Micro Vocab

Transformation

Horizontal gene transfer in which a bacterium takes up naked DNA from its environment.

Transduction

Horizontal gene transfer in which a bacteriophage transfers bacterial DNA from one cell to another.

Generalized transduction

A bacteriophage accidentally packages bacterial DNA and transfers it to another bacterium; potentially any bacterial gene can be transferred.

Specialized transduction

A bacteriophage transfers specific bacterial genes near the site where its viral DNA was integrated into the bacterial chromosome.

Conjugation

directly transfers genetic material—usually a plasmid—to another bacterium through physical contact

Hfr conjugation

Conjugation in which an integrated F factor allows a donor bacterium to transfer chromosomal genes to a recipient.

Plasmid

An extrachromosomal DNA molecule that replicates independently of the bacterial chromosome, often carrying accessory genes.

Naked DNA

DNA that is free in the environment rather than enclosed within a cell or virus.

Bacteriophage

A virus that infects bacteria and can transfer bacterial DNA through transduction.

Prokaryotic chromosome

Usually a single, circular DNA molecule located in the nucleoid; bacteria lack a membrane

Eukaryotic DNA

DNA primarily organized into multiple linear chromosomes inside a membrane

Broad

spectrum antimicrobial

Superinfection

A new infection or overgrowth of a microorganism that occurs when antimicrobial treatment disrupts normal microbiota.

Candida albicans

A yeast that normally may inhabit the human body but can overgrow and cause opportunistic infections, especially after broad

Normal microbiota (resident microbiota)

Microorganisms that normally live on or in the body and can help prevent pathogen colonization, but may cause disease under certain conditions.

Transient flora

Microorganisms temporarily present on the body that do not normally establish a lasting population.

Opportunistic pathogen

A microorganism that causes disease when host defenses are weakened, normal microbiota are disrupted, or it enters an unusual body site.

Mutualism

A relationship between organisms in which both benefit.

Decimal reduction time (D value)

The time required under specified conditions to kill 90% of a microbial population, equivalent to a 1

Microbial death rate

The rate at which microorganisms in a population are killed during a microbial control treatment.

Desiccation

The removal of water; it inhibits microbial growth, although some microorganisms can survive drying.

Freezing

A low

Flash pasteurization

A short heat treatment used to reduce pathogens and spoilage microorganisms in liquids without sterilizing them.

Lyophilization

Freeze

Ultra

high

Generalist virus

A virus capable of infecting a broad range of host species.

Host range

The range of host species or cell types a virus can infect.

Prophage

Bacteriophage DNA integrated into a bacterial chromosome or maintained within a bacterium during the lysogenic state.

Naked virus

A virus without a lipid envelope; it consists of genetic material enclosed in a protein capsid.

Carrier

An infected individual who can transmit a pathogen to others, sometimes before symptoms appear or without developing symptoms.

Reservoir of infection

The natural habitat in which a pathogen normally lives, grows, and multiplies; it can be a human, animal, or environmental source.

Environmental reservoir

A nonliving source, such as soil or water, in which a pathogen persists.

Zoonosis

An infectious disease that is naturally transmitted between animals and humans.

Mechanical vector

An organism that passively carries a pathogen from one place or host to another without the pathogen developing inside it.

Biological vector

An organism in which a pathogen develops or reproduces as part of its life cycle before being transmitted to another host.

Fomite

An inanimate object that can carry and transmit infectious microorganisms, such as a contaminated doorknob.

Direct contact transmission

Pathogen transmission through direct physical contact between an infected source and a susceptible host.

Indirect contact transmission

Pathogen transmission through a contaminated object or intermediary, such as a fomite.

Droplet transmission

Spread through relatively large respiratory droplets that travel short distances, usually during coughing, sneezing, or talking.

Airborne transmission

Spread through smaller particles that can remain suspended in the air and travel farther than typical respiratory droplets.

Foodborne transmission

Transmission through contaminated food that is ingested.

Waterborne transmission

Transmission through contaminated water.

Infection

The entry, establishment, and multiplication of a microorganism in or on a host; infection does not always cause symptoms.

Disease

A disruption of normal body structure or function that produces signs or symptoms.

Morbidity

The state or rate of illness in a population.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence

The degree or severity of disease

Nosocomial infection (healthcare

associated infection)

Contamination

The presence of microorganisms on a surface, object, or body site; it does not necessarily mean an infection has occurred.

Endotoxin

Lipopolysaccharide (LPS), particularly its lipid A component, associated with the outer membrane of Gram

Endotoxic shock

A potentially life

Exotoxin

A toxic protein produced and released by certain bacteria that damages host cells or disrupts body functions.

Gram

negative bacteria

Gram

positive bacteria

Capsule

An organized outer layer surrounding some bacteria that can help them evade phagocytosis and increase virulence.

Extracellular enzymes

Microbial enzymes released outside cells that help pathogens invade tissues, obtain nutrients, or spread through the host.

Adhesion factors (adhesins)

Microbial structures or molecules that help pathogens attach to host cells and tissues.

Antiphagocytic factors

Microbial features, such as capsules, that help pathogens avoid being engulfed and destroyed by phagocytes.

Phagocytosis

The process by which immune cells engulf and digest microorganisms or other particles.

Virulence factors

Microbial structures or products, including toxins, adhesins, capsules, and extracellular enzymes, that help a pathogen cause disease.