Protein commonly found in eukaryotic cells as part of the cytoskeleton that can form filaments (fibres).

active immunization

Intended activation of the adaptive immune response by administration of a vaccine. Immunizations are among the most effective preventive measures in medicine. Active immunization with living or inactivated vaccine induces development of pathogen-specific memory cells that allow a rapid and specific immune response when re-exposed to the pathogen. In most cases, being vaccinated once conveys life-long protection.

adaptive immunity

Defense system against pathogens acquired after having been infected. Made up of B cells and T cells, adaptive immunity is capable of “remembering” individual pathogens and protecting the body against them in case of re-exposure.


Common viruses with a DNA genome known to cause diseases of the airways and digestive organs. In gene technology, low-virulence strains of adenovirus are used as vectors in gene transfer.


In bacteriology, a term used to describe the process of a bacterium attaching to an organic or inorganic surface, to other bacteria, or to a host cell. Plays a central role in infection.


A substance administered along with the antigen as part of a vaccine in order to amplify the immune response to that antigen.


“Acquired Immunodeficiency Syndrome”; Caused by infection with human immunodeficiency virus (HIV). The virus is transmitted through direct contact with certain bodily fluids of an infected person. In countries with adequate health care, AIDS has become a treatable chronic illness although to date there is no cure or vaccine. In 2010, 1.8 million people died of AIDS.


Solution-finding process using a precisely defined methodology to solve a problem in a finite number of steps. Examples include a washing machine programme or a software program to fill out a form.


Defense response against a normally harmless environmental antigen called an allergen. Characterized by a strong inflammatory response, which can produce symptoms like a rash, hay fever, asthma, vomitingdiarrhea and even circulatory shock. An allergy is caused by overactivation of certain types of white blood cells (mast cells and basophilic granulocytes) mediated by the antibody immunoglobulin E (IgE).

amino acid

Organic molecule. Amino acids are the basic building blocks of proteins.


Protein-containing deposit in tissues. Amyloid formation is pathological: normal body proteins undergo structural changes to form fibrils followed by amyloids.


Umbrella term for drugs that are effective against bacteria, viruses, fungi, or parasites. Scientists are investigating natural substances, specifically those produced by microorganisms, for their potential anti-infective properties.


Bactericidal or bacteriostatic drug capable of killing bacteria or inhibiting bacterial growth, respectively. Antibiotics are used in the fight against bacterial infections. As an increasing number of germs is developing antibiotic resistance, scientists are constantly searching for new candidate antibiotics. The oldest and most well-known antibiotic is penicillin, derived from the fungus Penicillium chrysogenum, which interferes with bacterial cell division.

antibiotic resistance

Bacterial defense mechanism against antibiotics. Resistance may consist of an antibiotic being inactivated with the help of enzymes or of an antibiotic being extruded from the cell using different transport mechanisms before it can unfold its pharmacologic potential. Genes that bestow resistance are often found on a plasmid-a circular piece of bacterial DNA that is separate from the bacterial chromosome. Since bacteria are capable of exchanging plasmids with each other, antibiotic resistance genes can quickly be passed on. This way, antibiotics are gradually rendered ineffective.


Also known as immunoglobulins, these proteins are made by B cells in response to antigens and are released into the blood and lymph. Antibodies can attach to foreign invaders and prompt an immune response, which results in elimination of the foreign substance. They do this by recognizing specific regions of the antigen called epitopes.

antigen-specific cell

Defender cell of the immune system capable of recognizing a specific structural property of the pathogen called the antigen.


Structures that are recognized and bound by antibodies. Most antigens are proteins but may also be made from carbohydrates, lipids, and other substances. In case of an autoimmune disease, the immune system views the body’s own structures as foreign – in which case they are called auto-antigens.


Cell death which follows a genetically encoded programme. This cellular “suicide” programme is important in multicellular organisms, where it serves the purpose of getting rid of cells that are no longer needed, diseased, or infected.


A device used to sterilize laboratory equipment. Gene technology laboratory safety policy requires that all equipment used as well as contaminated waste products be sterilized. An autoclave consists of a gastight pressure container similar to a pressure cooker. The equipment is sterlized in 121 degree C hot water vapor and at 2 bar pressure.

autoimmune disease

A disease that is triggered by the adaptive immune system inappropriately mounting a response against a self-antigen. The immune system mistakes the body’s own tissues for a foreign object and attacks it. Examples include type I Diabetes mellitus and Morbus Crohn.


Chemical signaling substance used by bacteria in quorum sensing, which allows bacteria to communicate with each other and to adapt gene expression to the bacterial population’s density.


