Archaea and Bacteria

Prokaryote

A unicellular organism that lacks a nucleus and membrane-bound organelles; includes Bacteria and Archaea.

Biomass

The total mass of living organisms in an area.

Heterotroph

An organism that obtains organic molecules by consuming other organisms or organic matter.

Autotroph

An organism that produces its own organic molecules from inorganic substances.

Aerobe

An organism that requires oxygen (O₂) for survival.

Anaerobe

An organism that cannot tolerate oxygen.

Facultative Anaerobe

An organism that can survive with or without oxygen.

Nitrogen Fixation

The conversion of atmospheric nitrogen (N₂) into biologically usable forms.

Decomposer

An organism that breaks down dead organic matter and recycles nutrients.

Binary Fission

Asexual reproduction in which one prokaryotic cell divides into two genetically identical cells.

Horizontal Gene Transfer

Movement of genes between unrelated organisms.

Vertical Gene Transfer

Transmission of genes from parent to offspring.

Transformation

The uptake of free DNA from the environment by a bacterial cell.

Transduction

The transfer of DNA between bacteria by a bacteriophage.

Conjugation

Direct transfer of DNA between bacterial cells through a physical connection.

Sex Pilus

A tube-like structure used in bacterial conjugation.

Plasmid

A small circular DNA molecule separate from the bacterial chromosome.

Plasmid Transfer

The movement of plasmids between bacteria.

Bacteriophage (Phage)

A virus that infects bacteria and may transfer DNA.

Biofilm

An organized colony of microorganisms attached to a surface.

Microbiome

The collection of microorganisms living in and on an organism.

Symbiosis

A close relationship between different species.

Domain

The highest taxonomic classification level.

Three-Domain System

A system classifying life into Bacteria, Archaea, and Eukarya.

Monera

An obsolete kingdom once used to classify all prokaryotes.

Eukarya

The domain containing organisms with nuclei and membrane-bound organelles.

Common Ancestor

An ancestral organism from which multiple lineages evolved.

Bacteria

A domain of prokaryotes with peptidoglycan-containing cell walls.

Pathogen

A microorganism capable of causing disease.

Probiotic Bacteria

Beneficial bacteria that support gut health.

Bioremediation

The use of organisms to remove pollutants from the environment.

Cell Wall

A protective layer that maintains cell shape and prevents bursting.

Peptidoglycan

A strong mesh-like polymer that forms bacterial cell walls.

Function of Peptidoglycan

Provides support, maintains shape, and prevents osmotic rupture.

Gram Stain

A staining technique used to classify bacteria by cell wall structure.

Gram-Positive Bacteria

Bacteria with thick peptidoglycan cell walls.

Gram-Negative Bacteria

Bacteria with thin peptidoglycan layers and an outer membrane.

Endospore

A resistant dormant structure formed by some bacteria.

Thylakoid

A membrane structure used for photosynthesis in some bacteria.

Magnetosome

A magnetic structure that helps bacteria locate low-oxygen environments.

Cyanobacteria

Photosynthetic bacteria that produce oxygen and are ancestors of chloroplasts.

Cyanobacterial Bloom

Rapid growth of cyanobacteria that may release toxins.

Proteobacteria

A highly diverse group of bacteria that includes many important species.

Rhizobium

A nitrogen-fixing proteobacterium associated with plant roots.

Vibrio

A proteobacterium involved in squid bioluminescence.

Agrobacterium tumefaciens

A bacterium that causes tumor-like growths in plants.

Helicobacter

A bacterium associated with stomach ulcers.

Mitochondrial Ancestor Theory

The idea that proteobacteria gave rise to mitochondria.

Chlamydia

A bacterial phylum consisting of intracellular parasites.

Spirochete

A spiral-shaped bacterium.

Streptomyces

Gram-positive bacteria that produce many antibiotics.

Mycoplasma

Small bacteria that lack cell walls.

Archaea

A domain of prokaryotes more closely related to Eukarya