Viruses, Prokaryotes, Ecological Roles, and Protists Vocabulary

Comprehensive vocabulary flashcards covering viruses, prokaryotes, prokaryotic ecological roles, and protists based on the provided lecture sources.

Virus

A biological entity consisting of genetic information (DNA or RNA) enclosed within a protein coat, straddling the boundary between chemistry and biology.

Capsid

The protective protein coat surrounding the genetic material of a virus.

Viral Envelope

An outer layer surrounding some viruses that is derived directly from the host cell's membrane.

Bacteriophage

A complex virus that specifically infects bacterial cells.

Regressive Hypothesis

The hypothesis suggesting that viruses evolved from once-larger, parasitic cells that lost their complex cellular machinery over time.

Escaped Genes Hypothesis

The hypothesis proposing that viruses originated from mobile cellular genetic elements, such as transposons or plasmids, that left host genomes.

Coevolution Hypothesis

The hypothesis positing that viruses evolved alongside early complex cells and have always been dependent on cellular life.

Host Range

The specific scope of organism species or cell types that a particular virus can infect.

Reservoir

The natural environment or host organism site where a virus continually exists and persists in nature when not actively causing an outbreak.

Prophage

Bacteriophage DNA that has been inserted and integrated into the host bacterium's DNA during penetration.

Lytic Infection

A viral infection in bacteria where newly replicated viruses cause the host cell to burst and die immediately.

Lysogenic Infection

A viral infection where viral genetic material integrates as a prophage and replicates alongside the host cell without killing it immediately.

Enterobacteria phage lambda

A specific bacteriophage widely studied as a model virus in research to understand viral mechanisms.

Latent Infection

A persistent viral infection in which viral genetic material is integrated into the host genome but remains unexpressed for an extended period.

Retrovirus

An RNA virus that utilizes reverse transcriptase to convert its RNA genome into DNA prior to integration into the host genome.

Viroids

Infectious agents consisting of short, free-floating coils of RNA without a protein coat that infect plant cells and do not encode proteins.

Prions

Infectious misfolded proteins that cause surrounding normal proteins to adopt the same malformed, disease-causing conformation.

Prokaryotes

Single-celled organisms that lack a membrane-enclosed nucleus and membrane-bound organelles.

Domain Archaea

A domain of prokaryotes characterized by nonfatty acid membrane lipids and cell walls lacking peptidoglycan, evolutionary closer to Eukarya than Bacteria.

Domain Bacteria

A domain of prokaryotes characterized by fatty acid membrane lipids and cell walls composed primarily of peptidoglycan.

Nucleoid

The non-membrane-bound cytoplasmic region in a prokaryote containing its circular DNA chromosome.

Plasmids

Small, circular extrachromosomal DNA molecules in prokaryotes that carry additional non-essential genes.

Peptidoglycan

A complex polymer forming the primary structural component of bacterial cell walls.

Gram Stain

A differential staining technique using two dyes to categorize bacteria into Gram-positive or Gram-negative based on cell wall architecture.

Gram-Positive Bacteria

Bacteria possessing a thick layer of peptidoglycan in their cell wall, retaining stain to appear dark purple.

Gram-Negative Bacteria

Bacteria having an inner and outer membrane with a thin peptidoglycan layer in between, staining light pink.

Penicillin

An antibiotic discovered in $1928$ that disrupts cell wall synthesis by inhibiting peptidoglycan cross-linkages, primarily targeting Gram-positive bacteria.

Coccus

A spherical-shaped bacterial cell.

Staphylococcus

Spherical bacteria (cocci) arranged in grape-like clusters.

Streptococcus

Spherical bacteria (cocci) arranged in linear chains.

Bacillus

A rod-shaped bacterial cell.

Streptobacillus

Rod-shaped bacteria (bacilli) arranged in end-to-end chains.

Spirillium

A spiral or corkscrew-shaped bacterial cell.

Glycocalyx

An outer layer of proteins and polysaccharides surrounding the cell wall of some prokaryotes, aiding in biofilm formation.

Endospore

A dormant, resistant structure generated by certain Gram-positive bacteria to enclose the nucleus and cytoplasm during unfavorable environmental conditions.

Pili

Short protein projections on prokaryotic cell surfaces that help cells adhere to objects.

Taxis

Directional motility of a prokaryote toward or away from a stimulus.

Autotrophs

Organisms that assemble their own organic molecules directly from inorganic sources like $\text{CO}_2$.

Phototrophs

Autotrophic organisms that derive energy from sunlight.

Chemotrophs

Autotrophic organisms that oxidize inorganic or organic chemicals for energy.

Heterotrophs

Organisms that obtain carbon by consuming organic molecules synthesized by other organisms.

Obligate Aerobes

Prokaryotes that require oxygen ($\text{O}_2$) for cellular respiration and survival.

Obligate Anaerobes

Prokaryotes for which oxygen ($\text{O}_2$) is toxic.

Facultative Anaerobes

Prokaryotes capable of living and carrying out metabolism with or without oxygen ($\text{O}_2$).

Binary Fission

An asexual reproduction process in prokaryotes involving cell division into two identical cells following growth and DNA replication.