Degradation of cellular components. Cells use autophagy to break down proteins that are misfolded or no longer leeded as well as microorganisms or viruses that have entered the cell. The latter shows the importance of this process in the immune defense.

avian flu

Zoonosis caused by the influenza virus. Natural reservoirs include marine birds. 1997 saw the first documented case of the H5N1 viral subtype jumping species from birds to humans. Such a rare infection follows human contact with infected animals. So far, there have been no reported cases of a person-to-person transmission of H5N1.

B cells

Also known as B lymphocytes, these are the cells that, along with T cells, constitute the adaptive immune system. Upon activation by an encounter of antigen, they differentiate into plasma cells, which produce antibodies. In birds, antibodies are produced inside the Bursa fabricii, hence their name. In humans, they are made in the bone marrow. Humans have about 10 billions different types of B cells capable of recognizing different antigens.

Bacillus anthracis

The anthrax pathogen. This bacterium can outlast decades in the soil in the form of spores. Once it has entered the body through inhalation or an open wound, it causes extensive damage by releasing anthrax toxin.


Microorganisms that proliferate by cellular division and that lack a nucleus. They are, therefore, considered to be prokaryotes. They are classified according to the structure of their cell wall as either gram-positive or gram-negative. Many bacteria live inside our bodies where they are integral to our health, while others are pathogenic and may cause disease. One species used in the laboratory as a model organism is Escherichia coli.


Viruses that infect bacteria. Bacteriophages can be used in the laboratory to introduce genes into bacteria.


Chemical degradation of organic materials in a biological manner, for example, by microorganisms.


A slime-coated community of bacteria or fungi found adhering to surfaces. Inside the body, they use their slime coating to evade detection by the immune system and to shield themselves against antibiotics. Biofilms play a role in dental caries and occur on implants and catheters. Scientists are searching for ways to dissolve biofilms to prevent serious infections.

biologically active substance

Substance that triggers a response in living organisms.

blood clotting

Vital and rapid process to prevent excessive blood loss following an injury which mediates wound healing. Vessels constrict immediately following the injury. Platelets (thrombocytes) adhere to the site of injury and stick to each other. This clot is reinforced by a web made of fibrin fibersAn entire cascade of clotting factors is involved in this process. Genetic defects can lead to an increased tendency to bleed (hemophilia) or blood clotting (thrombosis).


The border between the central nervous system and the systemic circulation aimed at protecting nervous tissue from potentially toxic substances. Involved in transport of important molecules and maintenance of a stable internal environment.


Cancer develops when a body cell divides uncontrollably and displaces healthy tissue. It is one of the most frequent causes of death. Different factors like cigarette smoking, certain chemicals, and exposure to UV light are associated with the development of cancer and are thus considered carcinogenic. Certain viruses, like papillomavirus, can also be triggers. Cell culture exploits the fact that cancer cells don’t die. See HeLa cells.


Thin tube that is introduced into the body for diagnostic or therapeutic purposes. It allows for probing or rinsing of hollow internal organs like the urinary bladder, the stomach, the intestine, the ear, or the heart and blood vessels. In addition, it allows for the introduction of drugs or surgical equipment into the body.

cell culture

Growing living cells in a nutrient medium. Cell cultures can be used to study processes taking place inside living cells or to make biological products like monoclonal antibodies. Scientists use immortalized cell lines that divide infinitely. In most cases, these are tumour cells. The best known examples are HeLa cells.


Form of therapy used in the treatment of cancer. Cytotoxic drugs that damage cells attack all those cells that divide rapidly, a property of cancer cells and certain normal cells like bone marrow cells and hair follicles. Since chemotherapeutic drugs are unable to distinguish between healthy and cancer cells, immunosuppression and hair loss are common side effects of chemotherapy.

childhood illnesses

Diseases with a high epidemic rate, which often result in life-long immunity. This is why they are typically only seen in children. Childhood illnesses include different kinds of infectious diseases like the measles, mumps, rubella, scarlet fever, whooping cough, or chickenpox. Today, we have vaccines against most childhood illnesses.


Serious diarrheal disease triggered by the bacterium Vibrio cholerae. The bacterium spreads through contaminated water and food. As is true for many diarrheal diseases, cholera related fluid loss is the most serious threat to the body.


Cells or organisms that have originated from repeated division of a common precursor cell or organism.

complement system

System consisting of about 20 plasma proteins called complement factors involved in the body’s non-specific defense against pathogens. It is part of the innate immune system. Activated complement factors cause the pathogen to burst or attract immune cells that destroy the pathogen.

contact infection

Direct transmission of pathogens through contact with an infected person or indirect transmission through contact of contaminated objects (doorknobs, banisters, etc.), formerly also known as a smear infection.


A patient is infectious.


Acronym for “chronic obstructive pulmonary disease.”
Collective term for chronic lung diseases that impair airflow in the lungs. Characteristic symptoms include coughing, increased sputum, and dyspnoea following exertion. According to a World Health Organization prognosis, COPD could become the third most common cause of death worldwide by the year 2030.


