Microbiology Core Vocabulary and Glossary

Comprehensive practice flashcards covering key terms, structures, and definitions in microbiology.

Aseptic technique

A series of steps taken to prevent contamination of laboratory cultures and media.

Cell wall

A rigid layer present outside the cytoplasmic membrane; it confers structural strength on the cell.

Chemolithotrophy

A form of metabolism in which energy is generated from the oxidation of inorganic compounds and carbon is obtained typically from $CO_2$.

Chromosome

A genetic element, usually circular in prokaryotic cells, carrying genes essential to cellular function.

Colony

A macroscopically visible population of cells growing on solid medium, arising from a single cell.

Contrast

The ability to resolve a cell or structure from its surroundings.

Culture

A collection of microbial cells grown using a nutrient medium.

Cytoplasm

The fluid portion of a cell, enclosed by the cytoplasmic membrane.

Cytoplasmic membrane

A semipermeable barrier that separates the cell interior (cytoplasm) from the environment.

Differentiation

Modification of cellular components to form a new structure, such as a spore.

Domain

One of the three main evolutionary lineages of cells: the Bacteria, the Archaea, and the Eukarya.

DNA replication

The process by which information from DNA is copied into a new strand of DNA.

Enrichment culture

A culture that employs highly selective laboratory methods for obtaining microorganisms from natural samples.

Enzyme

A protein (or in some cases an RNA) catalyst that functions to speed up chemical reactions.

Eukaryotic

Having a membrane-enclosed nucleus and various other membrane-enclosed organelles; cells of Eukarya.

Evolution

A change over time in gene sequence and frequency within a population of organisms, resulting in descent with modification.

Extremophiles

Microorganisms that inhabit environments characterized by extremes of temperature, pH, pressure, or salinity.

Genome

The total complement of genes contained in a cell or virus.

Gram-negative

A bacterial cell with a cell wall containing small amounts of peptidoglycan and an outer membrane.

Gram-positive

A bacterial cell whose cell wall consists chiefly of peptidoglycan; it lacks the outer membrane of gram-negative cells.

Gram stain

A differential staining procedure that stains cells either purple (gram-positive cells) or pink (gram-negative cells).

Growth

In microbiology, an increase in cell number with time.

Gut microbiome

The microbial communities present in the animal gastrointestinal tract.

Horizontal gene transfer

The unidirectional transfer of genes between cells through a process uncoupled from reproduction.

Intercellular communication

Interactions between cells using chemical signals.

Koch's postulates

A set of criteria for proving that a given microorganism causes a given disease.

Macromolecules

A polymer of monomeric units, for example proteins, nucleic acids, polysaccharides, and lipids.

Magnification

The optical enlargement of an image.

Medium (plural, media)

In microbiology, the liquid or solid nutrient mixture(s) used to grow microorganisms.

Metabolism

All biochemical reactions in a cell.

Microbial community

Two or more populations of cells that coexist and interact in a habitat.

Microbial ecology

The study of the interaction of microorganisms with each other and their environment.

Microorganism

An organism that is too small to be seen by the unaided human eye.

Morphology

The physical appearance of a cell as determined by cell shape, for example: rod, coccus, or spirillum.

Motility

The movement of cells by some form of self-propulsion.

Nucleoid

The aggregated mass of DNA that makes up the chromosome(s) of prokaryotic cells.

Nucleus

A membrane-enclosed structure in eukaryotic cells that contains the cell's DNA genome.

Organelle

A bilayer-membrane-enclosed structure such as the mitochondrion, found in eukaryotic cells.

Pathogen

A disease-causing microorganism.

Phylogenetic tree

A diagram that depicts the evolutionary history of an organism; consists of nodes and branches.

Phylogeny

The evolutionary history of organisms.

Plasmid

An extrachromosomal genetic element that is usually not essential to the cell.

Prokaryotic

Lacking a membrane-enclosed nucleus and other organelles; cells of Bacteria or Archaea.

Pure culture

A culture containing a single kind of microorganism.

Resolution

The ability to distinguish two objects as distinct and separate when viewed under the microscope.

Ribosomal RNA (rRNA)

The types of RNA found in the ribosome; some participate actively in protein synthesis.

Ribosome

A cytoplasmic particle composed of ribosomal RNA and protein, whose function is to synthesize proteins.

Spontaneous generation

The hypothesis that living organisms can originate from nonliving matter.

Sterile

Free of all living organisms (cells) and viruses.

Transcription

The synthesis of an RNA molecule complementary to one of the two strands of a double-stranded DNA molecule.

Translation

The synthesis of protein by a ribosome using the genetic information in a messenger RNA as a template.

Cell wall location

Present outside the cytoplasmic membrane.

Cell wall function

Confers structural strength on the cell.

Peptidoglycan

A structural component present in small amounts in gram-negative cell walls and making up the chief component of gram-positive cell walls.

