Infectious Disease Doctor
Glossary
Microbial terminology explained
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Adjuvant A substance that enhances the immune response to the antigen with which is it mixed Antibiotic A compound that inhibits the growth and reproduction of bacteria. Antibiotics are not effective against viruses. Antibody A specialized protein produced by the immune system that helps destroy disease-causing organisms. An antibody is a component of humoral immunity. Antibodies can be effective defenders against both bacteria and viruses. An antibody must be made specifically for each pathogen. Antigen A protein or other substance capable of triggering an immune response Antiviral A compound that inhibits the growth and reproduction of viruses Aptamer Short strands of DNA or RNA that are designed to bind to certain target molecules Arthropod An invertebrate animal that has an external skeleton, a segmented body, and jointed appendages. This classification includes insects, spiders, and crustaceans. Some types, such as mosquitoes and ticks, can transmit diseases. ATP Adenosine triphosphate, a chemical in cells that transfers energy and can play a role in communication between cells. Attenuate To reduce the virulence of B Bacterium A class of microorganisms that are made of a single cell with a certain structure. While many bacteria are beneficial, some bacteria can cause disease. (plural, bacteria) Biologics A biological product used in medicine Biosafety level 3 (BSL-3) A specially designed, high-containment laboratory facility used for work with infectious disease agents that can cause severe disease or are potentially lethal. The Centers for Disease Control and Prevention has established four levels of biosafety laboratory facility, with level 4 designated for use with the most hazardous agents. Broad-spectrum antibiotic An antibiotic that is effective against a wide range of bacteria, including both gram-positive and gram-negative bacteria. Examples include ampicillin, amoxicillin, ciprofloxacin, and tetracycline. C CD4+ T cell A cell of the immune system, also known as a “helper” cell, that helps other immune system cells produce antibodies. CD4+ T cells are the cell type that are infected and destroyed by HIV. Cell The basic unit of all living things Cell-mediated immunity Part of the immune system in which specific immune system cells, such as cytotoxic T cells, directly attack infected cells Chromosome One of a segment of DNA that together make up the genetic information of an organism. Humans have 23 pairs of chromosomes. Clade A group of organisms that includes all descendants of one common ancestor Cohort Group of individuals used in a study that have a statistical factor, such as age, in common Cytokine A small protein that is secreted by certain cells of the immune system that plays an important role in cell signalling by affecting the behavior of other cells. Examples include interferon and interleukin. Cytotoxic T cell Also known as “killer” T cells, a type of immune system cell that can directly attack infected cells. D Disseminate To disperse or spread about widely DNA Deoxyribonucleic acid, the chemical structure that contains the genetic information of an organism. The double helical structure is made of two strands consisting of deoxyribose and phosphate and is held together by bonds between purine and pyrimidine bases which project inward from two chains and form the genetic code. E Enteric Infection A disease of the intestines caused by an infection that is characterized by diarrhea, vomiting, nausea, and abdominal discomfort that may result in significant loss of fluids and electrolytes. Envelope A lipid (fatty) covering that surrounds a viral particle. It is derived from the cell membrane of the host cell when the virus buds, or exits, the infected cell. The envelope is important for entry into a host cell. Viruses with an envelope are generally less stable outside of a host than viruses that lack an envelope. Viruses that are enveloped include HIV, influenza, Ebola, dengue, and chikungunya. Enzyme A protein that acts as a biological catalyst. Enzymes are necessary to produce chemical reactions within a cell. Epidemic A disease affecting a large number of individuals within a population, community, or region at the same time Epidemiologist A medical scientist who studies the incidence, distribution, and control of disease in a population Eradication The complete elimination of a disease Eukaryotes Organisms whose cells possess a membrane-bound structure called a nucleus that contains the genetic material (DNA) F Febrile Having or showing symptoms of a fever Functional genomics A field that attempts to describe the functions and interactions of genes and proteins by using genome-wide approaches (as opposed to the classic single gene approach). It combines data from DNA sequencing, gene expression, and protein function to try to understand complex processes that occur within cells. Fungi A diverse group of single-celled or multi-cellular eukaryotic organisms that decompose and feed on organic matter. Examples include yeasts, mushrooms, and mold. G Gene A sequence of genetic material that provides the information to make a specific protein. Genome The entire genetic information of an organism. Gram-negative bacteria A category of bacteria that do not produce a positive result with a violet dye staining technique (bacteria that do appear violet are referred to as gram-positive). Gram-negative bacteria include Escherichia coli, Acinetobacter, Pseudomonas, and Klebsiella. Gram-positive bacteria A category of bacteria that produce a positive result with a violet dye staining technique, due to the presence of thick layer of peptidoglycan in their cell walls (bacteria that do not appear violet are referred to as gram-negative). Gram-positive bacteria include the streptococci, staphylococci, and