Proteins that influence the behaviour of other cells, in particular their growth and differentiation.


Dynamic system of protein fibers inside eukaryotic cells, which gives the cell its shape and allows directional movement. It plays an important role in transport processes within the cell as well as during cell division.


Biological variation of species on earth, genetic variation and variation of ecosystems.


Deoxyribonucleic acid is a macromolecule which stores the cell’s genetic information and passes it on to the next generation. DNA contains the genetic code, the blueprint for protein synthesis.

droplet infection

Infection through contact with pathogen-containing droplets or aerosols, spread by the infected person during speaking, coughing, or sneezing. Tiny aerosols can remain suspended for hours and represent a source of infection. Influenza and tuberculosis are transmitted this way.

E. coli

See Escherichia coli.


Haemorrhagic (i.e. triggering bleeding) and frequently lethal fever triggered by the highly contagious Ebola virus. To date, there is no vaccine against ebola and no specific treatment.


Field of biology concerned with the study of the interactions between organisms and between them and their environment.


Enterohaemorrhagic (i.e. causing intestinal bleeding) Escherichia coli, the pathogenic variant of the usually harmless intestinal inhabitant, Escherichia coli. These bacteria produce a cellular toxin that causes inflammatory-like reactions inside intestinal cells that seriously damage the body. Around ten percent of patients develop haemolytic-uremic syndrome (HUS) which destroys red blood cells and can lead to acute renal failure.


Local but not temporal high incidence of a given infectious disease in a particular region or population.


The locally and temporally limited occurrence of an infectious disease.


The study of the etiology, risk factors, distribution, and consequences of disease. Infectious disease epidemiology studies these factors as they pertain to communicable diseases.


Specific region of an antigen that attaches to antigen receptors on T and B cells and to antibodies.


Small red blood cell involved in the transport of oxygen to the tissues and of carbon dioxide away from the tissues. Its color is due to the reddish oxygen-carrying protein haemoglobin. Erythrocytes do not contain a nucleus.

Escherichia coli

Escherichia coli (E. coli) is a rod-shaped bacterium that is naturally found in the intestine. E. coli is a popular model organism used in the lab. In addition to harmless intestinal inhabitant there do exist pathogenic variants like EHEC.


Unicellular or multicellular organisms that contain a nucleus. Humans, animals, plants, and protozoa are eukaryotes. In contrast, prokaryotes lack a nucleus.

flow cytometry

A method of cellular analysis used by researchers to distinguish between different types of immune cells and to examine interesting cellular molecules. Some cytometers are capable of sorting cells according to the examined characteristics.


A kingdom of organisms comprising very diverse eukaryotes: mushrooms are as much a part of this kingdom as is the organism that causes athlete’s foot or baker’s yeast. Fungi produce substances with therapeutic potential: A mold named Penicillium chrysogenum, for example, produces the antibiotic penicillin.


(German) Acronym for the German Research Centre for Biotechnology.
In 2006, the GBF was renamed as Helmholtz Centre for Infection Research (HZI).


Stretch of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) that constitutes a single hereditary informational unit. Normally, genes contain the blueprint for an organism's physical characteristics that e.g. determine what the organism will look like. The blueprint is encoded in a chemical four-letter code. In a strictly regulated way, this code is translated into a protein via the intermediate step RNA.

gene therapy

Introducing and integrating genes into the cells of an organism in order to compensate for genetic defects. Genetic defects describe missing genes or genes that have mutated and thus lost their function. In most cases, genetic defects are hereditary. Gene therapy as medical treatment is still in a developmental stage. As such, it is conceivable that a functional therapeutic gene might replace a mutated one.

genetically engineered organism

Organism whose hereditary material was intentionally altered.


See avian flu.

Haemophilus influenza

Bacterium often associated with influenza, that is found on mucous membranes, but which is not the flu pathogen. It can cause serious infections that can be lethal, especially in children. H. influenzae’s genome, sequenced in 1995, was one of the first to be sequenced completely.

HeLa cells

HeLa cells are among the most commonly used cell cultures in the lab. Their denomination derives from the name of their donor, Henrietta Lacks, an American who had developed cervical cancer. In 1951, tumour cells were extracted from her body and these cells continued to proliferate in the culture dish. That way, the first human cell line was established. Today, this immortal cell line is used all over the world in medical and cell biology research.

Helicobacter pylori

Bacterium that causes gastric ulcers and which, in chronic infections, can contribute to the development of gastric carcinoma. It was previously thought that the stomach’s acidic environment kills all bacteria. However, Helicobacter pylori invades the gastric mucosa, where it produces ammonia, a strong base, which neutralizes the stomach acid in the bacterium’s vicinity.