Outer membrane

A membrane component found in the cell wall of gram-negative bacteria that is absent in gram-positive bacteria.

Gram-positive cell wall

A cell wall consisting chiefly of peptidoglycan and lacking the outer membrane found in gram-negative cells.

Gram-negative cell wall

A bacterial cell wall containing small amounts of peptidoglycan and an outer membrane.

Cytoplasmic membrane function

Acts as a semipermeable barrier separating the cell interior (cytoplasm) from the environment.

Fluid portion of the cell

The cytoplasm, which is enclosed by the cytoplasmic membrane.

Organelle membrane structure

A bilayer membrane that encloses structures such as the mitochondrion in eukaryotic cells.

Mitochondrion

An example of a bilayer-membrane-enclosed organelle found in eukaryotic cells.

Nucleus structure

A membrane-enclosed structure in eukaryotic cells containing the cell's DNA genome.

Prokaryotic cell structure

Characterized by lacking a membrane-enclosed nucleus and other organelles; represents cells of Bacteria and Archaea.

Eukaryotic cell structure

Characterized by having a membrane-enclosed nucleus and various other membrane-enclosed organelles; represents cells of Eukarya.

Rigid layer of the cell

The cell wall, which is located outside the cytoplasmic membrane and confers structural strength.

Prokaryotic chromosome

A genetic element, usually circular, carrying genes essential to cellular function in prokaryotic cells.

Prokaryotic DNA mass

The nucleoid, which is the aggregated mass of DNA that makes up the chromosome(s) of prokaryotic cells.

Extrachromosomal genetic element

A plasmid, a genetic element located outside the chromosome that is usually not essential to the cell.

Circular genetic element

The chromosome in prokaryotic cells, which carries genes essential to cellular function.

Complementary RNA molecule

The RNA molecule synthesized during transcription that is complementary to one of the two strands of a double-stranded DNA molecule.

Double-stranded DNA molecule

The genetic molecule from which one strand serves as a template for synthesizing a complementary RNA molecule during transcription.

Messenger RNA (mRNA)

The RNA molecule whose genetic information is used as a template by a ribosome to synthesize protein during translation.

Ribosomal RNA composition

The types of RNA found in the ribosome that, together with protein, compose the ribosome.

Ribosome composition

Composed of ribosomal RNA and protein.

Ribosome location

Located in the cytoplasm as a cytoplasmic particle.

Ribosome function

Functions to synthesize proteins using the genetic information in messenger RNA as a template.

RNA catalyst

An RNA molecule that functions as an enzyme to speed up chemical reactions.

Protein catalyst

An enzyme composed of protein that functions to speed up chemical reactions.

DNA replication product

A new strand of DNA synthesized by copying information from an existing strand of DNA.

Transcription process

The synthesis of an RNA molecule complementary to one of the two strands of a double-stranded DNA molecule.

Translation process

The synthesis of protein by a ribosome using messenger RNA as a template.

Horizontal gene transfer mechanism

The unidirectional transfer of genes between cells via a process uncoupled from reproduction.

Uncoupled gene transfer

Gene transfer occurring independently of reproduction, known as horizontal gene transfer.

Gene sequence change

A change over time in gene sequence within a population of organisms, resulting in descent with modification (evolution).

Gene frequency change

A change over time in gene frequency within a population of organisms, contributing to evolution.

Total complement of genes

The genome, which encompasses all the genes contained within a cell or virus.

Viral genome

The total complement of genes contained within a virus.

Cellular genome

The total complement of genes contained within a living cell.

Essential cellular genes

Genes carried on the chromosome that are essential to cellular function.

Nonessential genetic element

A plasmid, which is an extrachromosomal element that is usually not essential to the cell.

Bacteria

One of the three main evolutionary lineages of cells (Domain), consisting of prokaryotic cells.

Archaea

One of the three main evolutionary lineages of cells (Domain), consisting of prokaryotic cells lacking a membrane-enclosed nucleus.

Eukarya

One of the three main evolutionary lineages of cells (Domain), consisting of eukaryotic cells with membrane-enclosed organelles.

Three main evolutionary lineages

The three cellular domains: the Bacteria, the Archaea, and the Eukarya.

Descent with modification

The outcome of evolution, resulting from changes over time in gene sequence and frequency within a population of organisms.

Nodes

Structural branch points within a phylogenetic tree that depict the evolutionary history of organisms.

Branches

Lineages on a phylogenetic tree that connect nodes and depict evolutionary relationships.

Phylogenetic tree structure

A diagram composed of nodes and branches that depicts an organism's evolutionary history.

Organismal evolutionary history

Phylogeny, which represents the evolutionary history of organisms.

Extremophile habitats

Environments characterized by extremes of temperature, pH, pressure, or salinity.