Horizontal Gene Transfer

Process by which a cell receives genetic material from another cell that is not its direct ancestor.

Transformation

A form of horizontal gene transfer where a cell absorbs stray extracellular DNA fragments or plasmids from its environment.

Transduction

A form of horizontal gene transfer where a virus transfers host DNA from a previous host cell to a new cell.

Conjugation

A form of horizontal gene transfer where one cell receives DNA via direct contact with another cell through a sex pilus.

Sex Pilus

A specialized appendage through which DNA passes from a donor prokaryotic cell to a recipient cell during conjugation.

Nutrient Cycling

The movement and exchange of organic and inorganic matter back into the production of biological matter.

Cyanobacteria

Photosynthetic prokaryotes (blue-green algae) possessing internal membranes, capable of fixing atmospheric carbon dioxide ($\text{CO}_2$).

Cellulase

A bacterial enzyme used to break cellulose down into digestible glucose monomers.

Diazotrophs

Prokaryotes capable of fixing atmospheric nitrogen gas ($\text{N}_2$) into ammonia ($\text{NH}_3$).

Symbiosis

An intimate physical relationship between two different species of organisms.

Mutualism

A symbiotic relationship in which both participating organisms derive biological benefits.

Microbiome

The collection of microorganisms living in a particular environment or host body.

Ruminococcus flavefaciens

A mutualistic gut bacterium in ruminants that produces cellulase to break down plant cellulose.

Rhizobia

Nitrogen-fixing bacteria living in specialized root nodules of plants in the family Fabaceae.

Pathogen

A bacterium, virus, or other microorganism that causes disease.

Opportunistic Infection

An infection caused by naturally present or weak microbes when a host's immune system or tissue barrier is compromised.

Epidemiology

The study of the distribution and determinants of disease in populations.

Eutrophication

An excessive richness of nutrients in a body of water that triggers rapid growth of cyanobacteria or algae.

Hypoxic Conditions

Low-oxygen conditions in water resulting from nutrient depletion and decomposition of algal blooms.

Cyanotoxins

Toxic chemical compounds produced and released by cyanobacteria during dense blooms.

Protist

A eukaryotic organism that is designated as Protista because it does not fall into the kingdoms Plantae, Animalia, or Fungi.

Algae

An informal term broadly referring to plant-like photosynthetic eukaryotic protists.

Euglenoids

Photosynthetic protists with elongated cells and typically one long flagellum, capable of becoming heterotrophic in low-light conditions.

Dinoflagellates

Unicellular protists characterized by two flagella and cell walls composed of overlapping cellulose plates.

Red Tide

An algal bloom caused by dense populations of dinoflagellates, often releasing harmful toxins.

Diatoms

Unicellular photosynthetic algae enclosed within a two-part silica wall called a frustule.

Frustule

The rigid, two-part silica cell wall surrounding a diatom cell.

Centric Diatoms

Diatoms exhibiting radial symmetry in their silica frustules.

Pennate Diatoms

Diatoms exhibiting bilateral symmetry in their silica frustules.

Brown Algae

The largest and structurally most complex multicellular photosynthetic protists.

Red Algae

Multicellular photosynthetic protists adapted with specialized pigments to inhabit deep-water habitats.

Green Algae

Photosynthetic protists most closely related to land plants in photosynthetic pathways and reproduction.

Protozoans

Unicellular heterotrophic protists categorized by locomotion into flagellates, amoeboids, ciliates, and apicomplexans.

Flagellates

Unicellular protozoans that propel themselves using one or more whip-like flagella.

Giardia lamblia

A parasitic flagellate protozoan found in untreated water that causes intestinal giardiasis upon cyst consumption.

Trypanosomes

Flagellate protists transmitted by the tsetse fly that cause African Sleeping Sickness.

Dinoflagellate Luciferase

An enzyme in marine dinoflagellates that catalyzes light emission using luciferin substrate to generate bioluminescence.

Zooxanthellae

Symbiotic dinoflagellates residing within host tissues of corals and other marine organisms.

Coral Bleaching

The loss or expulsion of symbiotic zooxanthellae from stressed corals, causing them to lose coloration.

Amoeboids

Heterotrophic protozoans with flexible body shapes that move via pseudopodia and feed by phagocytosis.

Pseudopodia

Temporary cytoplasmic extensions ('false feet') used by amoeboid cells for locomotion and feeding.

Foraminiferans

Marine amoeboids characterized by intricate calcium carbonate shells known as tests.

Radiolarians

Ancient marine protozoans with rigid silica tests containing tiny holes through which pseudopodia extend.

Ciliates

Complex protozoans characterized by abundant hair-like cilia, contractile vacuoles, and micronuclei exchanged during conjugation.

Apicomplexans

Nonmotile, spore-forming internal animal parasites possessing complex life cycles.

Plasmodium

The genus of apicomplexan parasites responsible for causing malaria infections.

Slime Molds

Heterotrophic protist associations of numerous individual cells that resemble fungi.

Plasmodium Slime Mold

A type of slime mold existing as a multinucleate mass of cytoplasm encased within a single cell membrane.

Cellular Slime Mold

A type of slime mold whose individual cells aggregate while maintaining their distinct cell membranes throughout the life cycle.