Microbiology Lecture: Prokaryotes, Eukaryotes, and Infectious Agents

Comprehensive vocabulary terms based on microbiology lecture notes covering cell structures, microbial classification, and viral pathology.

Prokaryote

Organisms that lack a nucleus and membrane bound organelles.

Eukaryote

Organisms that contain a nucleus and membrane bound organelles.

Flagella

Structures used for locomotion or taxis in response to photo or chemical stimuli, which can be mono-, lopho-, or amphitrichous in distribution.

Pili

An external bacterial structure used in conjugation, which is the exchange of DNA.

Fimbriae

External bacterial structures used for attachment and adhesion that allow bacteria to stick to each other and surfaces, often contributing to biofilms and pathogenicity.

S layer

A single layer of protein used for protection and/or attachment.

Capsule

A compact covering that helps bacterial cells hide from the immune system.

Slime layer

A loose covering which helps in the formation of biofilms.

Cell envelope

A structure surrounding all bacteria that offers protection against the outside world, composed of the cell wall and the cell membrane.

Cell Wall

A semi-rigid structure surrounding the cell that provides structure and cellular shape.

Cell membrane

A structure composed of a lipid bilayer embedded with proteins that utilizes selective permeability for nutrient processing and waste discharge.

Gram-positive bacteria

Bacteria that possess a thick peptidoglycan layer, teichoic acid, and lipoteichoic acid, appearing purple after Gram staining.

Gram-negative bacteria

Bacteria that possess an outer cell membrane with lipopolysaccharide (LPS), a thin peptidoglycan layer, and a periplasmic space, appearing pink after Gram staining.

Cytoplasm

A water-based solution that fills the cells.

Cytoskeleton

Long fibers of proteins that encircle the cell just beneath the cytoplasmic membrane to help shape the cell.

Inclusion granules

Storage sites for nutrients such as glycogen, fat, and phosphate during periods of abundance.

Ribosomes

Structures composed of RNA and protein that serve as the site of protein synthesis.

Nucleoid

A dense area of the cytoplasm where bacterial chromosomes are aggregated.

Endospores

Structures composed of calcium and dipicolinic acid that protect genetic material during harsh conditions and are resistant to heat, drying, and radiation.

Plasmids

Separate, nonessential, double-stranded circles of DNA found in addition to essential chromosomes.

Archaea

Organisms with cell walls composed of chemicals other than peptidoglycan (such as polysaccharides or proteins) and ribosomal RNA distinct from bacteria.

Methanogens

The largest group of archaea which convert carbon dioxide and hydrogen into methane gas.

Stages of mitosis

Prophase, metaphase, anaphase, and telophase.

Microscopic Fungi

Eukaryotic organisms such as mold and yeast; some are dimorphic and can exist in either form.

Protists

Unicellular, eukaryotic organisms that include protozoa and algae.

Helminths

Multicellular organisms including flatworms and roundworms that have reproductive, nervous, and muscular systems.

Hermaphrodite

A term describing a helminth that possesses both male and female sex organs in the same worm.

Viruses

Small infectious particles composed of nucleic acids, capsids, and sometimes envelopes.

Capsid

A protector layer found in all viruses composed of individual proteins called capsomeres.

Naked virus

A virus composed only of a capsid surrounding nucleic acids, without an external membrane.

Enveloped virus

A virus that has a membrane (acquired from the host cell during release) surrounding the capsid and nucleic acid.

Viral protein spikes

Structures composed of glycoproteins that protrude from the viral surface to help the virus attach to a host cell.

Prions

Proteins in brain cells capable of folding into a normal structure ($\alpha\text{-helix}$) or a misfolded structure ($\beta\text{-pleated}$).

Spongiform encephalopathies

Diseases caused by misfolded prions that destroy brain matter, resulting in large vacuoles and a spongy appearance.

Viroids

Small, circular pieces of infectious RNA that lack a protein coat and are pathogenic in plants and fungi.

Multiplication cycle of RNA animal viruses

A sequence of six steps: adsorption, penetration uncoating, synthesis, assembly, and release.

Provirus

A viral genome that has been incorporated into the host genome.

Latent

The state of an inactive virus.

Chronic Latent State

A condition where inactive viruses are periodically reactivated.