Eukaryotic Microbes, Viruses, Phages, and Prions

Comprehensive vocabulary flashcards covering the characteristics, classification, life cycles, and clinical significance of eukaryotic microbes, viruses, phages, and subviral particles.

Holozoic nutrition

A heterotrophic mode of nutrition characterized by the intake and internal processing of solid or liquid organic particles, typically via phagocytosis.

Saprozoic nutrition

A heterotrophic nutritional mode involving the absorption of dissolved, small organic molecules from dead and decaying matter.

Cytostome

A specialized protozoan cell structure that functions as a cellular mouth dedicated to phagocytic food ingestion.

Cytoproct

A specialized cellular structure in protozoans functioning as an anal pore for the exocytic excretion of metabolic waste products.

Pellicle

A proteinaceous supporting layer situated directly beneath the plasma membrane in certain protozoans that provides cellular rigidity.

Schizogony

An asexual multiple fission process in protozoans where the nucleus divides several times before the cytoplasm segments into multiple daughter cells (merozoites).

Fornicata

A phylum within Excavata containing anaerobic, flagellated parasites (such as Giardia lamblia) that lack mitochondria and Golgi apparatus.

Giardia lamblia

A flagellated, waterborne Fornicata diplomonad parasite lacking mitochondria that produces cysts contaminating water supplies and causes diarrheal disease.

Trichomonas vaginalis

A sexually transmitted parabasalid protozoan characterized by an undulating membrane and flagella that lacks mitochondria and cyst forms, associated with premature labor in pregnancy.

Kinetoplast

A dense, organized granule of mitochondrial DNA located inside the single elongated mitochondrion of kinetoplastid protozoans.

Tsetse fly

The biological insect vector that transmits Trypanosoma brucei, the causative protozoan agent of African sleeping sickness, via its bite.

Kissing bug

A blood-feeding triatomine insect that bites the human face during nocturnal sleep, serving as the biological vector for Trypanosoma cruzi (Chagas disease).

Leishmania

A genus of flagellated kinetoplastids transmitted by sand flies that causes severe, disfiguring cutaneous and visceral diseases in humans.

Apical complex

A specialized cytoskeletal and secretory organelle arrangement at the anterior tip of apicomplexans that facilitates entry and invasion into host cells.

Apicoplast

A non-photosynthetic, relic chloroplast-derived organelle found inside obligate intracellular apicomplexan parasites.

Cryptosporidium parvum

An apicomplexan pathogen of humans and cattle that causes severe epidemic diarrhea through cysts that contaminate public water supplies.

Toxoplasma gondii

An apicomplexan parasite with a feline primary host that can cause severe toxoplasmosis in immunocompromised individuals and congenital birth defects when contracted by pregnant women.

Plasmodium falciparum

The most lethal mosquito-borne apicomplexan parasite causing human malaria, characterized by cyclical invasion and asexual replication in erythrocytes.

Ciliate conjugation

A sexual process in ciliates during which two cells physically adhere and reciprocally exchange haploid micronuclei to generate genetic diversity.

Phytophthora

A diploid oomycete (water mold) with cellulose cell walls that triggered the historic Irish potato famine, leading to $1\,\text{million}$ deaths and $1\,\text{million}$ emigrants.

Naegleria fowleri

A free-living amoebozoan known colloquially as the 'brain-eating amoeba' that causes fatal primary amebic meningoencephalitis (PAM).

Sclerotium

A hardened, resistant dormant resting body formed by the plasmodial slime mold Physarum polycephalum upon sensing desiccating environmental conditions.

Dictyostelium discoideum

A cellular slime mold whose independent haploid amoebae aggregate into a coordinated motile slug and fruiting body during nutrient scarcity.

Ascaris lumbricoides

A large parasitic roundworm (nematode) measuring $15\text{ to }30\,\text{cm}$ (up to $1\,\text{m}$) whose larvae hatch in the gut, migrate through the lungs, and are swallowed to mature in the small intestine.

Schistosoma mansoni

A parasitic trematode (flatworm) whose cercariae emerge from freshwater snails and penetrate human skin, causing schistosomiasis (bilharzia or snail fever).

Scolex

The specialized head-like anterior attachment organ of a tapeworm (Cestoda) bearing suckers or hooks used to anchor into the host intestinal mucosa.

Ergosterol

The fundamental sterol lipid in fungal plasma membranes that replaces animal cholesterol and serves as the primary molecular target of antifungal drugs.

Histoplasma capsulatum

A thermally dimorphic fungus that grows as a sporulating filamentous mold in soil with bird/bat droppings and transitions to a pathogenic yeast in human lung tissue.

Aflatoxin

A potent carcinogenic toxin synthesized by the ascomycete molds Aspergillus flavus and Aspergillus parasiticus that contaminates agricultural staples such as peanuts, millet, and corn.

Lichen growth forms

The three standard morphological forms of composite lichen thalli: crustose (crust-like adherence), foliose (flattened, leaf-like lobes), and fruticose (bushy, pendulous branching).

