LQB362_Lecture_Week_2_25se1_All

Introduction

• Overview of lecture topic: Bacterial cell structure and cultivation of bacteria.

• Facilitator: Dr. Eva Hatje.

• Course: LQB362 Fundamentals of Microbiology.

• TEQSA Provider ID: PRV12079.

• Acknowledgment of traditional owners: Turrbal and Yugara.

Learning Outcomes

1. Structure and function of bacterial cytoplasm and plasma membrane.

2. Bacterial cell wall structures: Gram positive, Gram negative, acid-fast bacteria, with examples of medically important bacteria.

3. Identification of bacterial cell surface features and their functions.

4. Nutritional and physical conditions necessary for microbial growth.

5. Bacterial metabolism: aerobic and anaerobic respiration, and fermentation processes.

6. Differences between complex, defined, enriched, differential, and selective media.

Bacterial Cell Structure

• Bacterial cell wall made of peptidoglycan (murein):

  • Provides shape and rigidity.

  • Distinction between Gram positive and Gram negative bacteria.

• Gram Positive Bacteria:

  • Contains teichoic acids.

• Gram Negative Bacteria:

  • Has an additional outer membrane with lipopolysaccharides (LPS).

  • Porins allow transport across the outer membrane.

Cytoplasm and Organelles

• Composition: 80% water, 20% carbohydrates, proteins, lipids, salts.

• Key organelles:

  • Nucleoid: Houses DNA (single circular chromosome).

  • Plasmids: Small circular DNA (not essential, varies by species).

  • Ribosomes: Protein synthesis.

  • Inclusion bodies: Storage of nutrients or energy.

  • Endospores: Survival structures, formed in harsh conditions.

Transport Mechanisms Across Membrane

Passive Transport

• Requires no energy, moves with concentration gradient:

  • Simple diffusion, facilitated diffusion (channel/carrier proteins), osmosis.

Active Transport

• Requires energy for transport against gradients:

  • Symport, antiport, ABC transport, group translocation (unique to prokaryotes).

Nutritional Requirements for Growth

• Physical Requirements: Temperature, pH, osmotic pressure.

• Chemical Requirements:

  • Oxygen (various requirements based on species), vital nutrients like carbon, nitrogen, sulfur, phosphorous.

• Example: Helicobacter pylori - causes gastric ulcers; notable for specific nutritional and environmental requirements.

Bacterial Metabolism

• Metabolism: Sum of chemical reactions; comprises:

  • Catabolic (energy-releasing) and anabolic (energy-using) pathways.

• Energy extraction from glucose via:

  • Cellular respiration (aerobic and anaerobic) and fermentation.

• Pathways: Glycolysis, Krebs cycle, electron transport chain, pentose-phosphate pathway.

Culture Media Types

• Types: Complex, defined, enriched, selective, and differential media.

• Examples:

  • Nutrient agar (complex), blood agar (enriched), MacConkey agar (selective and differential).

• Importance of media in microbial growth, examples of pathogens and their culture requirements.