Lecture Notes: Microbial Metabolism

Overview

• Microbial metabolism refers to the biochemical reactions necessary for life in microorganisms.
• Includes two main processes:
  • Catabolism: Process by which organisms obtain energy.
  • Anabolism: Process of building macromolecules, discussed later in the chapter.

Types of Metabolism

• Most organisms utilize one type of metabolism.
• Some organisms adapt and use different energy sources based on environmental conditions.

Energy Sources

• Defined as either chemical or light (photon) energy sources.

Chemical Energy Sources: Chemotrophs

• "Trophy" means to nourish.
• Further classified based on chemical type:
  • Chemo-organotrophs: Use organic chemicals like glucose.
    • Example: E. coli.
  • Chemolithotrophs: Use inorganic chemicals, e.g., hydrogen gas.
    • "Litho" means stone-like.
    • Example: Theobacillus theo-oxidans.
  • Both types are involved in making ATP and other energy molecules.

Light Energy Sources: Phototrophs

• Contain pigments to utilize photons as energy.
• Example: Rhodobacter capsulatus.

Carbon Sources

• Cells require carbon for growth, which can be obtained in two ways:

Heterotrophs

• Obtain carbon from organic sources.

Autotrophs

• Use carbon dioxide as a carbon source (inorganic).

Combined Metabolic Types

• Chemolithoautotrophs: Most chemolithotrophs and phototrophs are autotrophs.
• Chemoorganoheterotrophs: Most chemoorganotrophs are heterotrophs.