Microbiology Lecture 6: Bacterial Physiology

Bacterial Physiology and Metabolic Diversity

• Lecture 6 in a Microbiology course
• Focuses on bacterial physiology and the variety of metabolic processes they utilize.

Lecture 5

• Covers microbial growth and bacterial physiology
• Describes how bacteria reproduce through binary fission
• Explores bacterial growth on solid and liquid media
• Outlines the growth phases observed in liquid bacterial cultures
• Explains methods for measuring bacterial growth (direct and indirect) and growth requirements.

Learning Outcomes

• Covers metabolic diversity
• Details the chemical basis of energy production
• Explains a simplified model of energy production
• Discusses energy storage and release methods in bacteria
• Differentiates between phototrophs and chemotrophs
• Further divides chemotrophs into chemoorganotrophs and chemolithotrophs
• Defines autotrophs and heterotrophs
• Mentions photosynthesis

Carbon and Energy

• All cells require carbon and energy for metabolic processes
• Bacteria have diverse methods of obtaining carbon and energy
• This diversity allows microbes to inhabit extreme environments.

Detailed Metabolic Classification (Diagram)

• Diagram shows a hierarchical classification of organisms based on their energy and carbon sources
• Classifies organisms as chemoautotrophs and photoautotrophs, and chemoheterotrophs, photoheterotrophs
• Distinguishes between oxygenic and anoxygenic photosynthesis
• Lists specific groups of bacteria for each metabolic pathway illustrated
• Shows the final electron acceptor, and how it relates to each pathway
• Includes examples of different types of bacteria along with their energy requirements

Molecular Plant

• Discusses the positive effects of microbes on plant health and growth
• Includes discussions of induced systemic resistance, root immune suppression, improved root architecture, microbiome recruitment, nutrient cycling, pathogen control, soil fungistasis, and soil remediation.

Chemical Basis of Energy Production

• Describes chemical reactions to generate energy
• Emphasizes the release of electrons during chemical reactions
• Explains electron energy storage
• Defines oxidation (loss of electrons) and reduction (gain of electrons)
• Outlines how stored energy in electrons is utilized or transferred
• Explains the role of ATP in the process

Simplified Model of Energy Production

• Illustrates a simplified model depicting the generation of ATP as the final product in a reaction chain
• Shows how light energy and glucose are converted into ATP
• Highlights the roles of enzymes in the process

Energy Storage

• Explains how organisms trap energy released via chemical reactions
• Describes how energy is stored as a high-energy phosphate bond in the molecule ATP
• Defines ADP (adenosine diphosphate) and provides insight into its function in the context of energy storage within cells

Energy Release

• Explains how cells access stored energy through enzymatic removal of phosphate groups from ATP
• Highlights the use of ATP as the main energy currency for cellular activities

How to Get Energy

• Breaks down mechanisms for energy acquisition
• Categorizes organisms as phototrophs (light energy) and chemotrophs (chemical energy)
• Further categorizes chemotrophs into chemoorganotrophs (organic sources) and chemolithotrophs (inorganic sources)

Chemoorganotrophs

• Describe how chemoorganotrophs derive energy from organic chemicals
• Explains how organic compounds are broken down to produce ATP
• Illustrates the variety of organic compounds used as energy sources

Aerobes, Anaerobes, Facultative Anaerobes

• Defines aerobes (requiring oxygen for energy production)
• Defines anaerobes (producing energy without oxygen)
• Defines facultative anaerobes (producing energy with or without oxygen)

Methanogens

• Discusses the role of methanogens in livestock digestive processes
• Explains how feed additives can affect methane production
• Identifies ruminant livestock as a significant source of methane emissions

Supplements (for reducing Methane)

• Details methane-reducing feed additives and supplements inhibiting methanogens in the rumen, resulting in a reduction of enteric methane emissions
• Explains when these additives/supplements are most effective and in what types of livestock.

Reducing Methane

• Discusses various methods for reducing methane, including synthetic chemicals, natural compounds (such as tannins and seaweed), and fats and oils.
• Provides an example of a feed source, such as seaweed, that has proven effective in reducing methane emissions from cattle.

Active Inhibitors (for Reducing Methane)

• Discusses specific compounds such as trihalomethanes (e.g. bromoform), as active ingredients in feed additives effective at decreasing methane emissions.
• Include Tannins as another example.

Benefits (of reducing methane emissions in livestock)

• Details improved efficiency in feed utilisation as a result of reduced methane formation
• Explains methane emissions as gross energy loss from feed intake, representing approximately 10%
• Highlights the potential benefits of reduced emissions

Chemolithotrophs

• Explains that chemolithotrophs obtain energy from inorganic chemicals
• Defines inorganic compounds (not containing carbon), such as H₂, H₂S, and Fe²⁺
• Details how oxidation reactions liberate electrons used in ATP synthesis
• Emphasizes that all cells require carbon as a major nutrient, regardless of their initial energy source

Chemolithotrophs (Examples and Table)

• Presentation illustrates various types of chemolithotrophic bacteria and their corresponding energy sources and respiration electron acceptors
• Provides examples and table showing different chemolithotrophic bacteria, their energy sources (inorganic compounds), and the electron acceptor during respiration

Heterotrophs and Autotrophs

• Defines heterotrophs as microbial cells utilizing organic compounds for carbon
• Defines autotrophs as microbial cells using CO₂ for carbon source
• Describes the fixation or Calvin cycle as part of the autotrophic process

Autotrophs

• Explains autotrophs as primary producers generating organic matter from atmospheric CO₂
• Explains that chemoorganotrophs and other organisms consume the organic material or waste products of autotrophs
• Highlights that all organic matter is derived from the initial CO₂ fixation and synthesis carried out by autotrophs.

Phototrophs

• Defines phototrophs as organisms using light as an energy source
• Explains that phototrophic pigments allow utilization of light for energy production
• Notes the pigments also provide color to cells

Photosynthesis

• Explains the process of photosynthesis, describing the reactions where ATP is generated
• Differentiates between oxygenic and anoxygenic photosynthesis
• Notes that oxygenic photosynthesis produces oxygen as a by-product, while anoxygenic photosynthesis does not.

Pigments in Phototrophic Cells

• Identifies chlorophylls and carotenoids as pigments in phototrophic cells
• Shows that photosynthetic pigments absorb a large portion of the electromagnetic spectrum
• Provides insight into structure of specific pigments, along with associated colors

Chlorophylls

• Describes chlorophyll as a green pigment
• Highlights structural similarities to photosynthetic pigments in plants
• Describes bacteriochlorophyll as the equivalent of chlorophyll in bacteria
• Shows differences in their location within plant cells vs bacterial cells

Carotenoids

• Notes that carotenoids are yellow, red, brown, or green pigments
• Emphasizes the close association with bacteriochlorophyll
• Shows that carotenoids don't play a direct role in photosynthesis
• Describes the transfer of light energy to bacteriochlorophyll and the photoprotective role of carotenoids

Photosynthetic Bacteria

• Provides a branching diagram of photosynthetic bacteria, distinguishing between oxygenic and anoxygenic types
• Details specific examples of photosynthetic bacteria within each branch.

Further Reading

• Lists a book, "Brock Biology of Microorganisms," as a recommended resource for additional study of nutrition, laboratory culture, and metabolism in microorganisms and chapter 5

This quiz assesses your understanding of bacterial physiology and the metabolic diversity of bacteria, as covered in Lecture 6 of the Microbiology course. You'll explore concepts such as energy production, bacterial reproduction, and the classification of bacteria based on their metabolic processes.