Gram-Positive vs. Gram-Negative Cell Walls and Related Antibiology

Vocabulary flashcards covering key terms related to Gram-positive and Gram-negative cell walls, their components, and associated antibiotics.

Gram-positive bacteria

Bacteria with thick (up to ~40 layers) peptidoglycan cell walls that retain the crystal-violet stain and appear purple after Gram staining.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer, an additional outer membrane, and lipopolysaccharide (LPS); appear pink/red after Gram staining.

Peptidoglycan

Rigid polymer of sugars and amino acids forming bacterial cell walls; thicker in Gram-positive cells and a key antibiotic target.

Gram stain

Differential staining technique that categorizes bacteria as Gram-positive (purple) or Gram-negative (pink/red) based on cell-wall structure.

Staphylococcus aureus

Common Gram-positive coccus; notable human pathogen frequently causing skin infections and other illnesses.

Streptococcus pyogenes

Gram-positive bacterium that causes strep throat and other infections; member of the Streptococcus genus.

Plasma membrane

Phospholipid bilayer surrounding the cytoplasm of all cells; lies beneath the cell wall in bacteria.

Outer membrane

Extra lipid bilayer found only in Gram-negative bacteria, external to the peptidoglycan layer, containing LPS.

Lipopolysaccharide (LPS)

Complex molecule in the outer membrane of Gram-negative bacteria; also called endotoxin.

Endotoxin

Toxic component (mainly LPS) released from Gram-negative bacteria that can trigger strong inflammatory responses and septic shock.

Septic shock

Severe, potentially fatal condition caused by widespread inflammation and low blood pressure, often due to high endotoxin levels.

Penicillin

β-lactam antibiotic that inhibits peptidoglycan synthesis; most effective against Gram-positive bacteria.

Vancomycin

Glycopeptide antibiotic that blocks peptidoglycan cross-linking; key treatment for resistant Gram-positive infections.

Cephalosporins

Family of β-lactam antibiotics with multiple generations; inhibit cell-wall synthesis and treat many Gram-positive infections.

Selective toxicity

Property of antimicrobial drugs to harm microbes without damaging host cells; possible because humans lack peptidoglycan.

Protein synthesis inhibitors

Antibiotics (e.g., aminoglycosides, tetracyclines) that block bacterial ribosomes; commonly used for Gram-negative infections.

DNA synthesis inhibitors

Antibiotics (e.g., fluoroquinolones) that disrupt bacterial DNA replication or transcription, useful against Gram-negative pathogens.