Inflammation of the liver which may be caused by one of five hepatitis viruses: A, B, C, D, or E. Whereas A and E are food-borne, the other types are transmitted through contaminated body fluids. Hepatitis B and C can both lead to chronic illness and are the main cause of cirrhosis and cancer of the liver. An acute hepatitis infection can lead to characteristic jaundice, where the skin and mucous membranes turn yellow. Other symptoms include nausea, fever, fatigue, and muscle aches. Vaccines only exist against hepatitis A and B.


Human immunodeficiency virus. The virus belongs to the family of retroviruses. It infects human T helper cells, which compromises the immune defense and, after several years, causes AIDS.


Biochemical messenger substance with a highly specific effect, secreted from glands into the bloodstream and acting on distant target cells. Examples include thyroid hormones, adrenaline, and the sex hormones testosterone and estrogen.

hospital bug

Bacterial pathogen that is resistant to many common antibiotics. These types of germs increasingly spread in hospitals, where a lot of antibiotics are prescribed, and patients with a weakened immune system are particularly at risk. One much-feared example are MRSA's, the methicillin-resistant strains of Staphylococcus aureus. Only one of a handful of reserve antibiotics that may only be prescribed in rare exceptions will help with this bacterium.


Organism which hosts another organism or virus. This can be beneficial to the host, as is the case with a symbiotic relationship, or harm it if it is parasite infested. The advantage for the intruder lies in using the host to obtain protection or food or exploiting its protein synthesis machinery for the production of its own proteins.


Interaction between an infectious agent and the host it has infected. The host responds to the pathogen and tries to fight it off. Over the course of evolution, pathogens have often evolved mechanisms to evade the host immune response.

human pathogens

Pathogen causing disease in humans.

immune defense

Comprises all mechanisms of the immune system that serve the purpose of defending the body against pathogens.

immune system

Tisues, cells and molecules that are involved in the body’s defense against pathogens.


An innate or acquired functional disorder of the immune system. Innate immune defects may affect the development of immune cells like B or T cells. Acquired immune defects can be triggered by infectious diseases like AIDS but may be desirable for therapeutic purposes as in following a transplantion. See immunosuppression.


Often artificially elicited suppression of the immune response, for example, to prevent rejection of a transplanted organ.

in silico

Term to describe a computer-simulated process. See in vitro, in vivo.

in vitro

Describes a process taking place in a test tube, that is, in a controlled environment outside the organism. See in silico, in vivo.

in vivo

Describes a process taking place inside an intact cell or organism. See in silico, in vitro.


Frequency of new cases of a disease. Incidence is calculated by dividing the number of new cases of a disease within a defined time period by the total number of individuals within the population under observation.

incubation period

The time between infection with a pathogen and the onset of initial symptoms of the disease.


A pathogen’s invasion of the body and subsequent proliferation. Pathogens may be bacteria, viruses, fungi, single-celled organisms, parasites, or prions. In most cases, the immune system’s initial reaction to an infection is the mounting of an innate immune response that is frequently accompanied by an inflammatory response, followed by a response by the adaptive immune system.


A disease can be infectious.


Local accumulation of fluid and white blood cells in response to infection or injury. Inflammation has four characteristic traits: heat, pain, redness, and swelling. It may become chronic and destroy tissues.


Popularly known as “the flu,” influenza is a highly contagious disease of the airways caused by the influenza virus. Immunization is possible by influenza vaccination, which bestows protection for up to one year. Each year, influenza claims roughly 500,000 lives. The most recent large-scale pandemics include the Spanish Flu (1918-1920), the Asian Flu (1957-1958), and the Hong Kong Flu (1968-1970). See also avian flu. The term “flu” is sometimes used colloquially to describe the common cold.

influenza viruses

The flu pathogen; Influenza viruses A and B affect humans.

innate immunity

Defense system against pathogens that is present from birth. It responds non-specifically but is always available and targets foreign particles within the body. Important components include mechanical barriers like the skin, macrophages, killer cells, and interferons.


Proteins belonging to the family of cytokines that regulate the immune system. Interferons are secreted by immune cells. They are effective against viruses and interfere with tumour cell proliferation. Interferons are used in therapy.


Protein found on the surface of the bacterium Listeria monocytogenes. This bacterial protein binds to the cellular transmembrane protein E-cadherin and uses it to enter the host cell.


Entry of an infectious agent into the host cell. Viruses are not able to proliferate on their own and are thus always dependent on their host and its protein machinery. Some bacteria like Salmonella and Listeria also enter the host cell.


Enzyme that attaches a phosphate group to a specific substrate. Kinases play a central role in intracellular signal transduction.

knockout mouse

Mouse strain in which a particular gene has been purposely inactivated. From the development and metabolism of these mice, conclusions regarding a particular gene’s or protein’s function can be drawn. Scientists are using knockout mice as animal models for certain human diseases. There are also knockin mice where an additional gene is introduced: in most cases, a mouse gene is replaced by a human one.


