Microbiology: Viroids, Prions, and Prokaryotes

Flashcards covering the characteristics, classification, structure, and functions of viroids, prions, and prokaryotes (bacteria and archaea).

Viroids

Small, circular molecules of naked circular RNA that are infectious agents in plants and lack a protein coat.

Prions

Disease-causing particles consisting of a misfolded form of a protein that do not contain DNA or RNA.

Mad Cow Disease

A degenerative brain disease caused by prions.

Prokaryote

A single-celled organism that lacks a true nucleus and membrane-bound organelles.

Monera

The single kingdom into which all prokaryotes were formerly placed before being divided into two domains.

Archaea

A domain of prokaryotes whose name means "archaic or ancient" and often live in extreme environments.

Peptidoglycans

A polysaccharide found in the cell walls of eubacteria but absent in the cell walls of archaebacteria.

Methanogens

A group of archaea that convert hydrogen gas and $CO_2$ into methane gas and must live in anaerobic environments.

Halophiles

Archaeal organisms known as "salt-loving" that live in environments with very high salt concentrations.

Thermoacidophiles

Archaea that live in very acidic environments with temperatures up to $110\,^\circ\text{C}$ and a pH of less than $2$.

Black smokers

Hydrothermal vents that leak hot, dark-colored, acidic water where thermoacidophilic archaea are often found.

Eubacteria

The "true" bacteria kingdom characterized by cell walls containing peptidoglycan.

Cocci

Spherical-shaped bacteria.

Bacilli

Rod-shaped bacteria.

Spirilla

Spiral-shaped or curved bacteria.

Flagella

Long, whip-like structures used by some bacteria for movement.

Capsule

A gluey polysaccharide layer outside the cell wall that protects bacteria from dehydration or the host's immune system.

Pili

Structures shorter and thinner than flagella used to attach bacteria to food sources, liquid surfaces, or other bacteria during reproduction.

Plasmid DNA

A small, circular piece of DNA separate from the chromosome, generally containing one gene.

Saprophytes

Heterotrophic bacteria that live on dead organic matter and act as decomposers.

Parasites

Organisms that invade and live off of plants and animals (the host).

Photoautotrophs

Photosynthetic organisms that use light energy to convert carbon dioxide and water into glucose and oxygen.

Chemoautotrophs

Organisms that use energy from inorganic reactions to build molecules of glucose.

Obligate aerobes

Organisms that require a constant supply of oxygen to live.

Obligate anaerobes

Organisms that do not require oxygen and are killed by its presence.

Facultative anaerobes

Organisms that do not require oxygen but are not killed by it, allowing them to live with or without oxygen.

Binary fission

A type of asexual reproduction where a cell replicates its DNA and divides in half to form two identical daughter cells.

Conjugation

A process where a hollow bridge forms between two bacterial cells to transfer genetic information, increasing genetic diversity.

Endospores

Dormant structures formed inside a bacterial cell under unfavorable conditions to survive extreme dryness, heat, or cold.

Nitrogen fixation

The process by which bacteria convert nitrogen gas into nitrates that plants can use.

Pathogens

Disease-causing agents that can damage host tissues directly or release toxins.

Vaccine

A weakened or killed form of a pathogen used to stimulate the immune system to produce antibodies and provide immunity.

Antibiotics

Compounds that kill bacteria but have no effect on viruses.

Symbiosis

A close and permanent association between organisms of different species.

Mutualism

A symbiotic relationship that is beneficial to both species.

Commensalism

A relationship in which one species benefits while the other is neither harmed nor helped.

Parasitism

A relationship in which one species benefits while the other is harmed.