Microbial Physiology - Lec 1

Microbial Physiology - Lec 1

• Microbial physiology focuses on the relationship between structure and function in microorganisms, particularly how microbes respond to their environment.
• Microbial habitats, including soil, rivers, lakes, oceans, living/dead organisms, and human-made structures, provide nutrients and protect microbes from harsh conditions.
• Microbial physiology provides insights into energy sources and their utilization by microorganisms.
• Microbes play vital roles in the environment as producers, consumers, and decomposers. They are also important in industry, medicine, and agriculture.
• Microorganisms act like miniature factories producing enzymes and metabolites vital to various industries. Gene regulation and environmental factors influence the production of these metabolites.
• Primary metabolites (like amino acids and nucleotides) are essential for microbial growth, while secondary metabolites (antibiotics, antitumor agents, etc.) are not essential for growth but impactful for human health.

Bacterial Structure

• Bacteria are unicellular prokaryotic cells, differing in shape, size, and arrangement.
• Bacterial DNA is in the cytoplasm, not enclosed within a nucleus as in eukaryotic cells.
• Bacteria are significantly smaller than human cells (approx. 1µm in diameter).
• The cell wall, composed of peptidoglycan or murein, provides structural integrity to the bacteria.
• Bacteria may have external appendages like cilia and flagella.

Bacterial Shape

• Spherical (cocci):
  • Coccus (single sphere)
  • Diplococci (pairs)
  • Streptococci (chains)
  • Sarcinae (cubes of 8)
  • Tetrads (groups of 4)
  • Staphylococci (clusters)
• Rod-shaped (bacilli):
  • Bacillus (single rod)
  • Diplobacilli (pairs)
  • Streptobacilli (chains)
  • Palisades (rods arranged side-by-side)
  • Coccobacilli (short rods)
• Spiral/Helical:
  • Spirillum (rigid spiral)
  • Spirochete (flexible spiral)
• Comma-shaped (vibrio): Curved, like a comma.

Gram-Positive vs. Gram-Negative Bacteria

• Gram-positive:
  • Lack an outer membrane
  • Have a thick peptidoglycan cell wall
  • Often spherical or rod-shaped
  • Produce toxins (e.g., emetic, diarrheal) causing disease
• Gram-negative:
  • Have an outer membrane and a thin peptidoglycan layer
  • Often spherical, rod-shaped, or spiral-shaped
  • Can release endotoxins if cell wall is disrupted
• Differences in cell wall structures affect staining/classification and pathogenesis.

Other Bacterial Arrangements

• Tetrads: Four bacteria arranged in a cluster
• Staphylococci: Clusters of bacteria
• Sarcinae: Eight bacteria arranged in a three-dimensional cube structure.

Additional points

• Microbes degrade various carbon sources aerobically and anaerobically yielding commercially valuable metabolites.
• The course syllabus is designed to reflect recent advancements in microbial physiology.