Infectious Diseases and Pathogens

Comprehensive vocabulary flashcards covering infectious disease concepts, viral and bacterial biology, and specific fungal and protist pathogens based on lecture notes.

Infectious disease

Any condition that interferes with how an organism, or any part of it, functions, caused by pathogens and transmissible from one host to another.

Pathogen

A disease-causing agent.

Cellular pathogens

Living organisms made of cells that can grow, reproduce, carry out metabolic processes, and respond to the environment.

Bacteria

Microscopic, unicellular, prokaryotic organisms that lack a nuclear membrane and membrane-bound organelles.

Fungi

Spore-producing eukaryotic organisms that can be unicellular (e.g., yeasts) or multicellular (e.g., moulds).

Parasites

Organisms that live on or in a host for all or part of their life, causing harm; often multicellular.

Protozoa

Unicellular eukaryotes, such as those causing Malaria or Toxoplasmosis.

Non-Cellular pathogens

Agents not made of cells and not considered living; they cannot reproduce on their own and require a host cell.

Viruses

Non-cellular pathogens containing DNA or RNA that can only reproduce inside a living host cell.

Prions

Misfolded proteins that cause other proteins to misfold into an incorrect $3D$ shape, leading to harmful protein sticking.

Attachment (Viral Replication)

The process where a virus attaches to specific receptor proteins on the surface of a host cell.

Penetration (Viral Entry)

The process where a virus or its genetic material (DNA/RNA) enters the host cell and is released into the cell environment.

Virions

Complete viruses formed when new viral DNA/RNA and viral proteins are assembled at the host cell membrane.

Bacteriophage

A virus that specifically infects, invades, and replicates within bacterial cells.

Lysis

The process in which a bacterial cell bursts open, resulting in host cell death and the release of newly formed bacteriophages.

Transmission

The transport of a pathogen from an infected host or a reservoir to a susceptible host.

Reservoir

An organism or environment, such as humans, soil, or water, in which a pathogen normally lives, survives, and reproduces.

Host

An organism that is infected by a pathogen.

Vector (diseases)

A living organism, such as a mosquito or flea, that transmits pathogens from one host to another.

Fomite

A non-living object or material, such as door handles, that carries a pathogen.

Zoonosis

An infectious disease, such as Rabies or Ebola, that can be transmitted naturally between vertebrate animals and humans.

Spillover

The transmission of a pathogen from its usual animal host into a new species, such as humans.

Non-infectious diseases

Diseases not caused by pathogens and which cannot be transmitted between organisms; examples include Diabetes and cancer.

Peptidoglycan

A protein-carbohydrate compound that forms the cell wall of bacteria.

Plasmids

Small circular loops of DNA separate from the chromosome in bacteria that replicate independently and often contain antibiotic resistance genes.

Flagellum

A long whip-like or tail-like structure that allows for movement in some bacteria, protists, and zoospores.

Capsule (slime layer)

A thick layer outside the bacterial cell wall that helps bacteria stick to surfaces and protects them from the host immune system.

Endospores

Tough, dormant structures formed by some bacteria that are resistant to extreme temperatures, chemicals, and drying out.

Binary Fission

The main method of bacterial reproduction where a single cell replicates its genetic material and divides into two identical daughter cells.

Gram-positive bacteria

Bacteria with a thick peptidoglycan cell wall that appear purple after Gram staining.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane that appear pink to red after taking up safranin counterstain.

Hyphae

A network of long, thin branching filaments that make up most multicellular fungi and provide a high SA:V ratio for nutrient absorption.

Mycelium

An interconnected network of hyphae that forms the main body of a fungus.

Chitin

The material that makes up the cell wall of fungi, providing strength, support, and protection.

Septa

Cross walls that may divide fungal hyphae into compartments.

Sporangia

Structures formed by mature mycelium that produce and release spores into the environment.

Chytridiomycosis

A disease in amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis ($Bd$), which damages the keratin layer of the skin.

Protists

Typically unicellular eukaryotic organisms that inhabit aquatic or moist environments and can be animal-like, plant-like, or fungus-like.

Cilia

Tiny hair-like structures protruding from the cell that some protists use for movement.

Pseudopodia

Temporary arm-like projections used by some protists for movement and ingestion.

Plasmodium

The genus of parasitic, animal-like protists (protozoa) that cause Malaria.

Sporozoites

The form of the Plasmodium pathogen injected into the bloodstream by an infected female Anopheles mosquito.

Phytophthora

A fungus-like protist classified as an oomycete (water mould) that causes Dieback in terrestrial plants.

Zoospores

Motile spores produced by oomycetes like Phytophthora that possess flagella and move through water in soil to infect plant roots.