BIO 205 – Microbiology Chapter 6 Study Guide

Flashcards covering key vocabulary, structures, life cycles, and genetic transfer mechanisms related to viruses, viroids, virusoids, prions, and bacteria from Chapter 6 of BIO 205 Microbiology.

Capsid

The protein coat that encloses the nucleic acid of a virus. Found in all viruses.

Nucleic Acid (Viral)

The genetic material of a virus (DNA or RNA). Found in all viruses.

Viral Envelope

A lipid bilayer surrounding the capsid of some viruses, derived from the host cell membrane.

Spikes

Glycoproteins on the viral envelope or capsid that aid in attachment to host cells. Found in some viruses.

Virion

A complete, infective virus particle outside a host cell.

Helical Capsid

A viral capsid structure where proteins are arranged in a cylindrical helix.

Polyhedral Capsid

A viral capsid structure with multiple flat faces, often icosahedral (20 triangular faces).

Complex Capsid

A viral capsid structure combining helical and polyhedral components, or having additional elaborate structures (e.g., bacteriophages).

Host Range (Virus)

The specific range of host cells or organisms that a particular virus can infect, determined by specific receptor interactions.

Attachment (Viral Life Cycle)

The first step where a virus binds to specific receptors on the host cell surface.

Penetration (Viral Life Cycle)

The second step where the virus enters the host cell after attachment.

Biosynthesis (Viral Life Cycle)

The third step where viral nucleic acid directs the host cell's machinery to produce viral components (proteins and nucleic acids).

Maturation (Viral Life Cycle)

The fourth step where new viral nucleic acids and proteins assemble into virions.

Release (Viral Life Cycle)

The final step where newly formed virions exit the host cell.

Lytic Cycle

A bacteriophage life cycle where the virus replicates and causes lysis (destruction) of the host cell to release new virions.

Lysogenic Cycle

A bacteriophage life cycle where viral DNA integrates into the host bacterial chromosome (prophage) and replicates with the host genome without immediate lysis.

Prophage

Phage DNA that has integrated into the bacterial chromosome during the lysogenic cycle.

Phage Conversion

A change in the phenotype of a bacterium due to the presence of a prophage, often conferring new properties like toxin production.

Consequences of Lysogeny

Include immunity to superinfection by the same phage, phage conversion, and specialized transduction.

Fusion (Viral Penetration)

A method of viral entry where the viral envelope merges with the host cell membrane, releasing the capsid into the cytoplasm. Requires an enveloped virus.

Endocytosis (Viral Penetration)

A method of viral entry where the host cell engulfs the virus in a vesicle, followed by uncoating. Can occur with both enveloped and naked viruses.

+RNA Virus Replication

Replication where the viral +RNA acts directly as mRNA for protein synthesis and as a template for -RNA, which then serves as a template for new +RNA.

-RNA Virus Replication

Replication where the viral -RNA must first be transcribed into +RNA by a viral RNA-dependent RNA polymerase for protein synthesis and as a template for new -RNA.

dsRNA Virus Replication

Replication involving a double-stranded RNA genome, where one strand is transcribed into +mRNA by viral RNA polymerase for protein synthesis, and also serves as a template for new dsRNA.

Retrovirus

An RNA virus that uniqueley uses reverse transcriptase to synthesize DNA from its RNA genome, which then integrates into the host chromosome.

Reverse Transcriptase

An enzyme found in retroviruses that synthesizes DNA from an RNA template.

Integrase

An enzyme in retroviruses that integrates the newly synthesized viral DNA into the host cell's chromosome.

Protease (Retrovirus)

An enzyme in retroviruses that cleaves large viral polyproteins into functional individual proteins required for virion assembly.

Viroid

A short, naked, circular single-stranded RNA molecule that causes plant diseases and lacks a protein coat.

Virusoid

A circular single-stranded RNA molecule that requires a helper virus to replicate and infect, often encapsulated in the helper virus's capsid.

Prion

An infectious protein particle that lacks nucleic acid and causes neurological diseases by inducing misfolding of normal host proteins.

Prion Propagation

The process where misfolded prion proteins (PrPsc) convert normal host prion proteins (PrPc) into more misfolded PrPsc.

Vertical Gene Transfer

Transmission of genetic information from parent to offspring.

Horizontal Gene Transfer (HGT)

Transfer of genetic material between independent organisms, not via reproduction.

Conjugation (Bacteria)

A type of HGT where genetic material (often plasmids) is directly transferred between two bacterial cells in physical contact, typically via a pilus.

Transformation (Bacteria)

A type of HGT where a bacterial cell takes up naked DNA from its environment.

Transduction (Bacteria)

A type of HGT where bacterial DNA is transferred from one bacterium to another via a bacteriophage.

Gram-Negative Conjugation

Occurs via a sex pilus that directly connects donor and recipient cells for gene transfer.

Gram-Positive Conjugation

Often involves adhesive proteins that cause cells to aggregate, followed by direct transfer of genetic material without a pilus.