the bacterium that causes anthrax. H Heme A small molecule that consists of an iron atom contained in the center of a large heterocyclic ring called a porphyrin. Heme is involved in many metabolic reactions that occur in the body and is sequestered by specific heme-binding proteins such as hemoglobin. Humoral immunity Part of the immune system that provides immunity against disease-causing organisms in body fluids. The main functional unit of humoral immunity is an antibody. I Immune response The body’s immune system response that defends against attacks from disease-causing agents. The body can produce two different immune responses – humoral immunity and cell-mediated immunity. Immunity The resistance to an infectious disease agent that can be developed by prior exposure to the pathogen or through vaccination Immunogen A substance that produces an immune response Immunogenicity The ability of an antigen to elicit an immune response Immunoreactive Participating in an immune response, such as by reacting with a specific antibody, as determined by some immunological assay or technique M Macrophage A cell of the immune system that functions as one of the body’s first defenders against disease-causing organisms. Macrophages can engulf and destroy pathogens. Microbiome Also known as the microbiota, the collection of microbes that inhabits the body. Microbial cells are estimated to outnumber human cells by a factor of ten to one. The microbiome influences human health and disease. Microliter One millionth of a liter Microorganism Also called microbe, an organism of microscopic size MicroRNA A short piece of single-stranded RNA about 21 to 23 bases in length that regulates the expression of genes. MicroRNAs function by binding to a matching piece of messenger RNA that encodes a protein and decreasing the production of that protein. Morbidity The rate of disease in a population Mortality The number of deaths in a given time or place Mucosal Relating to the mucous membranes of the body. These are sites where many important pathogens, such as influenza, enter the body. N Nanometer One billionth of a meter Negative-sense RNA Viral RNA with a base sequence complementary to that of messenger RNA (mRNA). The RNA must be converted to positive-sense RNA by a viral enzyme called RNA polymerase before translation into protein can occur. Viruses that have negative-sense RNA genomes include influenza and Ebola. Neuraminidase A protein found on the surface of influenza viruses that is needed for the virus to exit the host cell and infect more cells. The action of this protein is inhibited by the class of antiviral drugs that includes the drug Tamiflu®. In the system using for naming influenza subtypes (H1N1, for example), the N stands for neuraminidase. O Oligosaccharide A carbohydrate that is composed of a small number (3 to 10) of simple sugar units linked together. P Pandemic A disease occurring over a wide geographic area and affecting a very high proportion of the population. This term is often used to describe large outbreaks of influenza that occur worldwide and cause a high rate of death. Pathogen An organism that can cause disease, such as a bacterium or a virus Pathogenic Capable of causing disease Pathogenesis The mechanism by which a certain agent causes disease Peptide Short chain of linked amino acids. Amino acids are the building blocks of proteins. Phase I clinical trial The first stage in testing new drugs or vaccines in humans. Phase I trials are performed on small numbers of people and are designed primarily to test the safety of the new drug and to obtain information about dosages. Drugs that pass phase I trials go on to trials that determine effectiveness and possible side effects and are tested on larger groups of people. If safety and effectiveness are demonstrated, the drugs or vaccines may become approved as treatments. Placebo An inert substance used in a controlled experiment to test the efficacy of another substance, such as a drug or a vaccine Plasmid A circular segment of DNA that encodes a separate set of genes than those present in chromosomes. Plasmids are most often found in bacteria, but they are also useful to scientists as vectors. Polymerase chain reaction (PCR) A technique to amplify a single or few copies of a piece of DNA by several orders of magnitude, generating millions or more copies of a particular DNA sequence Polypeptide A chain of amino acids linked together. Amino acids are the building blocks of proteins. Positive-sense RNA Viral RNA that has the same base sequence as mRNA which allows it to function as a template for protein synthesis during viral replication Probiotic Live microorganisms that are intended to have health benefits. They consist of members of the microbiota that have beneficial effects and may be used to counter the damaging effects of harmful bacteria. For example, they may help prevent diarrhea caused by some infections and antibiotics. Protein Components of cells and viruses that play structural and functional roles in cells R Reactogenicity Ability to cause an immunological reaction Reassortment The recombination or mixing of the genetic material of viruses; may occur when two different influenza virus strains infect the same cell, resulting in the formation of a new influenza virus strain Recombinant Produced by genetic engineering Recombination The process by which DNA is broken and genetic material is exchanged through the crossover of DNA between maternal and paternal chromosomes. This can result in offspring having different combinations of genes than their parents. Retrovirus A type of virus that uses RNA as its genetic material (rather than DNA). Examples include HIV and HTLV. RNA Ribo nucleic acid, a chemical structure that is related to DNA, but has only one strand and a somewhat different chemical composition. RNA performs a variety of functions