Lecture Notes: Deep-Sea Ocean Vents and Microbial Life

Overview

• Discussion of microbial life in oceans, particularly focusing on photosynthetic bacteria and other microorganisms in plankton.
• Importance of light energy utilization in aquatic environments.

Key Microorganisms

• Actinobacteria (AC1): Contains actinorhodopsin.
• Polygobacter ubique: Contains proteorhodopsin.
• Cyanobacteria: Also harness light energy.

Discovery and Energy Balance

• Discovery of rhodopsins helped balance the energy equations in oceanic ecosystems.

Deep-Sea Ocean Vents

• Exploration began in 1977 by geologists.
• Physical Environment:
  • Volcanic activity between tectonic plates.
  • Temperatures range from 5 to 400°C; close to vents 350°C.
  • Acidic to neutral pH.
  • Water absorbs chemicals like hydrogen sulfide, methane.
  • Over 500 known systems.

Energy Sources and Chemistry

• Electron Donors: Hydrogen, ammonia, hydrogen sulfide, methane.
• Electron Acceptors: Oxygen, nitrite, nitrate.

Microorganisms at Vents

• Sulfide Oxidizers: Convert hydrogen sulfide to sulfate.
• Methanogens: Produce methane using hydrogen gas and CO2.
• Methylotrophs: Oxidize methane to CO2 and water.
• Hydrogen Oxidizers: Use hydrogen to produce hydrogen sulfide.

Examples of Organisms

• Methanococcus jannaschii: Grows over 100°C.
• Pyridicium abyssii: Grows over 113°C, produces lattice structures.

Chemolithotrophic Reactions

• Example Organisms:
  • Geoglobus ahangari: Uses iron as an electron acceptor, grows chemoautotrophically on acetate.
  • Thermococcus atlanticus: An obligate anaerobe and thermophile that grows on proteinaceous substances.

Symbiotic Relationships

• Tube Worms: Symbiosis with bacteria that oxidize H2S and fix CO2.
  • Tube worms utilize a hemoglobin protein to uptake CO2 and H2S.
  • Bacteria provide organic matter to the worms.

The Carbon Cycle

• Origin of carbon from fusion in stars.
• Most carbon on Earth is inorganic and in rocks/sediments.
• Cycling through living systems involves conversion of CO2 and methane by microorganisms.

Autotrophic Pathways

• Calvin Cycle: Classic CO2 fixation in plants.
• Reductive Acetyl-CoA Pathway: Utilizes hydrogen and CO2 to produce acetyl-CoA with minimal ATP requirement.

Methylotrophs

• Oxidize methane for energy and carbon.
• Typically proteobacteria performing aerobic respiration.
• Methyl monooxygenase (MMO): Key enzyme in methane oxidation.

Global Carbon Cycle Impact

• Small net addition of carbon to the cycle can have significant effects.
• Microbes play crucial roles in respiration and photosynthesis.

Introduction to Immunity

• Overview of immune system functions, focusing on defense mechanisms against microorganisms.
• Common Misconception: Majority of immune system is not in circulatory system but associated with the gastrointestinal tract.
• Immune System Elements:
  • Physical barriers
  • Innate immunity (phagocytosis, inflammatory response)
  • Acquired immunity (antibody-mediated and cell-mediated responses)

Identification of Self vs. Non-Self

• Importance of differentiating between self and potential pathogens.
• Immune system creates lymphocytes responsive to macromolecules, eliminates those responsive to self.

These notes provide a detailed overview of the lecture's key topics, including microbial life in ocean environments, the unique ecosystems of deep-sea ocean vents, and an introduction to the immune system and its role in defending against microbial threats.