthic drug that induces a calcium influx into tapeworms, leading to spasm and paralysis
• precipitin complex lattice of antibody and antigen that becomes too large to stay in solution
• precipitin ring test assay in which layers of antisera and antigen in a test tube form precipitin at the interface of the two solutions
• prevalence the total number or proportion of individuals in a population ill with a specific disease
• primary amoebic meningoencephalitis (PAM) acute and deadly parasitic infection of brain tissues by the amoeba Naegleria fowleri
• primary antibody in a sandwich ELISA, the antibody that is attached to wells of a microtiter plate to capture antigen from a solution, or in an indirect ELISA, the antigen-specific antibody present in a patient’s serum
• primary cell culture cells taken directly from an animal or plant and cultured in vitro
• primary immunodeficiency genetic condition that results in impaired immune function
• primary infection initial infection produced by a pathogen
• primary lymphoid tissue one of two types of lymphatic tissue; comprises bone marrow and the thymus
• primary pathogen microorganism that can cause disease in the host regardless of the effectiveness of the host’s immune system
• primary response the adaptive immune response produced upon first exposure to a specific antigen
• primary stain refers, in differential staining techniques, to the first dye added to the specimen
• primary structure bonding sequence of amino acids in a polypeptide chain protein macromolecule that results when the number of amino acids linked together becomes very large, or when multiple polypeptides are used as building subunits
• primary transcript RNA molecule directly synthesized by RNA polymerase in eukaryotes before undergoing the additional processing required to become a mature mRNA molecule
• primase RNA polymerase enzyme that synthesizes the RNA primer required to initiate DNA synthesis
• primer short complementary sequence of five to 10 RNA nucleotides synthesized on the template strand by primase that provides a free 3’-OH group to which DNA polymerase can add DNA nucleotides
• prion acellular infectious particle consisting of just proteins that can cause progressive diseases in animals and humans
• prodromal period second stage of acute disease, during which the pathogen continues to multiply in the host and nonspecific signs and symptoms become observable
• progeny virus newly assembled virions ready for release outside the cell
• proglottid body segment of a cestode (tapeworm)
• prokaryote an organism whose cell structure does not include a membrane-bound nucleus
• prokaryotic cell a cell lacking a nucleus bound by a complex nuclear membrane
• promoter DNA sequence onto which the transcription machinery binds to initiate transcription
• propagated spread the progression of an infectious disease from person to person, either indirectly or directly, through a population of susceptible individuals as one infected individual transmits the agent to others, who transmit it to others yet again
• prophage phage genome that has incorporated into the host genome
• prospective study a research design that follows cases from the beginning of the study through time to associate measured variables with outcomes
• prostate gland gland that contributes fluid to semen
• prostatitis inflammation of the prostate gland
• protease enzyme involved in protein catabolism that removes individual amino acids from the ends of peptide chains
• protease inhibitor class of antiviral drugs, used in HIV therapy and hepatitis C therapy, that inhibits viral-specific proteases, preventing viral maturation
• protein signature an array of proteins expressed by a cell or tissue under a specific condition
• Proteobacteria phylum of gram-negative bacteria
• proteomic analysis study of all accumulated proteins of an organism
• proteomics the study of the entire complement of proteins in an organism; involves monitoring differences in gene expression patterns between cells at the protein level
• protists informal name for diverse group of eukaryotic organisms, including unicellular, colonial, and multicellular types that lack specialized tissues
• proton motive force electrochemical gradient formed by the accumulation of hydrogen ions (also known as protons) on one side of a membrane relative to the other protozoan (plural: protozoa) a unicellular eukaryotic organism, usually motile
• protozoans informal term for some protists, generally those that are nonphotosynthetic, unicellular, and motile protozoology the study of protozoa
• provirus animal virus genome that has integrated into the host chromosome
• pseudohyphae short chains of yeast cells stuck together
• pseudomembrane grayish layer of dead cells, pus, fibrin, red blood cells, and bacteria that forms on mucous membranes of the nasal cavity, tonsils, pharynx, and larynx of individuals with diphtheria
• pseudomembranous colitis inflammation of the large intestine with the formation of a pseudomembrane; caused by C. difficile
• pseudopodia temporary projections involved in ameboid movement; these “false feet” form by gel-sol cycling of actin polymerization/depolymerization
• psittacosis zoonotic Chlamydophila infection from birds that causes a rare form of pneumonia
• psoriasis autoimmune disease involving inflammatory reactions in and thickening of skin
• psychrophile a microorganism that grows best at cold temperatures; most have an optimum growth temperature of about 15 °C and can survive temperatures below 0 °C; most cannot survive temperatures above 20 °C
• psychrotroph a microorganism that grows best at cool temperatures, typically between about 4 °C and 25 °C, with optimum growth at about 20 °C
• puerperal sepsis sepsis associated with a bacterial infection incurred by a woman during or after childbirth
• purines nitrogenous bases containing a double-ring structure with a six-carbon ring fused to a five-carbon ring; includes adenine and guanine
• purple nonsulfur bacteria phototrophic bacteria that are similar to purple sulfur bacteria except they use hydrogen rather than hydrogen sulfide for oxidation
• purple sulfur bacteria phototrophic bacteria that oxidize hydrogen sulfide into elemental sulfur and sulfuric acid; their purple color is due to the pigments bacteriochlorophylls and carotenoids
• purulent an infection that produces pus; suppurative
• pus accumulation of dead pathogens, neutrophils, tissue fluid, and other bystander cells that may have been killed by phagocytes at the site of an infection
• pyelonephritis an infection of one or both kidneys
• pyocyanin blue pigments produced by some strains of Pseudomonas aeruginosa
• pyoderma any suppurative (pus-producing) infection of the skin
• pyoverdin a water-soluble, yellow-green or yellow-brown pigment produced by some strains of Pseudomonas aeruginosa
• pyrimidines nitrogenous bases containing a single six-carbon ring; includes cytosine and thymine in DNA
• pyrophosphate (PPi) two connected phosphate groups in solution
• pyuria pus or white blood cells in the urine