Differential staining methods

Gram's Stain Method

A differential staining technique used to classify bacteria into two groups (Gram-positive and Gram-negative) based on the structure of their cell walls.

Bacterial Cell Envelope

Consists of the cell membrane and cell wall; distinguishes between Gram-positive and Gram-negative bacteria.

Peptidoglycan

A crucial structural component of the bacterial cell wall, especially abundant in Gram-positive bacteria.

Nucleoid

The region in bacterial cells where the DNA chromosome is located, not enclosed by a nuclear membrane.

Capsule

A gelatinous layer made of polysaccharides that surrounds some bacterial cells, important for survival in host organisms.

Flagella

Long, whip-like structures composed of protein subunits (flagellin) that provide motility to bacteria.

Fimbriae (Pili)

Hairlike structures on bacteria that facilitate attachment to surfaces and other cells.

Acid-Fast Stain (Ziehl-Neelsen Stain)

A staining method used to identify bacteria with waxy cell walls, such as Mycobacterium species.

Differential Staining

A technique used to distinguish between different types of bacteria by applying specific stains.

Lipopolysaccharides (LPS)

Large molecules found in the outer membrane of Gram-negative bacteria; they can act as endotoxins.

Mesosome

Infoldings of the bacterial cell membrane that are involved in DNA replication and cell division.

Glycocalyx

The total of polysaccharide structures on the surface of bacteria, including capsules and slime layers.

Murein

Another term for peptidoglycan, which forms a crucial part of the bacterial cell wall.

Periplasmic Space

The space between the outer membrane and the cytoplasmic membrane in Gram-negative bacteria.

Teichoic Acids

Polymers typically found in the cell walls of Gram-positive bacteria, which play a role in cell viability.

Endospores

Dormant, tough, non-reproductive structures formed by some bacteria, aiding in survival under unfavorable conditions.

Chemical Fixation

A method of killing specimens and preparing them for staining using chemicals like ethanol or acetic acid.

Polar Flagella

Flagella that are located at one or both ends of the bacteria, enabling directed movement.

Simple Staining

A technique that uses a single stain to visualize the morphology and arrangement of bacteria.

Counterstain

A secondary stain used in differential staining procedures to provide contrast and enhance the visibility of the primary stain.

Mycolic Acids

Long-chain fatty acids found in the cell walls of certain bacteria, contributing to their hydrophobic nature.

Polysaccharides in Bacterial Cells

Storage compounds in bacteria that can include glycogen or other nutrients for energy.

Decolorization in Gram Staining

The critical step in the Gram staining process where a decolorizing agent is applied to differentiate Gram-positive and Gram-negative bacteria.