in the cell and can act as a messenger to carry the genetic code from the DNA to other parts of the cell. RNA can also serve as the genetic material of some viruses. S Sepsis The body's extreme immune response to an infection that causes damage to tissues and organs and can lead to death. Its incidence appears to be increasing, in part due to drug-resistant infections. Serum The clear, amber-colored liquid that separates out when blood coagulates. It is protein-rich and contains antibodies. Single nucleotide polymorphism Variation in a single base in the genetic code between different individuals of the same species Spore A form of a microorganism, such as a bacterium, that is dormant and stable in the environment, but can become capable of reproducing after infecting an animal or person T T cell A type of white blood cell that plays an essential role in the immune system. The "T" stands for thymus which is the organ where the cells mature (as opposed to another type of white blood cell, called B cells, which mature in the bone marrow). Subsets of T cells express different receptors on the surface of the cell and perform specific functions. Also known as a T lymphocyte. Toxin A poison that produces illness by affecting bodily functions Transcription The process by which the genetic information encoded in DNA is copied into a complementary copy in RNA V Vaccination Injection of a weakened or mild form of a disease-causing agent to produce immunity Vaccine A preparation of killed or weakened microorganisms that is administered to produce or increase immunity to a particular disease Vector A segment of genetic material that is used as a vehicle to introduce specific genes into cells Virulence The ability to cause rapid and severe disease Virus A microscopic particle that is made up of genetic material (either DNA or RNA) and protein that can replicate only inside living cells Virus-like particle A particle assembled from multiple copies of the capsid protein that, like a virus, can produce an immune response, but unlike a virus, is not infectious because it does not contain genetic material Z Zoonosis A disease that is transmitted from animals to humans. The incidence of zoonoses (plural) increases when humans exist in close contact with animals and when humans encounter animals in new geographical regions. |
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A
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Adjuvant
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A substance that enhances the immune response to the antigen with which is it mixed
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Aerobic respiration
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Alga (algae, plural)
A single-celled or multicellular eukaryotic, photosynthetic organism.
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Amino acid
The basic building block of a protein.
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Antibiotic
A chemical that kills or inhibits the growth of bacteria and is used to treat bacterial infections.
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Antibody
A Y-shaped protein made by certain white blood cells which is produced by the body’s immune system in response to a foreign substance (antigen). The antibody destroys the antigen.
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Antigen
A foreign substance such as a pathogen that stimulates the body’s immune system to produce antibodies.
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Archaean (archaea, plural)
A prokaryotic, single celled organism.
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B
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Bacterium (bacteria, plural)
A prokaryotic, single celled organism.
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Binary fission
A type of asexual reproduction in which the cell divides into two separate daughter cells each with identical DNA.
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Biogas
A gas that is produced from the anaerobic (without oxygen) decomposition of organic matter.
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Bioremediation
The use of microbes to break down toxic or unwanted substances.
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Budding
A type of asexual reproduction in which an outgrowth forms from the parent cell. It then usually pinches off to form a separate independent cell.
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C
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Capsid
The protein coat surrounding a virus.
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Cell
The basic unit of all living things.
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Chlorophyll
A green photosynthetic pigment usually found in organelles called chloroplasts.
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Chromosome
A long continuous pieces of DNA that carries genetic information.
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Cilium (cilia, plural)
A tiny hair-like structure on the surface of some micro-organisms or cells which beats rhythmically to either propel trapped material out of the body, for example in the lungs, or make a free-living microbe move.
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D
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DNA
Deoxyribonucleic acid: the store of genetic information inside living cells and many viruses.
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Decomposer
The name given to some fungi and soil bacteria that break down dead animals and plants and their waste products into simpler substances called nutrients.
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E
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Enzyme
A protein that facilitates a biochemical reaction by speeding up the rate at which it takes place within cells.