Disease of the blood-forming (haemopoietic) system, characterized by increased production of immature white blood. They spread within the bone marrow and interfere with the formation of blood components – especially red blood cells, platelets, and functional white blood cells.


White blood cells that perform different jobs as part of the immune defense. Lymphocytes are one example of leukocytes.


Bacterial genus that includes the human pathogen Listeria monocytogenes, which enters our digestive system along with contaminated raw food. Although Listeria are widespread, the number of  diseases is low as the immune system normally fights the pathogen efficiently. If the immune system is compromised, however, meningitis or sepsis that may turn lethal could result. Pregnant women can potentially miscarry if they are infected by Listeria.


A class of white blood cells that includes B cells and T cells as well as natural killer cells.


Scavenger cells of the innate immune system. They belong to the class of cells called phagocytes.


Infectious disease caused by the single-celled parasite Plasmodium. Plasmodium spreads inside the patient’s red blood cells until they rupture. This causes the typical Malaria symptom of recurrent periodic fever. The Anopheles mosquito transmits the malaria pathogen. The disease is the primary cause of death of children in Africa. To date, a vaccine does not exist.


Highly contagious childhood disease that is transmitted by droplet infection with Paramyxovirus, and which is accompanied by fever and body-wide rashes. Although a safe and effective vaccine is available, in countries with inadequate health care, many children still die from this infectious disease.


Reddish, brown, or black pigments made from the amino acid tyrosine by enzymatic oxidation. They give colour to skin, hair, and eyes. Melanin is found in vertebrates, insects, microorganisms, plants, and in the ink of calamar. In vertebrates, melanin is synthesized by melanocytes in the skin and retina.

memory cells

Long-living B cells or T cells capable of “remembering” a prior infection. Memory cells bestow years of long-term protection following immunization.

Mendelian inheritance

Rules that describe the inheritance of traits whose expression is determined by only a single gene. Named for Gregor Mendel. Today, exceptions to these rules are well-established.


Bacterially or virally triggered inflammation of the membranes (called the meninges) that package the brain and spinal cord. Characterized by high fever, serious headaches, and a stiff neck. Meningitis can be life-threatening and is treated using antibiotics.


Study of the total genome of all microorganisms and viruses of a certain biotope. Metagenomics provides information about the hereditary material of microorganisms that cannot be grown in pure culture.

minimal infectious dose

The minimum amount of pathogen that must be transmitted to trigger an infection. This dose is pathogen-dependent.

model organism

Organism used by scientists to study biological mechanisms, e.g. of infectious diseases, and how to prevent or treat them. Examples include the fruit fly D. melanogaster, the zebrafish D. rerio, the nematode C. elegans, the bacterium E. coli, and mice. See also knockout mice.

monoclonal antibodies

Produced by an individual clone of B cells, monoclonal antibodies all recognize the same exact epitope. They are used in medical diagnostics and research and partially also in the treatment of diseases.


In cell biology, describes movements of the whole cells (for example, of lymphocytes) or within the cytoplasm.

mouse inbred strain

Mice with an identical genetic profile.   


Abbreviation for Methicillin-resistant Staphylococcus aureus. Infections with this bacterium are difficult to treat because they can resist numerous antibiotics.

mucous membrane

Also called mucosa, this protective layer lines the inner surfaces of hollow organs. Mucosa often contains glands that secrete mucus.


A term which describes a germ that is resistant to several different types of drugs.


Bacterial species that includes a number of pathogens: Mycobacterium tuberculosis causes tuberculosis, Mycobacterium leprae causes leprosy. The bacterium’s unique cell wall structure makes it largely insensitive to a number of different antibiotics.


Non-pathogenic bacteria that live in the soil and that exhibit social behavior by forming communities consisting of thousands of cells. They produce natural substances some of which can be used as therapeutics.

natural killer cells

Lymphocytes capable of destroying virus-infected cells and tumour cells without prior stimulation. They are part of the innate immune response.


Cell death prompted by external factors that trigger an inadequate supply of oxygen, or by toxic substances. As this cell death is not regulated as opposed to apoptosis, it frequently leads to localized inflammation.

nosocomial infection

Infection with a typicallymulti-resistant hospital bug. Due to frequent use of antibiotics, many germs that are resistant against conventional antibiotics are found in doctors’ offices and hospitals.

nuclear magnetic resonance spectroscopy

Short: NMR spectroscopy. Analytic tool that exploits the magnetic properties of atomic nuclei and yields information about a given molecule's structure and chemical environment.

obligation to report

Obligation to report dangerous diseases to the local health authorities or the Robert Koch Institute (RKI). An insight into the current distribution of diseases that require reporting to the authorities can be found in the RKI’s Epidemiological Bulletin. Cholera, the measles, and the plague are among the diseases with an obligation to report.


