Microbiology — Bacteria & Viruses

Capsid

The protein shell that encases the genetic material of a virus.

Lysogenic cycle

A viral replication cycle where the virus integrates its DNA into the host cell's genome, remaining dormant until triggered to enter the lytic cycle.

Lytic cycle

A viral replication cycle that results in the destruction of the host cell and the release of new viral particles.

What is the role of reverse transcriptase in retroviruses?

Reverse transcriptase is an enzyme that synthesizes DNA from an RNA template, a key step in the replication of retroviruses like HIV.

Transformation in bacteria

The process by which bacteria take up extracellular DNA from their environment.

Transduction

The transfer of genetic material from one bacterium to another via a bacteriophage.

Endospore

A resistant, dormant structure formed by some bacteria that can survive extreme conditions.

What is the significance of the operon model in bacteria?

The operon model explains the regulation of gene expression in bacteria, allowing for coordinated control of genes with related functions.

Obligate anaerobes

Microorganisms that cannot survive in the presence of oxygen.

Facultative anaerobes

Microorganisms that can grow with or without oxygen, using it when available.

What is quorum sensing?

A mechanism by which bacteria regulate gene expression in response to population density through the release and detection of signaling molecules.

Plasmid

A small, circular DNA molecule found in bacteria that can replicate independently of the chromosomal DNA.

What determines the host range of a virus?

The host range is determined by the virus's ability to attach and enter a host cell, often dictated by specific receptor-ligand interactions.

Bacteriophage

A virus that infects and replicates within bacteria.

What is the purpose of the CRISPR-Cas system in bacteria?

The CRISPR-Cas system provides adaptive immunity against phages by storing segments of phage DNA and using them to recognize and cut foreign DNA.

Biofilm

A complex community of microorganisms growing on a surface, embedded in a self-produced extracellular matrix.

What is the significance of the 16S rRNA gene in bacterial classification?

The 16S rRNA gene is highly conserved and used as a molecular marker for phylogenetic studies and identification of bacteria.

Antibiotic resistance

The ability of bacteria to survive and grow in the presence of an antibiotic that would normally inhibit or kill them.

What is the role of hemagglutinin in the influenza virus?

Hemagglutinin is a glycoprotein that facilitates viral entry into host cells by binding to sialic acid receptors on the cell surface.

Virion

The complete, infectious form of a virus outside a host cell, consisting of the genetic material and a protein coat.

What is a bacterium's flagellum used for?

A flagellum is a whip-like structure that provides motility to bacteria, allowing them to swim toward favorable environments.

Pathogenicity island

A distinct genetic element that carries genes for virulence factors, often acquired through horizontal gene transfer.

Viroid

A small, circular RNA molecule that infects plants, lacking a protein coat and not encoding proteins.

Prion

A misfolded protein that can induce other proteins to misfold, associated with neurodegenerative diseases.

What is an obligate intracellular parasite?

An organism, such as a virus, that can only reproduce inside the cells of a host organism.

Zoonosis

An infectious disease that can be transmitted from animals to humans.

What is antigenic drift?

A gradual process of genetic mutation in viruses, such as influenza, leading to changes in surface proteins and evasion of host immunity.