Common Terms to Know: Prokaryotes and Viruses

These flashcards cover key vocabulary and concepts related to the phylogeny of prokaryotes and the characteristics of viruses.

Phylogeny

The evolutionary history and relationships among species or groups of organisms.

Prokaryotes

Single-celled organisms that lack a membrane-bound nucleus; includes Bacteria and Archaea.

Autotroph

An organism that produces its own food from inorganic substances; can be photoautotrophs or chemoautotrophs.

Heterotroph

An organism that obtains its food by consuming other organic matter.

Obligate Anaerobes

Organisms that cannot survive in the presence of oxygen and must use fermentation for energy.

Facultative Anaerobes

Organisms that can use oxygen when present but can also grow without it, through fermentation.

Endospore

A resistant structure formed by certain bacteria to survive harsh conditions.

Exotoxins

Toxic substances secreted by bacteria that can harm host cells.

Antibiotic Resistance

The ability of bacteria to resist the effects of an antibiotic.

Gram-positive Bacteria

Bacteria that have a thick peptidoglycan layer in their cell wall and retain the crystal violet stain.

Gram-negative Bacteria

Bacteria that have a thin peptidoglycan layer and are decolorized by alcohol, not retaining the crystal violet stain.

Lytic Cycle

A viral reproductive cycle where the virus enters a host cell, replicates, and ultimately causes the cell to burst.

Lysogenic Cycle

A viral reproductive cycle in which the virus integrates its DNA into the host chromosome and replicates with it.

Reverse Transcriptase

An enzyme used by retroviruses to convert their RNA into DNA.

Viral Envelope

A membrane stolen from the host cell that surrounds some viruses, containing glycoproteins.

Zoonotic Virus

A virus that is transmitted from animals to humans.

Viroids

Small circular RNA molecules that can cause diseases in plants.

Mutation

A change in the genetic sequence of an organism.

Phage

A virus that infects bacteria, also known as a bacteriophage.

Viruses

Tiny infectious agents that carry genetic material and rely on host cells to replicate.

Capsid

A protein coat made of capsomeres that encloses the viral genome.

Capsomeres

The protein subunits that assemble spontaneously to form the capsid.

Viral envelope

A membranous accessory structure derived from the host cells’s membrane, often found in animal viruses.

Host range

The specific collection of host cells a virus can infect, determined by viral surface proteins like glycoproteins.

Bacteriophage

A virus that infect bacteria, often with a complex capsid capable of injecting its genome into the host.

Lytic cycle

A viral replication cycle that results in the destruction (lysis) of the host cell and release a new viruses.

Virulent phage

A bacteriophage that replicates only via the lytic cycle.

Restriction enzymes

Bacterial enzymes that degrade foreign viral DNA as a defense mechanism.

Lysogenic cycle

A viral replication cycle where the viral genome integrates into the host genome as a prophage and replicates without killing the host.

Prophage

The viral DNA integrated into the bacterial chromosome during the lysogenic cycle.

Temperate phage

A phage capable of both lytic and lysogenic cycles.

Endocytosis

A process by which animus viruses enter host cells by begging engulfed through the cell membrane.

Reverse transcriptase

An enzyme used by retroviruses to transcribe RNA into DNA for integration into the host genome.

Provirus

Viral DNA integrated into the host genome in animal cells, produced by retroviruses using reverse transcriptase.

Retrovirus

An RNA virus that uses reverse transcription to insert a DNA copy of its genome into the host’s DNA.

Single-stranded RNA virus

Viruses with RNA genomes that can be either positive-sense (coding strand) or negative-sene (template stran).

Positive-sense RNA virus

A single-stranded RNA virus whose genome can be directly translated into viral proteins.

Negative-sense RNA virus

A single-stranded RNA virus whose genome is complementary to mRNA and required viral RNA polymerase to produce mRNA.

Viroids

Small, circular single-stranded RNA pathogens that infect plants and do not encode proteins.

Prions

Infectious proteins that cause misfolding of normal proteins, leading to neurodegenerative diseases.

Glycoproteins

Proteins with carbohydrate chains on the viral envelope that help viruses recognize and bind to host cells.

Prokaryotes

Prokaryotic cells

Cells without a nuclear or membrane-bound organelles, found in domain Bacteria and Archaea.

Nucleoid

The region in prokaryotic cells where circular DNA is located, not enclosed by a membrane.

Binary fission

A simple form of cell division used by prokaryotes to reproduce asexually.

Ribosomes

Cellular structures responsible for protein synthesis; prokaryotic ribosomes are 70S

Peptidoglycan

A molecule forming the cell wall of bacteria, absent in archaea.

Extremophiles

Organisms, especially some archaea, that thrive in extreme environments such as high temperatures, salinity, or pressure.

Domain of life

Three major groups of life: Bacteria, Archaea, Eukarya

Circular DNA

The form of DNA found in prokaryotes, typically located in the nucleoid region.

Unicellular

Organisms composed of a single cell, typical of prokaryotes.

Prokaryotic cell structure

Unique components that enable their survival and function.

Cell wall

A semi-rigid structural layer located outside the cell membrane that provides protection and maintains cell shape, primarily composed of peptidoglycan in bacteria.

peptidoglycan

A rigid mesh-like polysaccharide and protein mixture that forms the main component of bacterial cell walls, providing structural support and rigidit

Cells envelope

The collective term for all layers surrounding a bacterial cell, including the cell membrane, cell wall, and other membranes or capsule if present.

