Bacterial Structure and Morphology

The outer layer of a bacterial cell that provides structural support and protection.

A thick layer of peptidoglycan found in the cell walls of Gram-positive bacteria.

A thin layer of peptidoglycan found in the cell walls of Gram-negative bacteria.

Repeating units of N-acetylmuramic acid (NAMA) and N-acetyl glucosamine (NAGA) linked by beta 1,4-glycosidic bonds, forming the backbone of peptidoglycan.

A bond connecting the sugars in the glycan chain of peptidoglycan. It is the target of lysozyme.

An enzyme found in human tears, saliva, and mucus that breaks down the glycosidic bonds in peptidoglycan, weakening bacterial cell walls.

A component of the Gram-positive bacterial cell wall that strengthens the peptidoglycan layer.

The ability of an organism to resist infection.

A complex molecule composed of three parts: lipid A, core polysaccharide, and outer polysaccharide. It's found in the outer membrane of Gram-negative bacteria.

A phospholipid component of LPS that is responsible for its toxic effects. It can trigger a powerful immune response, leading to septic shock.

A polysaccharide chain attached to lipid A, forming the middle layer of LPS, providing structure and contributing to the overall complexity of the molecule.

A complex carbohydrate chain composed of repeating sugar units, extending from the core polysaccharide. It functions as the O antigen, a key identifier for specific Gram-negative bacteria.

A type of protein channel found in the outer membrane of Gram-negative bacteria, allowing the passage of certain molecules.

A unique cell wall characteristic of Mycobacteria, like Mycobacterium tuberculosis. They are resistant to decolorization by acid-alcohol after staining, due to a high concentration of mycolic acids.

A specialized type of lipid found in high concentrations in the cell walls of mycobacteria, responsible for their acid-fast characteristic.

Bacterial strains that lack a cell wall. They can survive in specific conditions, but are vulnerable to external threats.

A bacterial enzyme involved in peptidoglycan synthesis. It catalyzes the formation of peptide cross-links between peptidoglycan chains, strengthening the cell wall.

A group of proteins in bacterial cell walls that are essential for peptidoglycan synthesis. They are the primary targets of beta-lactam antibiotics like penicillin.

Beta-lactam antibiotics like penicillin bind to the active site of transpeptidases, preventing them from cross-linking peptidoglycan chains. This inhibits cell wall synthesis and ultimately leads to bacterial death.

A type of bacterial cell wall that is thicker and contains a large amount of peptidoglycan. Gram-positive bacteria are typically more susceptible to penicillin than gram-negative bacteria.

A type of bacterial cell wall that is thinner and contains less peptidoglycan compared to gram-positive bacteria. It also has an outer membrane.

A component of the gram-negative bacterial cell wall. It is embedded in the outer membrane and is responsible for many of the disease symptoms caused by these bacteria.

A condition characterized by inflammation and organ dysfunction caused by the release of inflammatory mediators in response to bacteria, especially gram-positive bacteria. Teichoic acids play a role in triggering septic shock.

An inward fold of the cytoplasmic membrane, significant for cell division as it forms the transverse septum that divides the cell in half and acts as the attachment point for the DNA destined for each new cell.

The jelly-like substance within a bacterial cell, containing ribosomes, nutrient granules, metabolites, and plasmids. It is divided into two parts: the amorphous matrix and the nucleoid.

The cellular structures responsible for protein synthesis. Bacterial ribosomes are smaller than eukaryotic ribosomes (70S vs 80S) and have different subunits (50S and 30S vs 60S and 40S).

Small, circular DNA molecules found in bacterial cells that can replicate independently of the main chromosome.

The region in the cytoplasm where the bacterial DNA is located. It is distinct from the eukaryotic nucleus and lacks the nuclear membrane, nucleolus, mitotic spindle, and histones.

Storage units within the cytoplasm that hold nutrients and stain uniquely with specific dyes.

The single, circular DNA molecule that carries the bacterial genome. It is much smaller than eukaryotic DNA and lacks introns.

Differences in the ribosomal RNA and proteins of bacteria and eukaryotes allow for selective action of antibiotics that inhibit bacterial protein synthesis without affecting human cells.

Plasmids that can be transferred from one bacterium to another through conjugation.

Plasmids that cannot be transferred between bacteria.

Genes carried by plasmids that provide resistance to antibiotics, heavy metals, or other harmful substances.

Pieces of DNA that can move from one location to another in the genome, including between bacteria, plasmids, and viruses.

A protective outer layer found in some bacteria that helps them evade the immune system and survive.

Hair-like protein structures on the surface of bacteria that allow them to attach to surfaces or other cells.

A layer of sugars and proteins on the surface of some bacteria that helps them form biofilms.

A layer composed of polysaccharides (sugars) surrounding some bacteria.

The capsule's composition varies among bacteria, determining serologic types. For example, there are 84 different serologic types of Streptococcus pneumoniae.

The capsule hinders phagocytes from engulfing bacteria, contributing to their virulence (ability to cause disease).

In the presence of the homologous antibody (specific to the capsule), the capsule will swell greatly, a reaction called the Quellung reaction.

Capsular polysaccharides are used as antigens in some vaccines.

The capsule may facilitate bacteria's adherence to human tissues during infection. This is a crucial step in causing disease.

Long, whip-like appendages that enable bacteria to move towards nutrients or attractants. This movement is called chemotaxis.

The number and location of flagella vary between bacteria. Some have one, others have many. They can be at one end or spread across the surface. Not all bacteria have flagella.