Gene encoding the blueprint for a cancer-causing or cancer-promoting protein. In most cases, a mutant version of a gene regulating the cell cycle or controlling cellular growth.

opportunistic human pathogens

Organisms which are only pathogenic under certain circumstances. Healthy people with an intact immune system cannot get sick from them. Patients with a weakened immune system, however, cannot defend themselves sufficiently against these pathogens.

oral vaccination

Orally administered vaccine. Most vaccines do not survive passage through the digestive tract, making only a handful of vaccines suitable for this type of administration. The most famous example of an oral vaccination is the polio vaccination, which helped eradicate the disease in Europe.

organic molecules

With few exceptions, the compounds formed by the element carbon with itself and with other elements, specifically hydrogen, oxygen, nitrogen, and the halogens. All biological building blocks are organic molecules.


The spread of an infectious disease across borders and continents.


Viruses, which infect the skin and mucous membranes and which can lead to development of tumours. While these may just be a benign wart, papillomaviruses are also known for causing cervical cancer.


Organism which lives at the expense of another, larger host organism. In most cases, the parasite harms but, as a rule, doesn’t kill the host. Examples of parasites include many species of worms and tics, but also the pathogens causing toxoplasmosis or malaria.

passive immunization

Emergency measure used in case of risk of a serious infection. Antibodies against the pathogen are injected into the body but the immune system does not make its own antibodies or memory cells. Vaccines can be administered intramuscularly (i.e. injected into a muscle) or subcutaneously (i.e. injected into the hypodermis) or they may be given orally.


Causing disease.


Ability of a pathogenic species to cause disease by infection.


Germs that cause disease in their host organism. If the host is human, the germ is referred to as a human pathogen.


Method used to amplify DNA sequences in vitro. PCR exploits the properties of the enzyme DNA polymerase to synthesize a complementary strand of DNA from a template strand. Scientists can specify which segments the polymerase enzyme is to copy. The method is particularly useful when only small amounts of DNA are available. Popular tool used in diagnostics, molecular biology, forensics, and archaeology.


Short chain of amino acid building blocks.


Scavenger cells of the defense system, which protect the body by ingesting bacteria, foreign particles, and dead cells and enzymatically breaking them down.


Infectious disease caused by the bacterium Yersinia pestis, which, during the Middle Ages in Europe, claimed millions of lives. Today, the disease continues to pose a threat in some countries. The plague is an example of a zoonosis – the disease is transmitted from rat flea to human.

plasma cells

Differentiated B cells that produce antibodies and release them to their environment.

plasma membrane

Biological membrane which surrounds the living cell. It is made of a lipid bilayer and shields the cell from its environment.


Small circular piece of DNA which replicates independent of the genome. Plasmids are used in molecular biology as “gene ferries” that transport DNA.


Short for poliomyelitis, this disease of the nervous system caused by the polio virus may lead to paralysis. Children under the age of five are especially at risk. There is no treatment available, but a prophylactic oral vaccine does exist. Today, thanks to concerted global efforts, polio only still exists in three countries.

polyclonal antibodies

In contrast to monoclonal antibodies, polyclonal antibodies are made by many different B cells. They target the same antigen but recognize different regions of the antigen, in other words, different epitopes. They are obtained from the blood of animals that were vaccinated and are used in research as well as in passive immunizations.

polymerase chain reaction (PCR)

Method used to amplify DNA sequences in vitro. PCR exploits the properties of the enzyme DNA polymerase to synthesize a complementary strand of DNA from a template strand. Scientists can specify which segments the polymerase enzyme is to copy. The method is particularly useful when only small amounts of DNA are available. Popular tool used in diagnostics, molecular biology, forensics, and archaeology.


A measure of the frequency of a disease at a given point in time. Prevalence is calculated by dividing the number with the disease by the number of people in the population.

primary infection

First contact between a pathogen and the immune system.


Infectious abnormal variant of a protein which proliferates inside a host by forcing normal proteins of the same type to assume the abnormal form. Prion diseases include bovine spongiform encelphalopathy (BSE) in cows, scrapie in sheep, and Creutzfeldt-Jakob-disease in humans.


Microorganisms whose genetic material is not enclosed by a nuclear membrane as it is in eukaryotes. Bacteria and archaea are examples of prokaryotes.


Preventive measure against a disease, e.g. a vaccine.


Most important basic building block of a cell. Proteins are a class of macromolecules that give the cell its structure, interconvert chemical substances, receive signals, are messenger substances, or act as antibodies as part of the immune defense. Proteins are made up of amino acids that are arranged like pearls on a string. This string coils and folds upon itself until it gives rise to the shape the protein needs to be able to fulfil its function in the body. The information about the amino acid sequence in a protein is encoded by the corresponding gene.


