Bacteria Notes

Eukaryotic cells

Cells found in animals, plants, fungi, and protists that contain a double-membrane bound nucleus with DNA chromosomes and membrane-bound organelles.

Prokaryotic cells

Cells found in bacteria and archaea that lack a nucleus and other membrane-bound organelles.

Flagella

Long protein structures used for cell motility in bacteria. They consist of a filament, hook, and basal body and can rotate 360 degrees.

Fimbriae

Fine, hairlike protein bristles on the cell surface that function in adhesion to other cells and surfaces.

Pili

Rigid tubular structures made of pilin protein that join bacterial cells for partial DNA transfer called conjugation. They are found only in Gram-negative bacteria.

Glycocalyx

The outermost layer of the cell that is used for protection and helps cells adhere to surfaces. It can be in the form of a slime layer or a capsule.

Cell membrane

A lipid bilayer that surrounds the cytoplasm and defines the boundary of the cell. It is selectively permeable and functions in nutrient processing, synthesis, and selective permeability.

Cell wall

Helps determine the shape of a bacterium and provides structural support. It is composed of peptidoglycan and is found in both Gram-positive and Gram-negative bacteria.

Gram stain

A differential stain used to classify bacteria into Gram-positive and Gram-negative based on their cell wall structure. Gram-positive bacteria retain crystal violet and stain purple, while Gram-negative bacteria lose crystal violet and stain red.

Acid-fast bacteria

Bacteria with a different structure than Gram-positive and Gram-negative bacteria, containing more lipid (mycolic acid). They are highly resistant to certain chemicals and are responsible for diseases like tuberculosis and leprosy.

Mycoplasmas

Bacteria without a cell wall that contain sterols in their membrane to prevent lysis. They can have a variety of shapes and are responsible for diseases like walking pneumonia.

Chromosome

The genetic material in the nucleoid of a bacterial cell. It carries the information required for maintenance and growth.

Plasmids

Extra pieces of genetic material that carry genes not essential for survival. They can be advantageous and passed onto offspring.

Ribosomes

Structures involved in protein synthesis that facilitate the joining of amino acids to make a protein.

Inclusions and granules

Intracellular storage bodies that perform various functions and store nutrients when environmental sources are depleted.

Endospores

Dormant structures produced by certain Gram-positive bacteria, such as Clostridium and Bacillus. They are highly resistant and can survive for a very long time in adverse environmental conditions.

Bacterial shapes

Bacteria can vary in shape, size, and arrangement. The three basic shapes are cocci (spherical), bacilli (rod-shaped), and spirilla (helical or spiral-shaped).

Archaea

A domain of prokaryotes that are more closely related to Eukarya than to Bacteria. They have unique genetic sequences, membrane lipids, and cell walls, and live in extreme habitats.

Monotrichous

single flagellum at one end

Lophotrichous

small bunches arising from one end of cell

Amphitrichous

flagella at both ends of cell

Peritrichous

flagella dispersed over surface of cell; slowest