Microbiology_4_growth

Microbial Growth and Evolution

• The presentation covers different aspects of microbial growth and evolution, suitable for an MPharm program.
• Learning objectives include microbial culturing methods, bacterial and viral growth stages, and bacterial evolution.

Top 10 Elements in Bacteria

• Key elements making up a bacterium are listed along with their percentage of dry weight.
• The sources and functions of each element are outlined with explanations.
• Elements like carbon, oxygen, nitrogen, hydrogen, phosphorus, and sulfur make up the largest portion of dry weight, vital for cellular structures and processes.

Sources of Carbon, Energy & Electrons

• Autotrophs obtain carbon from CO2, whereas heterotrophs obtain it from other organisms.
• Phototrophs utilize light, and chemotrophs use compound oxidation for energy.
• Lithotrophs use reduced inorganic compounds, and organotrophs use organic molecules as electron sources.
• These terms can be combined (e.g., chemoorganoautotroph).

In-vitro Microorganism Culture

• In-vitro techniques involve culturing microorganisms in liquid or solid media.
• Liquid media produces a suspension of cells, while solid media allows colony development, aiding purification and differentiation.
• Originally utilizing potato slices and gelatin, the process has evolved to use agar for solid media. Key factors include media composition and the gelling agent—agar.

Undefined vs Defined Media

• Undefined media utilizes undefined components, mostly organic extracts from yeast, vegetables, and meats. This leads to batch-to-batch variation.
• Defined media uses chemically defined components, high reproducibility, and allows for rich or minimal nutrient content in the media.
• Both media have varying formulas, but the composition and reproducibility differ significantly. Specific examples of undefined and defined media are provided for comparison.

Atmospheric Requirements

• Obligate aerobes need oxygen to survive and function.
• Obligate anaerobes cannot tolerate oxygen and are susceptible to it.
• Facultative anaerobes can thrive with or without oxygen.
• Microaerophiles require low oxygen concentrations.
• Aerotolerant anaerobes can tolerate oxygen but don't use it for metabolism.

Anaerobic Microorganisms

• Various methods exist for cultivating anaerobic microorganisms, with specialized cabinets and gas-generating sachets like GasPak as common.
• Anaerobic culture methods primarily focus on reducing oxygen levels (or eliminating it) for successful culturing without harmful oxygen impact.
• Candle extinction and GasPak are methods used to create anaerobic environments.

Bacterial Cell Division

• Most bacteria reproduce asexually through binary fission.
• Some reproduce through budding.
• Generation time varies significantly between bacterial species; examples are given to contrast the variation in time for cell reproduction.
• The presentation highlights the four distinct phases of bacterial growth.

Bacterial Growth

• Lag phase is characterized by no immediate increase in cell number.
• Exponential (log) phase is marked by maximum growth and regular doubling time.
• Stationary phase occurs when nutrients are depleted, causing a cessation of growth.
• Death phase involves declining cell numbers due to toxic waste and nutrient scarcity.

Microbial Metabolism

• Microbial metabolism is categorized into primary and secondary metabolism.
• Primary metabolism involves essential pathways for energy production and cell component synthesis.
• Secondary metabolism utilizes non-essential pathways to produce natural products (e.g., antibiotics) and metabolic products potentially crucial in pathogenicity.

Laboratory Scale Culture

• Flask cultures are closed systems utilized for optimization and step-wise testing in a closed environment.
• Chemostats are open systems that allow for highly controlled growth using a constant nutrient supply Both techniques have distinct applications (and limitations) but allow for laboratory-scale culture control & reproducibility.

Scaling Up Production

• Scaling cultivation techniques from laboratory flasks to larger-scale bioreactors involves specific steps and considerations. Several techniques are used for scaling up production for industrial use, involving precise and systematic methods needed for maximizing output from a specific process.

Bulk Culturing

• Different culturing modes like batch, fed-batch, and continuous are crucial for optimizing large-scale culturing.
• Critical parameters (mixing, oxygen levels, pH, temperature, foam control, and initial concentration) are important for controlling bulk culturing.

Viral Replication

• Viral replication involves subverting the host's replication machinery.
• Bacteriophages cause lytic replication and cell destruction.
• Eukaryotic viruses often bud out of the cell without killing it; examples include influenza and HIV.
• The mechanisms (lytic, lysogenic) and the host-virus interaction are highlighted.

Bacterial Evolution: Mutation

• Mutations are permanent changes in a single cell’s DNA that are not always immediately detectable or transferable to daughter cells
• Different types of mutation exist (e.g., beneficial, deleterious, neutral), each having specific impacts on the organism.
• Environmental factors like radiation can increase mutation frequency.

Bacterial Evolution: DNA Acquisition

• Bacteria can evolve through transformation, transduction, and conjugation—mechanisms for acquiring genetic material.

Why Should I Care?

• Understanding microbial evolution is crucial for various applications.
• Evolution directly relates to antimicrobial resistance.

Bacterial Evolution: Antimicrobial Resistance

• Antibiotic usage can drive bacterial evolution through selective pressure—favoring resistant strains and decreasing susceptible strains
• Antibiotic resistance often involves a combination of mechanisms rather than a single mutation, emphasizing the complexity of this process.

Strain Improvement

• Improving bacterial strains is vital for boosting product yield.
• Natural methods exist (e.g., spontaneous mutation).
• Several techniques (mutagen exposure and genetic modification) can enhance efficiency.
• Specific examples (historical use of mutagenesis in Penicillium chrysogenum) illustrate strain improvement strategies.

Heterologous Gene Expression

• Heterologous gene expression (e.g., insulin production in E. coli) allows the production of desired proteins from different organisms in a controlled environment.

Summary

• The presentation summarizes the key concepts of microbial growth, evolution, different culturing techniques, and their importance in the pharmaceutical sector.
• The presentation covers the evolution processes and importance of resistance to antibiotics, as well as strain improvement methods.

Extra Reading

• Further reading materials, such as Prescott's Microbiology and Brock Microbiology, are suggested for more detailed study.

Test your knowledge of bacterial growth phases, anaerobic culture methods, and the nutritional requirements of bacteria. This quiz covers essential concepts related to how bacteria grow and metabolize in various environments. Challenge yourself with questions about bacterial characteristics and energy sources.