Medical Microbiology Midterm REVIEW

Prokaryotic vs Eukaryotic Cells

• Definition: Prokaryotic cells are simple, single-celled organisms without a nucleus. Eukaryotic cells have a defined nucleus and are usually more complex and larger.

• Examples: Prokaryotes include bacteria and archaea; eukaryotes include fungi, plants, and animals.

• Reproduction: Prokaryotes reproduce by splitting into two (binary fission), while eukaryotes can reproduce in more ways, including sexual reproduction.

Shapes of Bacteria and Nomenclature

• Bacteria can come in different shapes:

  • Cocci: round (spherical)

  • Bacilli: rod-shaped

  • Spirilla: spiral-shaped

• Names can include how they group together, like clumps (staphylococci) or chains (streptococci).

Gram-Positive vs Gram-Negative Bacteria

• Gram-positive: Thick peptidoglycan layer, stains purple during testing.

• Gram-negative: Thin peptidoglycan layer, double membrane, stains pink.

• General Similarities/Differences: Both types have cell walls and a cell membrane, but they differ in structure and how they react to antibiotics.

Phospholipid Membrane Properties

• Made of two layers of phospholipids, which allows some things to pass through while blocking others.

• Transport: Molecules can move across the membrane through different methods, including passive movement and active transport, which requires energy.

Gram-Staining Technique

• A method to color bacteria using several steps: first apply crystal violet, then iodine, rinse with alcohol, and finally use a counterstain (safranin). This helps identify bacteria based on their cell wall structure.

Cell Wall Structure

• Characteristics: Essential for maintaining the shape of bacteria and protecting them.

• Function: Gives strength and supports the bacteria against harsh conditions.

Composition of Bacterial Structure

• Includes basic parts like cytoplasm, ribosomes (making proteins), and the nucleoid (where DNA is located).

Chemical Make-up of Peptidoglycan

• Components: Made of sugars and peptide chains that provide support.

• Biosynthesis: The process of making peptidoglycan involves linking these sugars and peptides together, critical for the bacterium's strength.

Bacterial Membrane Components

• Gram-positive: Contains substances like teichoic acids.

• Gram-negative: Includes lipopolysaccharides (LPS) and proteins that form channels for nutrient flow.

Bacterial Spores

• Spores are highly resistant forms of bacteria that can survive extreme conditions like heat and dryness. Important for the survival and spread of certain types of bacteria.

Bacterial Metabolism

• Aerobic: Needs oxygen for energy (e.g., Mycobacterium).

• Anaerobic: Can live without oxygen (e.g., Clostridium).

• Facultative: Can grow with or without oxygen (e.g., E. coli).

Genetic Exchange in Bacteria

• Bacteria can share genes through several methods:

  • Transformation: Taking up DNA from the environment.

  • Transduction: Virus-mediated transfer of DNA.

  • Conjugation: Direct transfer of DNA between two bacteria.

Bacterial Infection and Virulence Factors

• Virulence Factors: Features that allow bacteria to cause disease include adhesion proteins (adhesins) and toxins. Biofilms can help bacteria stick to surfaces and resist treatment.

Toxins in Bacteria

• Exotoxins: Harmful proteins released into the environment (e.g., diphtheria toxin, cholera toxin).

• Endotoxins: Part of the bacterial cell wall (like LPS) that can trigger inflammation when bacteria get into the body.

• Antibiotics: Medicines that kill or stop bacteria, often targeting their cell wall or protein production. Misuse can lead to resistant bacteria.