Gram Positive vs Gram Negative Bacteria Quiz

The Golden Age of Microbiology (1857-1914)

• Rudolf Virchow (1858) proposed the concept of biogenesis
• Louise Pasteur (1861) discovered the role of microorganisms in fermentation and developed the process of pasteurization
• The germ theory of disease was developed during this period

Key Microbiologists and Their Contributions

• Robert Koch (1876) developed the golden streak method and isolated the bacteria that cause tuberculosis and cholera
• Edward Jenner developed the concept of vaccination
• Alexander Fleming discovered the first antibiotic, penicillin, and Paul Ehrlich developed the first synthetic drug, "magic bullet"

Microscopy and Staining

• Objective lens: used to hold the stain or coat the specimen to enlarge it
• Mordant: used to hold the stain
• Stains: Malachite green, crystal violet, methylene blue, safranin, and carbolfuchsin

Gram Staining

• The Gram stain classifies bacteria into Gram-positive and Gram-negative
• Gram-positive bacteria tend to be killed by penicillin and detergents, while Gram-negative bacteria are more resistant to antibiotics
• The process of Gram staining involves primary stain, mordant, decolorizing agent, and counterstain
• Gram-positive bacteria retain the dark violet/purple color, while Gram-negative bacteria lose the color and appear pink

Characteristics of Bacteria

• Size, shape, and arrangement of bacterial cells: rod-shaped, diplobacilli, streptobacilli, coccobacilli, spiral, vibrios, and spirochetes
• Structures: glycocalyx, flagella, axial filaments, fimbriae, and pili

Cell Walls and Membranes

• Gram-positive cell walls: thick, rigid, and composed of many layers of peptidoglycan
• Gram-negative cell walls: thin, flexible, and composed of one or a few layers of peptidoglycan and an outer membrane
• Atypical cell walls: acid-fast cell walls contain high concentrations of mycolic acid and prevent the uptake of dyes

Plasma Membrane

• Thin structure lying inside the cell wall and enclosing the cytoplasm of the cell
• Consists primarily of phospholipids
• Functions as a selective barrier and is involved in antimicrobial activity
• Movement of materials across the membrane: passive processes (diffusion, osmosis) and active processes (active transport)

Cytoplasm

• Substance of the cell inside the plasma membrane
• Composition: 80% water, with ribosomes, nuclear area, and other components
• Functions: protein synthesis, DNA replication, and metabolic processes

Endospores

• Highly durable, dehydrated cells with thick walls and additional layers that form when essential nutrients are depleted
• Found in Gram-positive bacteria (genera Clostridium and Bacillus) and Gram-negative bacteria (Thermoactinomyces vulgaris)