The totality of all proteins in a cell or organism at a given point in time. Because new proteins are constantly being made and old ones degraded, the proteome’s composition is constantly changing. Scientists conduct proteome research e.g. to better understand what happens in the body during an infection.


A genus of rod-shaped, Gram-negative bacteria with flagella. Found in nearly every type of environment. Pseudomonas include the species Pseudomonas aeruginosa, which causes disease in people with a weakened immune system.

Pseudomonas aeruginosa

See pseudomonas.

quorum sensing

Chemical mode of communication used by many bacteria to influence which genes are switched on or off depending on the surrounding bacterial density. They do so by releasing a substance called an autoinducer to their environment. At the same time, they carry a molecule on their surface capable of recognizing autoinducers produced by other neighbouring bacteria. Some species of insects also use this mode of communication.


Protein that specifically recognizes and binds a certain molecule. Receptors are found inside cells and on the cell surface. They are an important component of cellular signal transduction.


See antibiotic resistance.


RNA-containing viruses. Following an infection, the RNA hereditary material is transcribed into DNA and becomes integrated into the host genome, where it is treated as part of the body’s own DNA, copied and used as a template for protein production by the cell’s protein-making machinery. HIV is an example of a retrovirus. Retroviruses are frequently used in gene technology to introduce genes into cells.


Acronym, which stands for ribonucleic acid; macromolecule involved in coding and reading genes or in protein synthesis. RNA is made of a chain of building blocks called nucleotides, which “translate” the information contained in DNA into instructions for making a protein. Biologists distinguish between messenger, transfer, and ribosomal RNA.

Robert Koch-Institute (RKI)

Federal biomedical institution in Germany. The most important areas of work include recognition of and fight against infectious diseases as well as analysis of long-term health trends within the population.


Bacterial species that can cause typhoid and salmonellosis. Salmonellosis is a very common diarrheal disease that is transmitted by ingesting contaminated animal products. It represents a major health threat for very young and older patients or for persons with an immune deficiency. Symptoms of typhoid include fever and abdominal pain and can be lethal if untreated.


Severe acute respiratory syndrome; a highly virulent form of pneumonia caused by the corona virus. A 2003 SARS epidemic spread rapidly from Asia to Europe and America through air traffic. 8,000 cases were reported worldwide. Because of the short incubation period, patients could be quickly identified and isolated, which helped contain the epidemic.


Systematic test protocol for examining a large number of samples or people for certain properties.


Infection of the blood circulatory system, which is often lethal. Sepsis develops if a pathogen or a toxin produced by it gets into the bloodstream and spreads throughout the body. This prompts activation of the entire immune system, leading to unchecked inflammation, a massive drop in blood pressure, and multiple organ failure.


Determining the base sequence in DNA or RNA to decode the hereditary information it contains. The term is also used to describe the amino acid sequence in a protein.

serological test

Antibody-antigen-test used to determine blood group and diagnose disease by testing for the presence of antibodies against a particular infectious agent.


Bacterial genus which may cause bacillary dysentery (shigellosis). The disease is transmitted through contaminated water or food and is characterized by fever and severe diarrhea.

signal transduction

Transmission of an usually external signal inside the cell or organism. Receptors, enzymes, and messenger substances all figure prominently in this process. Signals can be combined, amplified, or attenuated. By studying these information processes, researchers are gleaning insights into the inner workings of a cell.

single-celled organisms

Organisms made up of just one single cell that, unlike bacteria, contain a true nucleus and are thus classified as eukaryotes. Examples include paramecium and the pathogen that causes malaria.


Serious viral infectious disease. Typical symptoms include skin pustules. Smallpox are a prime example of a successful immunization campaign: First attempts at creating a vaccine were made by Edward Jenner in the 1700's. He immunized patients using extracts from bovine smallpox which are caused by a closely related virus. Patients were immune to human smallpox following this vaccine. Mass immunizations led to smallpox being officially declared eradicated by 1980. Today, only two high-security laboratories store frozen viral cultures.

smear infection

Infection through contact with contaminated surfaces.

source of infection

The origin of an infection.

spot synthesis

Method developed at the GBF for parallel synthesis of peptides, short chains of amino acids, on a cellulose membrane.


Spherical, gram-positive bacteria that colonize skin and mucous membranes and which can cause disease.

Staphylococcus aureus

Bacterium that lives on the skin and mucous membranes in many people. In case of a compromised immune system, the opportunistic human pathogen causes wound infections and muscular disorders. It can also lead to an often deadly intoxication of the circulatory system. MRSA's, multiresistant strains of the bacterium, are much-feared.

stem cell

Relatively undifferentiated cell which has the capacity to divide indefinitely and in the process produce daughter cells, which themselves become stem cells or differentiate into specialized cell types.


