Chapter 16: Microbial Life - Microorganisms

Introduction to Microorganisms

• Microorganisms are tiny entities that cannot be seen with the naked eye.
• They include bacteria, protists, fungi, etc.
• A microscope is required to observe them.

Prokaryotes

• Prokaryotes, including bacteria, are very small organisms without a defined nucleus.
• They have significant biomass and are found everywhere on Earth.
• Can survive extreme conditions such as cold, hot, salty, acidic, or alkaline environments.
• Some bacteria are pathogens and can cause diseases, but most are benign or beneficial.
• Bacteria decompose dead organic matter, releasing nutrients back into the ecosystem.

Types of Bacteria

1. Cocci:
   • Spherical shape.
   • Can stick together to form chains e.g., streptococcus.
2. Bacilli:
   • Rod-shaped bacteria.
3. Spirilla:
   • Spiral-shaped bacteria.
   • Very long and flexible.

Gram Staining

• A method to differentiate bacteria:
  • Gram-positive: Retain purple dye due to thick peptidoglycan layer.
  • Gram-negative: Appear pink due to thin peptidoglycan layer.
• Important for identifying bacteria type and selecting appropriate antibiotics.

Bacterial Structures

• Capsule: Sticky layer outside some bacteria, aiding protection and attachment.
• Flagella and Pili: Structures aiding in movement and attachment to surfaces.

Reproduction and Adaptation

• Bacteria reproduce asexually through binary fission.
• Some bacteria can form endospores to survive extreme conditions.
• Bacteria exhibit nutritional diversity and can be classified based on energy and carbon sources:
  • Photoautotrophs: Use light for energy and CO2 for carbon.
  • Chemoautotrophs: Use chemicals for energy and CO2 for carbon.
  • Photoheterotrophs: Use light for energy and organic compounds for carbon.
  • Chemoheterotrophs: Use organic compounds for both energy and carbon (e.g., humans).

Biofilms

• Organized colonies of bacteria that adhere to surfaces.
• Can be difficult to remove due to their sticky nature.

Bioremediation

• The use of organisms, like bacteria, to clean up pollutants from soil, air, or water.

Archaea

• Prokaryotes similar to bacteria but can survive in extreme environments.
• Examples include methanogens that produce methane gas in anaerobic conditions.

Eukaryotes vs. Prokaryotes

• Prokaryotes lack a nucleus and membrane-covered organelles, unlike eukaryotes.

Types of Bacteria (Continued)

1. Proteobacteria: Gram-negative, diverse group.
2. Cyanobacteria: Photosynthetic bacteria that can fix nitrogen.
3. Chlamydias: Pathogenic bacteria living inside animal cells.
4. Spirochetes: Spiral-shaped bacteria causing diseases like syphilis.

Protists

• Mostly unicellular eukaryotes.
• Include algae (photosynthetic) and protozoans (heterotrophic).
• Types include:
  • Plant-like Protists: Algae conducting photosynthesis.
  • Animal-like Protists: Protozoans consuming other organisms.
  • Fungus-like Protists: Decomposers or parasites.
  • Mixotrophs: Can photosynthesize and consume other organisms.

Importance of Studying Microbial Life

• Understanding bacteria and protists is crucial for medical, environmental, and evolutionary studies.
• Practical applications in medicine, biotechnology, and environmental cleanup.