BIO 205 - Microbiology: Chapter 6 Study Guide

Vocabulary flashcards for Microbiology Chapter 6, covering viral structure, life cycles, replication, and related concepts.

Viral components (all viruses)

Nucleic acid (DNA or RNA) and a protein coat (capsid).

Viral components (some viruses)

An outer lipid envelope and/or enzymes.

Helical capsid

A rod-shaped capsid where capsomeres are arranged helically around the nucleic acid.

Icosahedral capsid

A polyhedral (often 20-sided) capsid made of capsomeres forming a geometrically regular structure.

Complex capsid

Capsids that have intricate structures, often combining features of helical and icosahedral shapes (e.g., bacteriophages).

Host range

The specific range of host cells a virus can infect, determined by specific receptor sites on the host cell surface and the virus's attachment proteins.

Attachment (viral life cycle)

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

Penetration (viral life cycle)

The second step where the virus (or its genetic material) enters the host cell.

Biosynthesis (viral life cycle)

The third step where the viral nucleic acid is replicated, and viral proteins are synthesized using the host cell's machinery.

Maturation (viral life cycle)

The fourth step where new virions are assembled from the newly synthesized nucleic acid and proteins.

Release (viral life cycle)

The final step where newly formed viruses exit the host cell, often by lysis (bursting) or budding.

Lytic cycle (bacteriophage)

A viral life cycle in which the virus replicates in the host cell and then lyses (bursts) the cell open to release new virions.

Lysogenic cycle (bacteriophage)

A viral life cycle in which the viral DNA integrates into the host bacterial chromosome and replicates along with it, without killing the host cell immediately.

Phage conversion

A phenomenon where a bacterium exhibits new properties after being infected by a lysogenic bacteriophage due to genes carried by the prophage.

Consequences of lysogeny for host cell

1. Immunity to superinfection by the same or similar phages. 2. Phage conversion of the host's phenotype. 3. Specialized transduction of bacterial genes.

Penetration by fusion

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

Penetration by endocytosis

A type of viral entry where the host cell engulfs the virus (enveloped or non-enveloped) in a vesicle (endosome).

Single-stranded + RNA virus replication

Uses its (+) sense RNA directly as mRNA for protein synthesis; also serves as a template for synthesizing (-) sense RNA, which then serves as a template for more (+) sense RNA.

Single-stranded - RNA virus replication

Carries its own RNA-dependent RNA polymerase to transcribe its (-) sense RNA into (+) sense mRNA, which is then translated. The (+) sense RNA also serves as a template for new (-) sense RNA genomes.

Double-stranded RNA virus replication

Carries its own RNA-dependent RNA polymerase to transcribe one strand of its dsRNA into (+) sense mRNA for protein synthesis and as a template for synthesizing new dsRNA genomes.

Retrovirus

An RNA virus that converts its RNA genome into DNA using an enzyme called reverse transcriptase, which is then integrated into the host cell's genome.

Reverse transcriptase (retrovirus)

An enzyme unique to retroviruses that synthesizes DNA from an RNA template, a process that is