Microsporidia

Unicellular, obligate intracellular fungal parasites that lack traditional mitochondria and use a coiled polar tubule to inject infectious sporoplasm into host cells.

Theca

A rigid, protective cellular armor consisting of cellulose plates found lining the outer surface of certain photosynthetic or heterotrophic dinoflagellates.

Chamberland filter

An unglazed porcelain filter invented by Charles Chamberland with pores smaller than $100\,\text{nm}$ capable of retaining bacterial cells while letting viruses pass.

Dmitri Ivanovski

The Russian researcher who in 1892 demonstrated that the infectious agent of tobacco mosaic disease passed through porcelain filters that retained bacteria.

Martinus Beijerinck

The Dutch microbiologist who in 1899 coined the term 'virus' (Latin for 'poisonous secretion') to define the filter-passing infectious agent of tobacco mosaic disease.

Edward Jenner

The English doctor who in 1796 demonstrated that inoculating James Phipps with cowpox pustule matter from Sarah Nelms protected him from smallpox, inaugurating vaccination.

rVSV-ZEBOV

A replication-competent recombinant vesicular stomatitis virus vaccine engineered by Canadian scientists to express a glycoprotein from Zaire ebolavirus.

Spanish Flu

The devastating pandemic of $1918\text{--}1920$ caused by an H1N1 influenza A virus that infected $500\,\text{million}$ individuals and caused an estimated $50\,\text{million}$ deaths.

Zoonosis

An infectious disease caused by a pathogen that transfers naturally from a non-human animal reservoir species directly or indirectly to humans.

Biological vector

An arthropod vector that harbors an infectious virus internally, supports its replication or development, and transmits it to a host via biting.

Mechanical vector

An animal vector that transports a pathogen on the exterior of its physical body, depositing it onto new hosts or surfaces purely by physical contact.

Capsomere

An individual, interlocking protein subunit that self-assembles to form the protective protein capsid of a virion.

Viral capsid morphologies

The three classical structural forms assumed by viral capsids: helical (rod-shaped/cylindrical), icosahedral (multifaceted 20-sided polygon), and complex (atypical or combined architectures).

Hemagglutinin (H)

An envelope spike glycoprotein on influenza viruses that binds sialic acid residues on host epithelial cells and mediates red blood cell agglutination.

Neuraminidase (N)

An enzymatic glycoprotein spike on influenza envelopes that cleaves host receptor sialic acid to liberate budding progeny virions from the cell surface.

ICTV taxonomy

The formal viral classification framework established by the International Committee on Taxonomy of Viruses, featuring family names ending in -viridae and genera ending in -virus.

+ssRNA virus

A positive-sense single-stranded RNA virus whose genomic RNA functions directly as messenger RNA capable of immediate translation by host ribosomes.

-ssRNA virus

A negative-sense single-stranded RNA virus whose genome cannot be translated directly and must first be transcribed into complementary +ssRNA by viral RdRp.

RNA-dependent RNA polymerase (RdRp)

A viral enzyme that synthesizes a complementary RNA strand from an RNA template, critical for replicating and transcribing RNA viral genomes.

Reverse transcriptase

A specialized viral DNA polymerase carried by retroviruses that transcribes single-stranded viral RNA into double-stranded DNA for host genome integration.

Prophage

The latent, integrated bacteriophage DNA genome that resides harmlessly inside a bacterial host chromosome during the lysogenic cycle.

Specialized transduction

The horizontal gene transfer process where precise host bacterial genes flanking a prophage excision site are packaged and transferred during lysogenic induction.

Tissue tropism

The specific affinity of a virus for infecting particular cell types or organ tissues determined by surface receptor compatibility.

Latent infection

A persistent viral condition wherein the viral genome remains dormant inside the host without active replication until specific triggers induce reactivation (e.g., HSV or Varicella-zoster).

Potato spindle tuber viroid (PSTV)

A subviral plant pathogen composed entirely of a naked circular single-stranded RNA molecule that causes elongation, cracking, and gnarling of potato tubers.

Virusoid

A small circular non-self-replicating ssRNA molecule ($>220\,\text{nt}$) devoid of protein that strictly requires coinfection with a specific helper virus to achieve replication.

Prion (PrPSc)

A proteinaceous infectious particle lacking any nucleic acid genome that propagates by inducing the conformational misfolding of host cellular PrPC into pathogenic amyloid aggregates.

Eclipse phase

The initial interval in a viral one-step growth curve following inoculation during which virions penetrate host cells and no infectious virus can be detected in the medium.

Continuous cell line

An immortalized in vitro culture of transformed or neoplastic animal cells (such as HeLa cells) that can proliferate indefinitely without contact inhibition.

Cytopathic effects (CPEs)

Observable morphological and structural abnormalities in cultured host cells caused by viral infection, including cell detachment, syncytia formation, and inclusion bodies.