LQB362+Lecture+Week+2_25se1_All

Introduction to Microbiology

• Course Details: LQB362 - Fundamentals of Microbiology, Dr. Eva Hatje, School of Biomedical Sciences, QUT

• Contact: e.hatje@qut.edu.au

Acknowledgement of Country

• QUT acknowledges the Turrbal and Yugara peoples as the traditional owners of the land. Respect is paid to their Elders, customs, and teachings.

Textbooks for Study

• Tortora, G. J., Funke, B. R., & Case, C. L. (2021). Microbiology: An Introduction (Thirteenth Edition).

  • Chapters: 4, 5, 6

• Madigan, M. T., et al. (2022). Brock Biology of Microorganisms (Sixteenth Edition).

  • Chapters: 2, 3, 5

Learning Outcomes

1. Structure and function of bacterial cytoplasm and plasma membrane; transport mechanisms.

2. Cell wall structure, comparison of Gram-positive, Gram-negative, and acid-fast bacteria; examples of medically important bacteria.

3. Identification of bacterial surface features and their functions; examples in medical context.

4. Nutritional and physical conditions for microbial growth; terminology for growth environments.

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

6. Distinctions among complex, defined, enriched, differential, and selective media with examples.

Cell Structure Overview

• Plasma Membrane: A phospholipid bilayer with embedded proteins. In Gram-negative bacteria, there is an inner and outer membrane.

  • Fluid Mosaic Model: Describes the arrangement and movement of phospholipids and proteins in membranes.

• Functions: Selectively permeable barrier controlling substances entering and exiting the cell.

Transport Mechanisms

Passive Transport

• No energy required; relies on concentration gradients.

  1. Simple Diffusion: Movement of small or nonpolar molecules.

  2. Facilitated Diffusion: Uses channel or carrier proteins for larger or polar molecules.

  3. Osmosis: Diffusion of water across a selectively permeable membrane.

Active Transport

• Requires energy (ATP); transports molecules against concentration gradients.

  1. Simple Transport: Includes symport and antiport processes.

  2. ABC Transport: Involves ATP-binding cassette transport systems.

  3. Group Translocation: A unique prokaryotic process where the substance is chemically altered during transport.

Cytoplasm and Its Components

• Mostly water (~80%), containing carbohydrates, proteins, lipids, and salts.

• Nucleoid: Contains the bacterial chromosome (single circular DNA).

• Plasmid: Small, extra-chromosomal DNA molecules.

• Ribosomes: Site of protein synthesis.

• Inclusions: Storage entities for nutrients or gases (e.g., gas vesicles, magnetosomes).

Endospores

• Specialized survival structures formed in harsh conditions (e.g., heat).

• Notable Examples: Bacillus and Clostridium species.

Bacterial Cell Wall

Structure

• Composed mainly of peptidoglycan (murein); provides structural integrity.

Types of Cell Walls

1. Gram-positive: Thick layer of peptidoglycan, contains teichoic acids.

2. Gram-negative: Thin peptidoglycan layer surrounded by an outer membrane with lipopolysaccharides (LPS).

3. Acid-Fast: Waxy cell wall containing mycolic acid.

Medically Relevant Bacteria

• Gram-positive: Staphylococcus aureus; causes toxic shock syndrome and other infections.

• Gram-negative: Escherichia coli; commonly involved in gastrointestinal infections.

• Acid-fast: Mycobacterium tuberculosis; causes tuberculosis.

• Mycoplasma: Lack cell walls, causes lung infections (e.g., Mycoplasma pneumoniae).

Nutritional Requirements

• Physical: Temperature, pH, osmotic pressure.

• Chemical: Oxygen needs vary by species; include major nutrients like carbon, nitrogen, sulfur, and trace elements.

Culturing Methods

Types of Media

• Complex Media: Exact composition unknown, supports a wide variety of microorganisms.

• Defined Media: All chemical components are known.

• Selective Media: Inhibits unwanted organisms while allowing desired organisms to grow.

• Differential Media: Contains indicators to distinguish different species based on biochemical characteristics.

Examples

• Nutrient Agar: Supports general bacterial growth.

• Blood Agar: Enrichment media for fastidious organisms.

• MacConkey Agar: Differential and selective; distinguishes Gram-negative bacteria based on lactose fermentation.

Bacterial Metabolism

• Definitions: Sum of all biochemical reactions within bacteria.

• Energy Production: Utilizes glycolysis, Krebs cycle, and electron transport chain for ATP generation.

Respiration and Fermentation

• Aerobic Respiration: Oxygen is the final electron acceptor.

• Anaerobic Respiration: Uses alternative electron acceptors like nitrate or sulfate.

• Fermentation: Organic molecules serve as electron acceptors, yielding products like lactic acid or ethanol.

Conclusion

• Understanding bacterial structure, growth conditions, and metabolism is essential for their study and management in healthcare and microbiology.