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Eukaryote
A single-celled or multicellular organism which has a true membrane-bound nucleus and membrane bound organelles.
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Extremophile
A microbe that positively thrives in environments that would kill other organisms.
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F
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Fermentation
The conversion of organic compounds such as carbohydrate into simpler substances by microbes, usually under anaerobic conditions (with no oxygen present). Energy is produced.
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Flagellum (flagella, plural)
A long thin appendage present on the surface of some cells such as bacteria and protoctista which enables them to move.
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Food poisoning
Any illness caused by eating food contaminated by pathogenic microbes.
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Food spoilage
Changes in appearance, flavour, odour, and other qualities of the food due to microbial growth which causes it to deteriorate and spoil by decay.
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Fungus (fungi, plural)
A eukaryotic, non-photosynthetic, spore-forming organism. They range from single celled organisms to very complex multicellular organisms.
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G
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Gene
Basic unit of inheritance located on a chromosome. A gene is a piece of deoxyribonucleic acid (DNA) that contains the instructions for the production of a specific protein.
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Generation time
The time taken for a population of micro-organisms to double in number.
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Global warming
A rise in the temperature of the Earth’s atmosphere due to the increased emission of greenhouse gases which traps more heat in the atmosphere, causing the planet to warm up.
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H
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Host cell
A cell that is infected by a virus or another type of micro-organism.
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Hypha (hyphae, plural)
A very fine thread that is the basic structure of filamentous fungi.
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I
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Inflammation
A reaction of tissue to irritation, injury, or infection. It is a beneficial process as it destroys or contains the pathogen within a small area enabling the healing process to begin.
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L
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Lymphatic system
Lymph nodes linked by a network of small tubes spread throughout the body that transport the lymph fluid.
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Lysis
The physical rupture of a cell.
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M
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Memory cell
A cell which is produced as part of a normal immune response. These cells remember a specific antigen and are responsible for the rapid immune response, production of antibodies, on exposure to subsequent infections by that particular antigen.
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Methanogen
Micro-organism that produces methane.
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Micro-organism (microbe)
A small living thing. The group includes bacteria, archaea, protozoa, algae, fungi and viruses.
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Mould
A multicellular filamentous fungus.
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Mycelium
A branched network of fungal hyphae.
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N
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Normal body flora
Microbes that have adapted to living on the body, are usually present and rarely cause home.
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Nucleus
The nucleus is the control centre of the cell containing chromosomes.
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O
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Organelle
A membrane enclosed structure, in cells, that has a specialised function.
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P
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Pathogen
An organism that causes disease.
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Phagocyte
A white blood cell that can surround engulf (by phagocytosis) and destroy invading micro-organisms including viruses and bacteria. There are two separate groups - macrophages and neutrophils.
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Photosynthesis
A process that occurs in plants, algae and some bacteria called the cyanobacteria that traps the sun’s light energy and uses it to fix carbon dioxide into organic compounds.
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Primary producer
Green plants, algae and some bacteria called the cyanobacteria which produce their own food by a process called photosynthesis. They are found at the beginning of the food chain.
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Prokaryote
An organism that has a simple cell structure without a membrane bound nucleus or organelles.
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Protein
A folded long – chain molecule consisting of amino acids. Each protein has a special function. Proteins are required for the structure, function, and regulation of an organism’s cell/cells, tissues, and organs.
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Protozoan (protozoa, plural)
A eukaryotic, single celled organism that usually lacks chlorophyll.
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Pseudopodium (pseudopodium, plural)
A temporary extension of the cytoplasm of an amoeboid cell. It is used in both motility and feeding.
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R
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Recycling
A cyclical process by which essential elements are released into the environment where they are then reused.
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S
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Sporangium (sporagia plural)
A sac containing spores that develops from the fruiting body of a fungus.
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Spore
A general term for a dormant stage in an orgainisms life cycle. Spores enable survival of adverse conditions, distribution, and reproduction. There are many types which may be produced both asexually and sexually.
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T
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Toxin
Any substance that is poisonous to other organisms.
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V
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Vaccine
A special type of medicine that is given to both people and animals to artificially increase immunity to a particular disease and to prevent an infectious disease from developing.
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Viral envelope
A spikey coat that covers the virus’s protein coat or capsid.
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Virus
An infectious particle that relies on the cellular machinery of the host cell to grow and replicate.
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Y
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Yeast
A single-celled fungus.
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