The Carbon Cycle and Its Implications

Lecture 25: The Carbon Cycle

• The lecture covers an overview of the carbon cycle
• It details microbial involvement in the cycle
• Applications of the carbon cycle include waste water treatment and composting
• The lecture also discusses anoxic environments and methanogens and syntrophs.

Biosphere 2 Experiment

• The presentation addresses the "failed" Biosphere 2 experiment.
• Questions are raised regarding the factors that went wrong.

Carbon Cycle Diagram

• A diagram shows the various processes involved in the carbon cycle.
• The diagram displays the cyclical flow of carbon between different reservoirs on the planet.
• Processes like photosynthesis, respiration, volcanism, and the burning of fossil fuels are depicted.
• Feedback loops, like the greenhouse effect, are also shown.
• Areas of carbon storage are indicated.
• The diagram includes human activities that affect the cycle.

Bacteria's Role in the Carbon Cycle

• A study emphasizes the pivotal role bacteria play in global nutrient and carbon cycling in soil.
• The study particularly explores how bacteria impact soil nutrient movement.

Carbon Cycle – Overview

• The carbon cycle's major processes are explained.
• It outlines the processes of carbon fixation and decomposition.
• Aerobic and anaerobic respiration and their roles are described
• The diagram distinguishes between carbon fixation and respiration, which involves the use of carbon, and the release of carbon.

Carbon Fixation Pathways

• Different pathways for carbon fixation are discussed.
• These include the Calvin cycle, used by various organisms, such as plants and cyanobacteria.
• The cycle's steps are detailed, including those involving RuBisCo.

Net Carbon Gain and Loss

• The diagram differentiates between net carbon gain and net carbon loss.
• The processes that happen in either scenario, like photosynthetic carbon fixation and photorespiration, are illustrated.

Reverse TCA Cycle

• The presentation gives an overview of the reverse TCA cycle, a carbon fixation pathway involving green sulfur bacteria and other microorganisms.

Decomposition

• Decomposition processes break down dead biomass into simple compounds.
• Decomposition relies on chemo-organo-heterotrophs through different respiration pathways
• Secondary decomposers break down organic matter for primary microorganisms

Wastewater Treatment

• Wastewater treatment goals, from pathogen elimination to reducing biological oxygen demands, are presented.
• Different stages of treatment – primary, secondary, and tertiary – are outlined.
• Primary treatment involves physical methods like screening and sedimentation.
• Secondary treatment utilizes biological mechanisms such as activated sludge and anaerobic digestion.
• Tertiary treatment implements chemical methods like chlorination and UV treatment to further purify water.

Aeration's role in wastewater treatment

• Aeration of wastewater increases oxygen to enable different decomposition processes
• It improves anaerobic fermentation of organic compounds
• It facilitates aerobic respiration to break down organic matter
• It ensures that autotrophs can fix carbon dioxide during the Calvin cycle using aeration from the wastewater.

Anoxic Habitats

• The presentation identifies environments with low or no oxygen, like anaerobic digestions used in wastewater treatment.
• Examples of anoxic environments that contain microbial oxygen consumption are given.

Anaerobic Digestion and Methanogenesis

• The processes involve anaerobic respiration and methanogenesis which are crucial components of biogas.
• Methanogens are essential for creating methane.

Methanogens

• Processes where methanogens (archaea) produce methane using hydrogen and CO, or acetate, are described in detail.
• Details about methanogenesis processes are given, including the involved microbes and chemical reactions.

Syntrophic Relationships

• Methanogens and bacteria often display syntrophic relationships – a collaborative process that facilitates energetically unfavorable fermentation reactions.
• These reactions are favored by consuming hydrogen or acetate

Anaerobic Organic Matter Breakdown

• The breakdown of organic matter under anaerobic conditions involves multiple steps, with syntrophic relationships playing a major role.
• The various organisms (like acetogens and methanogens) and metabolic processes involved in breaking down organic matter are detailed.

This quiz explores the intricate details of the carbon cycle, including microbial interactions and applications in environmental management such as wastewater treatment and composting. It also examines notable experiments like Biosphere 2 and the crucial roles of bacteria in carbon processes. Visual representations of the carbon cycle further enhance understanding of its mechanisms and human impacts.