Devoid of viable microorganisms.


Killing off all microorganisms and inactivating all viruses and nucleic acids found on or inside of an object. See autoclave.


German Standing Committee on Vaccination; independent panel of experts coordinated by the Robert Koch Institute that publishes recommendations on how to protect against infectious diseases.


A group of bacteria that causes many diseases including tonsillitis, dermatitits, dental caries, and pneumonia. Rheumatic heart disease is one dangerous potential outcome of a streptococcus infection. The bacteria are able to hide from the immune system and antibiotics inside the host tissue, making an infection challenging to treat.

Streptococcus mutans

Bacterial species of the genus streptococcus. Most important infectious agent behind dental caries, found in most people’s saliva.

structural biology

Science concerned with the study of the spatial structures of molecules. The structure allows for conclusions to be drawn as to a molecule’s function.


Predisposition of a host for a given infectious disease. Also, susceptibility of a pathogen to a particular drug.

systems immunology

Research field concerned with the analysis of experimental data using methods from informatics and computer simulation. Scientists study mechanisms employed by the immune system to respond to an infectious disease. They develop mathematical models and make predictions about future experiments.

T cells

Also called T lymphocytes, T cells, together with B cells, are part of the adaptive immune system. T cells are classified as either cytotoxic or helper T cells, which directly attack infected cells or orchestrate the immune response, respectively. Their name derives from their site of origin, the thymus.


Caused by the bacterial toxin produced by Clostridium tetani, which spreads inside wounds. Bacterial spores are found practically everywhere in the soil, which is why it is imperative to keep woundsclean. Tetanus is not transmitted from person to person. A vaccine does exist and is recommended by the Robert Koch Institute.


Blood platelets involved in blood clotting.


Lymphoid organ in the upper region of the chest, which lies immediately behind the sternum. Place of T cell development. In children, a sufficient reservoir of T cells is produced; beginning of puberty, the thymus regresses and loses its functionality.

transgenic mouse

Genetically engineered mouse whose cells contain additional, artificially introduced DNA. Transgenic mice are used to study the function and regulation of genes. They also serve as a model which helps to study human diseases more easily.


Exchange between different areas of research to facilitate processing of results in application. As such, findings from basic science research more quickly find their way into clinical research, where they undergo further testing. Questions that arise in the process are then sent back to the researchers in the lab. Translation thus helps speed up drug development, for example, which ultimately benefits patients.


Disease of the lungs caused by Mycobacterium tuberculosis, a bacterium first described by Robert Koch. Since 1990, a resurgence of the epidemic has been observed. Antibiotic-resistant strains are especially problematic. Around 1.4 million people are dying each year from “consumption.” Not everyone infected with the bacterium contracts tuberculosis. The risk is especially high in people with a weakened immune system. As such, tuberculosis is the chief cause of death in people with AIDS.




A substance or mixture of different substances used to prompt the immune system to mount a response against a given pathogen. Attenuated vaccines contain live pathogen that has been disabled in their virulent properties. Inactivated or killed vaccines are made of pathogens that have been killed off, of certain parts of pathogens, or of toxins. In many cases, an adjuvant is added to a vaccine.


A substance or mixture of different substances used to prompt the immune system to mount a response against a given pathogen. Attenuated vaccines contain live pathogen that has been disabled in their virulent properties. Inactivated or killed vaccines are made of pathogens that have been killed off, of certain parts of pathogens, or of toxins. In many cases, an adjuvant is added to a vaccine.


The extent of pathogenicity of a pathogenic strain.


A virus consists of genetic material – DNA or RNA – packaged inside a protein coat. This minimalist equipment is insufficient for the virus to replicate and the virus is therefore dependent on the presence of a host cell to be able to proliferate. Many viruses transmit diseases; a subset of them may also cause cancer.


The World Health Organization. The United Nations’ health agency is concerned with global health issues, disseminating information about diseases, and tracking and evaluating health data. The WHO's goal is to fight disease, in particular infectious diseases.

wound infection

Usually a bacterial infection of injured skin accompanied by a localized inflammatory response.


Genus of rod-shaped bacteria whose most well-known representative is Yersinia pestis, the pathogen behind pulmonary and bubonic plague. Spoiled food, specifically pork, can lead to infection with Yersinia enterocolitica, which is accompanied by diarrhea and abdominal pain. The third pathogenic species is Yersinia pseudotuberculosis, a close relative of the plague pathogen, which causes gastroenteritis.


Infectious disease transmitted from animal to human, like avian flu. The number of zoonoses is increasing because of changes in factory farming, increased mobility, and population growth.