Microbiology Lecture Flashcards: Chapters 6, 7, 9, 10, and 15

Practice flashcards covering virology, microbial growth, epidemiology, pathogenicity, and antimicrobial drug mechanisms as discussed in the lecture transcript.

Capsid

A protein shell that packages and protects the viral genome, constituting the bulk of a virion's mass and composed of subunits called capsomeres.

Spikes (Peplomers)

Glycoprotein extensions protruding from the viral capsid or envelope that help the virus attach to and gain entry into specific host cells.

RNA-dependent RNA polymerases (RdRPs)

Enzymes used by single-stranded negative (antisense) RNA viruses to transcribe their genome into mRNA.

Antigenic Drift

Minor genetic mutations in a virus's genome (e.g., influenza) that cause small changes in the HA and NA spikes.

Antigenic Shift

A major genetic reassortment in viruses that leads to dramatic changes in surface spikes, often leading to increased infectivity or expanded host range.

Tropism

The specificity of a virus for particular host tissues or cell types determined by viral surface factors.

Lytic Replication Pathway

A viral replication process where the virus infects the host, builds new virions, and kills the host cell upon release.

Lysogenic Replication

A replication pathway where the phage genome is incorporated into the host cell genome, forming a prophage that is copied as the cell divides.

Phage Conversion

The process by which prophages confer new pathogenic properties, such as the ability to produce toxins, to bacterial cells.

Provirus

The integrated viral genome of a retrovirus (like HIV) into the host cell's DNA.

Plaque-forming units (PFUs)

The quantity of bacteriophages in an initial volume of sample, where each plaque on a bacterial lawn represents a single phage.

Prions

Infectious protein particles that contain no genetic material and cause transmissible spongiform encephalopathies (TSEs).

Binary Fission

An asexual process occurring in most prokaryotes where a single cell divides into two genetically identical daughter cells.

Generation Time

The time it takes for a particular bacterium to double in number.

Lag Phase

A period of delay in bacterial growth where cells adjust to their new environment before beginning to divide.

Psychrophiles

Microbes that thrive in cold temperatures between $-20$ and $10\,^{\circ}\text{C}$.

Mesophiles

Microbes that grow best between $10$ and $50\,^{\circ}\text{C}$, representing the group containing most human pathogens.

Halophiles

Microbes that thrive in high-salt environments, tolerating concentrations up to $35\%$.

Facultative Anaerobes

Organisms that can grow with or without oxygen but prefer using oxygen for metabolism.

Reactive Oxygen Species (ROS)

Chemically reactive molecules containing oxygen that can rapidly damage proteins and DNA; aerotolerant and aerobic microbes must deactivate them.

Autotrophs

Organisms that do not require an external source of organic carbon; they use carbon fixation to convert inorganic $CO_2$ into organic carbon.

Defined Media (Synthetic Media)

Growth media with a precisely known and quantified chemical composition for every organic and inorganic component.

Differential Media

Media formulated to visually distinguish one microbe from another based on their biochemical activities, such as blood agar.

Selective Media

Media containing ingredients that foster the growth of specific bacteria while suppressing the growth of others, like Mannitol Salt Agar.

Colony-forming units (CFUs)

A measure used in viable plate counts to represent the number of living cells, accounting for the fact that clumps of cells can give rise to a single colony.

Sterilization

The process of eliminating all bacteria, viruses, and endospores from an object or environment.

Autoclave

A machine that uses steam heat ($121\,^{\circ}\text{C}$) and pressure ($15\,\text{psi}$) to achieve sterilization.

HEPA Filters

High-efficiency particulate air filters that remove $99.97\%$ of airborne substances but do not strictly sterilize the air.

Antiseptics

Germicides that are safe to apply directly to living tissue.

Epidemic

A widespread disease outbreak in a particular region during a specific time frame.

Zoonotic Diseases

Diseases that spread from animals to humans.

Incubation Period

The time interval between infection and the development of the first clinical symptoms of a disease.

Pathogenicity

The general ability of a microbe to cause disease.

Virulence

The degree or extent of disease that a pathogen causes.

$R_0$ (R-naught)

The basic reproduction number; a measure of a pathogen’s transmissibility representing how many people one infected person will infect in a fully susceptible population.

ID50 (Infectious Dose-50)

The number of pathogens or virions needed to establish an infection in $50\%$ of exposed hosts.

Endotoxin

The lipid A region of lipopolysaccharide (LPS) found in the outer membrane of Gram-negative bacteria that triggers fever and potential septic shock.

AB Toxins

Type III exotoxins consisting of a binding (B) region and an active (A) portion that exerts effects inside the host cell.

Adhesins

Virulence factors such as capsules, fimbriae, or pili that pathogens use to stick to host cells.

Siderophores

Specialized tools secreted by pathogens to scavenge and steal iron from host tissues.

Biosafety Level 4 (BSL-4)

The highest containment level for dangerous, 'exotic,' and often lethal pathogens for which there are no treatments (e.g., Ebola virus).

Empiric Therapy

Treatment initiated based on clinical presentation before definitive or complete clinical data is available.

Therapeutic Index

The ratio of the maximum tolerated dose of a drug to the minimum effective dose; higher values are considered safer.

Beta-lactam Drugs

A large class of bactericidal antibiotics, including penicillins and cephalosporins, that target bacterial cell wall construction.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial drug that inhibits the visible growth of a microbe.

Efflux Pumps

Transporters used by some bacteria to pump drugs out of the cell, effectively reducing drug concentration and contributing to antimicrobial resistance.