Overview
This lecture covers the classification of bacteria, key aspects of their anatomy, nutritional requirements, and patterns of bacterial growth.
Bacterial Classification
- Bacteria are classified by shape (cocci, bacilli, spirilla), staining (Gram-positive or Gram-negative), and oxygen need (aerobic or anaerobic).
- Further classification uses cell arrangement (chains, clusters) and biochemical tests.
Bacterial Anatomy
- All bacteria have a cell membrane, cytoplasm, ribosomes, and genetic material (DNA).
- The cell wall differs between Gram-positive (thick peptidoglycan) and Gram-negative (thin peptidoglycan, outer membrane) bacteria.
- Some bacteria have additional structures: flagella (movement), pili (attachment), capsules (protection).
Bacterial Nutrition
- Bacteria require sources of carbon, nitrogen, water, and minerals for growth.
- Classification by nutrition: autotrophs (make own food) and heterotrophs (use organic sources).
- Some bacteria are obligate parasites, needing a host for survival.
Bacterial Growth
- Growth occurs by binary fission, producing two identical cells.
- The bacterial growth curve has four phases: lag, log (exponential), stationary, and death.
- Growth rate is affected by temperature, pH, and nutrient availability.
Key Terms & Definitions
- Gram-positive — bacteria with thick peptidoglycan cell walls that retain crystal violet stain.
- Gram-negative — bacteria with thin peptidoglycan and an outer membrane; do not retain crystal violet stain.
- Binary fission — method of bacterial reproduction, splitting one cell into two.
- Autotroph — an organism that produces its own food from inorganic substances.
- Heterotroph — an organism that requires organic compounds for food.
Action Items / Next Steps
- Review bacterial shapes, staining, and growth curve phases.
- Read about bacterial nutrition and factors that affect growth.