Bacterial Morphology and Classification

Bacterial Morphology and Classification

• Bacteria are classified based on their Gram stain reaction (Gram-positive or Gram-negative)
• Gram-positive bacteria stain purple, while Gram-negative stain pink
• Gram-positive cell walls have a thick peptidoglycan layer
• Gram-negative cell walls have a thin peptidoglycan layer and an outer membrane

Bacterial Staining

• Gram staining is a differential staining technique used to distinguish between Gram-positive and Gram-negative bacteria
• Crystal violet is used as the primary stain
• Iodine is used as the mordant
• Decolorizer (alcohol or acetone) removes the crystal violet from Gram-negative bacteria
• Safranin is used as the counterstain to stain Gram-negative bacteria pink

Bacterial Structure

• Bacterial cells have a cell wall, which provides structural support
• Some bacterial cells have a capsule, which protects the cell from the host's immune system
• Flagella are used for movement
• Pili are used for attachment

Bacterial Reproduction

• Bacteria reproduce by binary fission
• Some bacteria can form endospores, which are dormant structures that can survive harsh conditions

Bacterial Pathogenicity

• Some bacteria cause diseases in humans and animals
• Pathogenic bacteria can produce toxins that damage host tissues
• Pathogenic bacteria can cause infections by invading tissues and producing toxins

Bacterial Metabolism

• Some bacteria are aerobic, meaning they require oxygen to survive
• Some bacteria are anaerobic, meaning they do not require oxygen to survive
• Some bacteria are facultative anaerobes, meaning they can survive with or without oxygen

Specific Bacterial Examples

• Escherichia coli is a Gram-negative bacterium commonly found in the gut
• Salmonella is a Gram-negative bacterium that can cause food poisoning
• Bacillus anthracis is a Gram-positive bacterium that causes anthrax
• Neisseria gonorrhoeae is a Gram-negative bacterium that causes gonorrhea
• Borrelia burgdorferi is a spirochete that causes Lyme disease

Bacterial Identification Techniques

• Techniques such as Gram staining aid in preliminary identification
• Biochemical tests can further characterize bacteria and help pinpoint the species
• Serological tests, such as ELISA or agglutination tests, can identify specific antigens for particular species

Bacterial Diseases

• The different species of bacteria cause different diseases (eg, Anthrax, Gonorrhea, Lyme disease)