Gram-negative bacteria

Bacteria with a thin Peptidoglycan layer and an additional complex outer membrane, which do not retain the Gram Stan.

Gram-positive bacteria

Bacteria with a thick Peptidoglycan layer in their cell walls that absorb the Gram stain and appear purple under a microscope.

Outer membrane

An extra membrane found in gram-negative bacteria outside the Peptidoglycan layer, contributing to their structural complexity and protection.

Glycocalyx

A sticky, gel-like complex polysaccharide layer surrounding many bacterial cells that aids in adhesion, protection from dehydration, and nutrient collection.

Capsule

Highly organized, dense form of glycocalyx tightly anchored to the bacterial cells surface, providing protection and aiding in immune evasion.

Slime layer

An unorganized, loosely attached form of glycocalyx that can be easily removed and helps bacteria adhered to surfaces.

Biofilms

Communities of microbes living together within an extracellular polymeric substance, often formed with the help of glycocalyx and fimbriae.

Pili

Long filamentous protein structures on bacterial surfaces that function in motility and DNA transfer between cells.

Fimbriae

Shorter protein filaments than Pili that help bacterial cells adhered to each other and to surfaces, playing a key role in biofilm formation.

Endospores

Dormant, highly resistant bacterial cells formed by some gram-positive bacteria to survive extreme conditions such as heat, chemicals, and nutrients depletion.

Vegetative cells

A normal, metabolically active bacteria cell capable of growth and reproduction, as opposed to a dormant endospore.

Sporulation

The process by which a vegetative bacterial cell forms an endospore in response to unfavorable conditions.

Germination

The process by which an endospore reverts back to a vegetative cell when favorable conditions return.

Prokaryotic Motility

Movement of prokaryotic cells, such as bacteria, primarily driven by structures like flagella that enable navigation toward favorable environments.

Flagella

Long filamentous surface proteins that propel prokaryotic cells through their environment, enabling motility.

Flagellum

The singular form of flagella: a single whip-like structure used for cell movement.

Filament

The primary component of a prokaryotic flagellum made of globular protein flagellin, forming the long, helical structure.

Hooks

A flexible, curbed protein that connects the filament to the basal body, allowing the flagellum to rotate and propel the cell.

Basal body

The motor component of the flagellum embedded in the cell envelope, consisting of a rod and protein rings that anchor the flagellum and generate rotation .

Proton motive force

The electrochemical gradient of protons across the membrane that provides energy for flagella rotation and cell motility.

Chemotaxis

The directed movement of a motile cell toward a chemoattractant or away from a chemorepellant.

Chemoattractant

A chemical substance that attracts motile cells, causing positive chemotaxis.

Chemorepellant

A chemical that repels motile cells, causing negative chemotaxis.

Positive chemotaxis

Move of a cell toward a chemoattractant.

Negative chemotaxis

Movement of a cell away from chemorepellant.

Phototaxis

A specific type of chemotaxis where cells move toward or away from light stimuli.

Tuft

A group of multiple flagella on the surface of a single prokaryotic cell.

Runs and tumbles

The alternating movement pattern of motile cells, where runs are straight swims and tumbles are random reorientations, resulting in a non-linear path.

Prokaryotic reproduction

Bacteria replicate and exchange genetic material, inducing binary fission. And horizontal gene transfer.

Plasmid

A small, circular double-stranded DNA molecule that replicates independently of the bacterial chromosome and often carries genes that provide advantages such as antibiotic resistance.

Binary fission

A form of asexual reproduction in prokaryotes where a single parental cell divides into two genetically identical daughter cells.

Horizontal gene transfer

The movement of genetical material between organisms that are not parent and offspring, increasing generic diversity in prokaryotes.

Transformation

A mechanism of horizontal gene transfer where a component bacterial cell uptakes free or naked DNA from its environment.

Competente cell

A bacterial cell in a physiological state that allows it to uptake external DNA during transformation.

Transduction

Horizontal gene transfer mediated by bacteriophages, where bacterial DNA is accidentally packaged into a phage and transferred to another cell.

Bacteriophages:

A virus that infects bacteria and can mediate gene transfer during transduction.

Transduction particle

A defective bacteriophage carrying bacterial DNA instead of viral DNA, capable of transferring bacterial genes to another cell.

Conjugation

Direct transfer of DNA between two bacterial cells through cell-to-cell contact, often involving a sex pilus.

Sex pills (conjugation pilus)

A protein structure that connects donor and recipient bacterial cells to facilitate DNA transfer during conjugation.

Conjugation plasmid

A plasmid capable of directing its own transfer from a donor to a recipient cell via conjugation.

F plasmid (fertility plasmid)

A well-studied conjugation plasmid in E. Coli that enables the formation of the F pilus and transfer of genetic material.

F+ cell

A bacterial cell containing the entire F plasmid, capable of donating it during conjugation and forming an F Pilus.

F- cell

A bacterial cell lacking the entire F plasmid, serving as a recipient during conjugation and unable to form an F Pilus.

HFR cell

A bacterial cell with the F plasmid integrated into its chromosome, capable of transferring chromosomal genes during conjugation.

Origin of replication

A specific DNA sequence on a plasmid where replication begins during conjugation.