Bacteria and archaea

Taxonomy

The science of classification of organisms.

Phylogeny

The interrelatedness of organisms, often illustrated by phylogenetic trees showing common ancestors.

Domains of Life

The three major domains of life based on ribosomal RNA genes: Archaea, Bacteria, Eukarya.

5 Kingdom System

A system of classification that includes five kingdoms: Animalia, Plantae, Mycetae, Protista, Monera.

Genotypic Classification

Classification based on genetic information, specifically RNA sequences.

Phenotypic Classification

Classification based on observable characteristics of organisms.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer that retain the crystal violet stain.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane that do not retain the crystal violet stain.

Endospore Formation

The process by which bacteria form a dormant and resistant structure called an endospore.

Bacterial Species Definition

A species in bacteria is defined by genetics and phenotypic characteristics, including differences in cell wall.

Strain

Different versions of the same bacterial species with genetic variations.

Methanogens

Archaea that convert carbon dioxide and hydrogen into methane.

Extreme Halophiles

Archaea that thrive in high salt environments, often utilizing pigments for ATP synthesis.

Periplasmic Space

The area between the inner cytoplasmic membrane and the outer membrane in gram-negative bacteria.

Peptidoglycan

A compound in bacterial cell walls composed of sugar chains cross-linked by peptide fragments.

Fimbriae

Hairlike structures that help bacteria adhere to surfaces.

Pili

Long structures that facilitate conjugation between bacterial cells.

Capsule

A protective outer layer around some bacterial cells that aids in adhesion and evasion of the immune response.

Flagella

Long, whip-like structures that enable bacterial motility and self-propulsion.

Chemotaxis

The movement of bacteria in response to chemical signals, either towards or away from stimuli.

Coccus/Cocci

Spherical-shaped bacteria, which can exist as single cells or in arrangements such as chains or clusters.

Bacillus/Bacilli

Rod-shaped bacteria that can also exist individually or in chains.

Vibrio

Gently curved rod-shaped bacteria.

Spirillum

Long and rigid cylindrical bacteria that are spiral in shape.

Spirochete

Flexible, spiral-shaped bacteria.

Teichoic Acids

Polysaccharides found in the cell walls of gram-positive bacteria that aid in cell wall maintenance.

Lipopolysaccharide

A complex of lipid and carbohydrate found in the outer membrane of gram-negative bacteria that acts as an endotoxin.