Chapters 19/27 Vocabulary

F factor

In bacteria, the DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient.

endotoxin

A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.

vaccine

A harmless variant or derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen.

viral envelope

A membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome.

Viroid

A plant pathogen consisting of a molecule of naked, circular RNA a few hundred nucleotides long.

Methanogen

An organism that produces methane as a waste product of the way it obtains energy.

virulent phage

A phage that replicates only by a lytic cycle.

virus

An infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some, a membranous envelope.

temperate phage

A phage that is capable of replicating by either a lytic or lysogenic cycle.

reverse transcriptase

An enzyme encoded by certain viruses (retrovi- ruses) that uses RNA as a template for DNA synthesis.

transformation

A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, results in horizontal gene transfer.

Transduction

A process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species, results in horizontal gene transfer.

Taxis

An oriented movement toward or away from a stimulus.

Prophage

A phage genome that has been inserted into a specific site on a bacterial chromosome.

Retrovirus

An RNA virus that replicates by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer- causing viruses.

restriction enzyme

An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium (such as phage genomes). The enzyme cuts at specific nucleotide sequences (restriction sites).

provirus

A viral genome that is permanently inserted into a host genome.

R plasmid

A bacterial plasmid carrying genes that confer resistance to certain antibiotics.

pilus (plural, pili)

In bacteria, a structure that links one cell to another at the start of conjugation

prion

An infectious agent that is a misfolded version of a normal cellular protein.

Plasmid

A small, circular, double- stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome

pathogen

An organism or virus that causes disease.

peptidoglycan

A type of polymer in bacterial cell walls consisting of modified sugars cross-linked by short polypeptides.

nitrogen fixation

The conversion of atmospheric nitrogen (N2) to ammonia (NH3). Biological nitrogen fixation is carried out by certain prokaryotes, some of which have mutualistic relationships with plants.

obligate aerobe

An organism that requires oxygen for cellular respiration and cannot live without it.

obligate anaerobe

An organism that carries out only fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.

pandemic

A global epidemic. HAHA You'd better know this one!

lysogenic cycle

A type of phage replicative cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage, is replicated along with the chromosome, and does not kill the host.

lytic cycle

A type of phage replicative cycle resulting in the release of new phages by lysis (and death) of the host cell.

fimbria (plural, fimbriae)

A short, hairlike appendage of a prokaryotic cell that helps it adhere to the substrate or to other cells.

host

The larger participant in a symbiotic relationship, often providing a home and food source for the smaller symbiont.

host range

The limited number of species whose cells can be infected by a particular virus.

Heterocyst (also called heterocyte)

A specialized cell that engages in nitrogen fixation in some filamentous cyanobacteria

Gram stain

A staining method that distinguishes between two different kinds of bacterial cell walls; may be used to help determine medical response to an infection.

gram-negative

Describing the group of bacteria that have a cell wall that is structurally more complex and contains less peptidoglycan than other bacteria.

gram-positive

Describing the group of bacteria that have a cell wall that is structurally less complex and contains more peptidoglycan than the cell wall of other bacteria.

F plasmid

The plasmid form of the F factor.

epidemic

A widespread outbreak of a disease

exotoxin

A toxic protein that is secreted by a prokaryote or other pathogen and that produces specific symptoms, even if the pathogen is no longer present.

extreme halophile

An organism that lives in a highly saline environment, such as the Great Salt Lake or the Dead Sea.

extreme thermophile

An organism that thrives in hot environments (often 60-80°C or hotter).

extremophile

An organism that lives in environmental conditions so extreme that few other species can survive there.

Conjugation

In prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. When the two cells are members of different species, conjugation results in horizontal gene transfer.

endospore

A thick-coated, resistant cell produced by some bacterial cells when they are exposed to harsh conditions.

Bacteriophage

A virus that infects bacteria

biofilm

A surface-coating colony of one or more species of prokaryotes that engage in metabolic cooperation.

bioremediation

The use of organisms to detoxify and restore polluted and degraded ecosystems

capsid

The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.

capsule

In many prokaryotes, a dense and well-defined layer of polysaccharide or protein that surrounds the cell wall and is sticky, protecting the cell and enabling it to adhere to substrates or other cells.