Viruses, Bacteria, and Archaea Flashcards

Vocabulary flashcards covering the characteristics, reproduction, and genetics of viruses, bacteria, and archaea based on lecture notes.

Virus

An infectious particle composed of a small chromosome (DNA or RNA) surrounded by a protein coat called a capsid.

Capsid

The protein coat that surrounds the viral chromosome.

Envelope

A membrane that surrounds the capsid in some specific types of viruses.

Host range

The different types of cells a virus can infect, limited by the "lock and key" specificity of viral attachment to membrane proteins.

Lytic cycle

A viral reproductive pathway where the host cell actively reproduces the virus until the cell bursts.

Retroviruses

RNA viruses that provide an enzyme called reverse transcriptase to make complementary DNA from their RNA chromosome.

Reverse transcriptase

An enzyme provided by retroviruses that creates a complementary DNA (cDNA) from an RNA template.

Lysogenic cycle (latency)

A reproductive pathway where the viral chromosome inserts into the host cell chromosome and enters a period of little or no activity.

Provirus (Prophage)

The viral DNA once it has been inserted into the host cell's chromosome during the lysogenic cycle.

Prokaryotes

Unicellular organisms, such as bacteria and archaea, that have a single circular chromosome and lack a nucleus surrounding their DNA.

Binary fission

A method of rapid asexual reproduction where cell division occurs immediately after DNA replication.

Archaea

Prokaryotes with cell walls and membranes made of different molecules than bacteria, often living in extreme environments.

Thermophiles

Archaea that are adapted to live at high temperatures.

Acidophiles

Archaea that thrive in environments with an acidic $pH$.

Halophiles

Archaea that live in high salt environments.

Methanogens

Archaea that live in anaerobic environments and produce methane gas by decomposing plant and animal wastes.

Bacteria

Prokaryotes found in almost all environments with cell walls composed of peptidoglycan.

Peptidoglycan

A material found in bacterial cell walls consisting of chains of sugars cross-linked by short polypeptides.

Gram positive bacteria

Bacteria with a thick peptidoglycan cell wall that stains purple with Grams stain.

Gram negative bacteria

Bacteria with a thin peptidoglycan cell wall that stains pink with Grams stain.

Cyanobacteria

A type of beneficial bacteria capable of performing photosynthesis.

$N_2$ fixing bacteria

Bacteria that convert nitrogen gas from the air into a form plants can use to produce proteins and DNA.

Pathogenic

A term describing organisms, such as certain bacteria, that cause disease.

Plasmids

Small circular pieces of DNA found in bacteria that contain fewer than $100$ genes.

Transformation

A method of gene transfer where a bacteria takes in naked foreign DNA and incorporates it into its chromosome.

Transduction

A gene transfer method where a bacteriophage virus accidentally packages and transfers bacterial DNA from one cell to another.

Conjugation

The transfer of DNA between bacteria through a temporary structure called a sex pilus.

Sex pilus

A temporary structure that links two bacterial cells and establishes a bridge between their cytoplasms for DNA transfer.

F factor

A group of genes that enable a bacteria to form a sex pilus; its presence designates a cell as $F^+$ or hfr.

Operon

A region of the bacterial chromosome containing several genes (usually for one metabolic pathway), a promoter, and an operator.

Operator

A sequence within the promoter of an operon where a repressor protein binds to shut down transcription.

Repressor protein

A protein that stops transcription by binding to the operator and blocking RNA Polymerase from the promoter.

Co-repressor

A small molecule, such as the amino acid Tryptophan, that allosterically activates a repressor protein.

Inducer

A small molecule, such as the disaccharide Lactose, that allosterically inhibits a repressor protein.

Activator protein

A protein that increases transcription by helping RNA Polymerase attach to the promoter.

CAP protein

An activator protein of the Lac operon that is activated by cAMP.

cAMP

An allosteric regulator that activates the CAP protein, present only when the bacterial cell is starving for glucose.