Microbiology Quiz 3: Viruses, Bacteria, and Immunity

Comprehensive vocabulary flashcards covering viral biology, structural classifications, polymerases, defense and phage mechanisms, transduction, innate vs. adaptive immune branches, and viral mutation mechanisms.

Virus

A non-living, infectious package that can evolve and multiply only inside a host cell, cannot metabolize, cannot respond to stimuli, does not consist of a cell, and is not sensitive to antibiotics.

Bacteria

A living, single-celled organism capable of reproducing on its own, responding to stimuli, metabolizing, evolving, and consisting of a cellular structure.

Helical Virus

A virus shape characterized by a long, hollow cylindrical rod with genetic material coiled inside like a spring or slinky, such as the Tobacco mosaic virus (+sense ssRNA).

Polyhedral Virus

A symmetrical, many-sided geometric viral structure featuring 20 faces, 12 corners, an internal DNA core, and a nucleocapsid (nucleic acid and capsid), exemplified by Adeno dsDNA and Rhino ss +RNA.

Enveloped Virus

A virus with a helical or icosahedral core wrapped in an outer host-derived lipid membrane with protein spikes, presenting a spherical or round appearance that is easier to deactivate with ethanol or soap.

Complex Virus

A virus possessing a combination of shapes, such as an icosahedral head connected to a helical tail or sheath and landing fibers, exemplified by bacteriophages.

DNA-Dependent DNA Polymerase

An enzyme used in replication by eukaryotes and prokaryotes that synthesizes DNA from a DNA template ($\text{DNA} \rightarrow \text{DNA}$).

DNA-Dependent RNA Polymerase

An enzyme such as RNA polymerase or DNA primase that synthesizes RNA from a DNA template during transcription ($\text{DNA} \rightarrow \text{RNA}$).

RNA-Dependent DNA Polymerase

An enzyme known as reverse transcriptase that carries out reverse transcription to synthesize DNA using an RNA template ($\text{RNA} \rightarrow \text{DNA}$).

RNA-Dependent RNA Polymerase

An enzyme (RNA replicase) that performs RNA replication by synthesizing RNA from an RNA template ($\text{RNA} \rightarrow \text{RNA}$).

Hydroxymethylcytosine (5hmC)

A modified base that replaces standard cytosine in T4 bacteriophage DNA to escape bacterial restriction-modification systems and block host CRISPR-Cas and restriction enzymes from degrading viral DNA.

Superinfection Immunity

A phenomenon observed with phage lambda where an E. coli cell carrying a resident prophage blocks transcription upon infection by a second lambda particle, preventing replication, lysis, or entry into the lytic cycle.

Lytic Cycle

A viral replication cycle in which the viral genome takes over the host's cellular machinery to synthesize viral proteins, replicate nucleic acids, assemble virions, and lyse the host cell to release progeny.

Lysogenic Cycle

A viral cycle wherein temperate phages integrate viral DNA into the host chromosome as a prophage for passive replication during host division, switching to the lytic cycle under severe stress.

Generalized Transduction

The transfer of a random piece of bacterial DNA into a recipient bacterium occurring during the lytic cycle.

Specialized Transduction

The transfer of specific bacterial genes located adjacent to the prophage insertion site, occurring during the transition from the lysogenic cycle to the lytic cycle.

Lateral Transduction

A lysogenic transfer process in which a huge portion of the host bacterial genome downstream of the prophage insertion site is transferred.

Innate Immunity

The body's built-in, fast-acting defense system that is non-specific and does not create immunological memory.

First Line of Defense

Innate physical and chemical barriers including the skin (slightly salty and acidic) and mucous membranes with their secretions, such as lysozymes.

Second Line of Defense

Internal innate defenses consisting of Natural Killer cells, phagocytic white blood cells, antimicrobial peptides (AMPs), acute inflammation signs (PRISH), and fever.

Adaptive Immunity

A slow, pathogen-specific targeted immune system developed over time following exposure to pathogens or vaccines that creates long-lasting immunological memory.

Third Line of Defense

Adaptive immune defenses comprised of specialized lymphocytes (T cells and B cells), antibodies, and immunological memory.

MHC Class I

A major histocompatibility complex molecule present on all nucleated cells that serves as a cellular identification marker.

MHC Class II

A major histocompatibility complex molecule expressed specifically on antigen-presenting cells and B cells.

Natural Killer (NK) Cells

Innate immune lymphocytes that detect and eliminate abnormal cells by recognizing the absence of an MHC Class I marker ('missing ID').

Cytotoxic Cells

Adaptive immune cells that recognize and target cells displaying a foreign or altered antigen presented on their MHC Class I molecule.

Positive-Sense ssRNA (+sense ssRNA)

Viral single-stranded RNA that can function directly as messenger RNA (mRNA) inside the host cell.

Negative-Sense ssRNA (-sense ssRNA)

Viral single-stranded RNA that must first be transcribed into a positive-sense strand using RNA-dependent RNA polymerase (RdRP) before replication and translation can occur.

Non-Enveloped Virus

A virus lacking an outer lipid membrane that requires harsher chemicals like bleach to deactivate and generally does not elicit long-lasting immune memory.

Antigenic Drift

The gradual accumulation of small mutations within viral surface protein spikes, such as hemagglutinin (HA) and neuraminidase (NA).

Antigenic Shift

A sudden, major genetic change in a virus that results in an entirely new viral subtype with novel surface proteins.

Tamiflu

An antiviral drug that blocks the enzyme required for viral particles to exit the host plasma membrane, trapping them inside to keep numbers low for immune destruction.