Notes on Microbial Diversity and Metabolism

Microbial Diversity II

Announcements

• No class on Thursday, April 10
• Recorded lecture on fungi posted to Canvas
• Office hours on Monday, April 14 cancelled

Elements of Metabolism

• Energy Production: Organisms produce ATP as a primary energy currency.
  • Key Roles:
    • Energy production (ATP)
    • Building material (carbon)

Bacteria and Archaea Metabolic Modes

• Table 27.1 Overview of Major Nutritional Modes:
  • Autotrophs:
    • Photoautotroph:
      • Energy Source: Light
      • Carbon Source: CO2, HCO3, or related compound
      • Examples: Prokaryotes (like cyanobacteria), plants, certain protists (like algae)
    • Chemoautotroph:
      • Energy Source: Inorganic chemicals (e.g., H2S, NH3, Fe²+)
      • Carbon Source: CO2
      • Examples: Unique to certain prokaryotes (e.g., Sulfolobus)
  • Heterotrophs:
    • Photoheterotroph:
      • Energy Source: Light
      • Carbon Source: Organic compounds
      • Examples: Unique to certain aquatic and salt-loving prokaryotes
    • Chemoheterotroph:
      • Energy Source: Organic compounds
      • Examples: Many prokaryotes (e.g., Clostridium), fungi, animals, some plants

Microcystis viridis (Phylum Cyanobacterium)

• Metabolic Characteristics:
  • Type: Photoautotrophic
  • Energy Production: Captures light energy to produce ATP
  • Organic Compounds Synthesis:
    • Uses energy from light for CO2 metabolism
  • Historical Contribution: Significant oxygen producer during Proterozoic era, forming stromatolites

Metabolic Cooperation in Cyanobacteria

• Nitrogen Fixation:
  • Converts atmospheric N2 to NH3, allowing incorporation into proteins
  • Nitrogen-fixing enzymes are inhibited by the presence of oxygen

Nitrobacter vulgaris

• Metabolic Strategy:
  • Consumes nitrites (NO2-) as energy source
  • Cannot survive without CO2
  • Converts nitrites into nitrates (NO3-) as waste
  • Plays a critical role in the nitrogen cycle

The Nitrogen Cycle

• Processes Involved:
  • Nitrogen Fixation: Bacteria and archaea convert atmospheric N2 into NO3.
  • Reduction: Bacteria/archaea break down NO3 into components usable by plants.
  • Decomposition: Organic compounds with amino groups (-NH2) are returned to the environment.

Role of Legumes in Nitrogen Fixation

• Examples: Beans, lentils, alfalfa, peanuts.
• Key Features:
  • Roots contain nodules housing symbiotic bacteria that fix nitrogen for plant use (mutualism).

Heliobacillus mobilis

• Characteristics:
  • Photosynthetic but does not produce oxygen.
  • Cannot synthesize organic compounds from CO2; instead, ingests organic acids (acetate, pyruvate).
  • Type: Obligate anaerobe

Desulfonauticus submarinus

• Energy Production: Generates ATP through the reduction of sulfur or hydrogen sulfide, forming the basis for hydrothermal vent communities

Alcanivorax borkumensis

• Metabolic Strategy: Utilizes hydrocarbons as both an energy and carbon source.
• Ecological Role: Notable for its application in bioremediation to clean up oil spills.