Bacteria | Structure and Function

Flagella

A long appendage that provides motility to bacteria, allowing them to move through their environment.

Fimbre

Short, thin appendages on bacteria that aid in attachment to surfaces but are not primarily for movement.

Pilus

A longer, less frequent appendage on bacteria that facilitates connection between bacterial cells, often used in conjugation.

Cell Envelope

The protective layer surrounding bacteria, composed of multiple layers including the cell wall and membrane.

Nucleoid

The region in a bacterial cell where the DNA is located, as bacteria do not have a defined nucleus.

Endospore

A specialized structure formed by some bacteria to withstand harsh conditions, allowing for survival.

Ribosomes

Cellular structures in bacteria responsible for protein synthesis, appearing as small dots in the cytoplasm.

Bacterial Chromosome

The main DNA structure in bacteria, typically a single circular strand, located in the nucleoid.

Plasmid

A small, circular piece of DNA found in some bacteria, separate from the bacterial chromosome.

Monotrichous

Bacteria configuration with a single flagellum at one pole.

Lophotrichous

Bacterial configuration with multiple flagella originating from one polar end.

Amphitrichous

Bacteria configuration with flagella located at both polar ends.

Peritrichous

Bacterial configuration with flagella distributed over the entire surface.

Cell Wall

A rigid structure that provides shape and protection to bacterial cells, composed primarily of peptidoglycan.

Capsule

A thick, gelatinous layer outside the cell wall that aids in protection against phagocytosis and helps with adhesion.

Biofilm

A complex community of microorganisms that adhere to surfaces and are enclosed in a protective matrix.

Facultative Anaerobes

Bacteria that can survive with or without oxygen, using aerobic respiration or fermentation.

Obligate Anaerobes

Bacteria that are poisoned by oxygen and can only survive in an oxygen-free environment.

Gram-Positive

Bacteria that retain the crystal violet stain used in the Gram staining procedure, appearing purple under a microscope.

Gram-Negative

Bacteria that do not retain the crystal violet stain and appear pink, possessing a thinner peptidoglycan layer and an outer membrane.

Transformation

The process by which a bacterial cell takes up and incorporates foreign DNA from its environment.

Transduction

A mechanism of horizontal gene transfer where bacterial DNA is transferred by a virus (bacteriophage).

Conjugation

The direct transfer of genetic material between bacterial cells through a pilus.