Microbial Nutrition Physiology Lecture Notes PDF

# Microbial Nutrition ## First: The Common Nutrient Requirements - **Water:** 70-80% of the cell weight - **Macroelements (Macronutrients):** - Fe, Ca, Mg, K, P, S, N, H, O, C - Required in relatively large quantities - The first six elements (P, S, N, H, O, C) form sugar compounds (ca...

# Microbial Nutrition ## First: The Common Nutrient Requirements - **Water:** 70-80% of the cell weight - **Macroelements (Macronutrients):** - Fe, Ca, Mg, K, P, S, N, H, O, C - Required in relatively large quantities - The first six elements (P, S, N, H, O, C) form sugar compounds (carbohydrates), fats, proteins, and nucleic acids. - Often part of the enzymes - **Trace elements (Microelement elements):** - Zinc, cobalt, molybdenum, nickel, copper, and iodine - Are often part of the enzymes - **Growth factors:** - Very small amounts of substances - They cannot self-synthesize - Including vitamins, amino acids, and some components of nucleic acids - Are involved as cofactors in the action of enzymes ## Second: Nutritional Types of Microorganisms ### A. According to the source of carbon: - **1. Autotrophs:** Use carbon dioxide gas - **2. Heterotrophs:** Use organic compounds ### B. According to the energy source: - **1. Phototrophs:** Light is a source of energy - **2. Chemotrophs:** Oxidize organic or mineral compounds ### C. According to the source of electrons: - **1. Lithotrophs:** Is inorganic molecules - **2. Organotrophs:** Is organic molecules ## Third: Uptake of Nutrients by the Cell - **High molecular-weight complex compounds:** - Such as cellulose, proteins, and fats - Digested by external enzymes secreted by microorganism cells into the external environment through the cell wall. - **Low molecular-weight compounds:** - The entry of these compounds is done in one of the following ways: - **A. Simple diffusion:** - Nutrients enter and exit through the semi-permeable cytoplasmic membrane according to the difference in concentration. - Without using any cellular energy. - **B. Facilitated diffusion:** - The speed of entry and exit of materials increases through the semi-permeable membrane using protein carriers (transport enzymes Permeases) and are located within the plasma membrane. - Without using any cellular energy. - **C. Active transport:** - Nutrients enter by a group of active transport enzymes. - The active transporter which are characterized by their specialization in transport (Specificity). - e.g. Enzyme β-galactosides permease of E. coli bacteria transport sugars. - Other groups in the same bacteria specialize in transporting amino acids. - It is also characterized by its use of cellular energy. ## Fourth: Culture Media - According to the application/chemical composition: - **A. Enriched media:** - **B. Selective media:** - Adding some special chemicals to the nutrient agar medium helps the growth of some microorganisms, while it does not affect others. - Crystal violet is added, it inhibits the growth of some gram-positive bacteria, while it does not affect the growth of some gram-negative bacteria. - **C. Differential media:** - Used to differentiate between different species. - Able to differentiate between the different types of bacteria; the first of which analyzes the added medium and the second of which is unable to analyze it. - **D. Assay media:** - Used to measure the amount of vitamins, amino acids, or antibiotics resulting from the growth of some microorganisms. - **E. Media for Enumeration of Bacteria:** - Used to estimate the numbers of a certain type of bacteria, as is the case with milk or water bacteria. - **F. Media for Characterization of Bacteria:** - Used to isolate bacterial species that have a certain functional ability, as is the case with nitrogen-fixing bacteria or nitrifying bacteria...etc. - **G. Maintenance Media:** - Maintain continued growth. Therefore, some special materials are added to preserve the colony and keep it alive for as long as possible. - There is a gradation in media between solid, semi-solid, and liquid that varies according to the type of bacterial culture. - According to the physical properties: - **1. Solid media:** - The agar is added in the concentration of 1.5-2.0%. - **2. Semi-solid media:** - The agar is 0.2-0.5% agar concentration. - **3. Liquid media:** - Do not contain any traces of solidifying agents, such as agar or gelatin. - According to the type of fermentation: - There are three models of fermentation used in industrial applications: batch, continuous, and fed-batch fermentation. - **1. Batch Fermentation:** - A closed system. - Nothing is added. - **2. Continuous Fermentation:** - An open system. - Sterile nutrient solution is added to the bioreactor continuously, and an equivalent amount of nutrient is simultaneously taken out of the system. - **3. Synchronous Growth:** - During which all bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time. - Can be obtained either: - by manipulating environmental conditions such as by repeatedly changing the temperature - or by adding fresh nutrients to cultures as soon as they enter the stationary phase - or by physical separation of cells by centrifugation or filtration - Diagram of Batch, Fed-Batch, and Continuous Culture - Image of Continuous Culture by Chemostat - Image of Turbidostat - Image of Synchronous Growth The document describes different types of microbial nutrition and then explains how these nutrients are taken up by the cell. The document also describes different types of culture media used to grow microorganisms and how these media are classified. Finally, the document discusses different types of fermentation and how they are used in industrial applications.