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MICROBIAL_NUTRITION_GROWTH_AND_METABOLISM_1666346193754.pptx

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MICROBIAL_NUTRITION_GROWTH_AND_METABOLISM_1666346193754.pptx

  1. 1. MICROBIAL NUTRITION, GROWTH AND METABOLISM
  2. 2. Nutritional requirements • Nutrients are substances used in biosynthesis and energy release • Produce new cellular components and do cellular work • THE COMMON NUTRIENT REQUIREMENTS • Major elements: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus – Components of carbohydrates, lipids, proteins, and nucleic acids – Skeletons or backbones of all the organic molecules – Often satisfied together – Electrons are very important • provide energy for use in cellular work • needed to reduce molecules during biosynthesis • Minor elements: potassium, calcium, magnesium, and iron – Cofactors, heat resistance and stability of ribosomes etc.,
  3. 3. Nutritional requirements • Microelements or trace elements: manganese, zinc, cobalt, molybdenum, nickel, and copper • Supplements : Vitamins, antibiotics • Cannot be synthesized by itself but required for growth – Diatoms need silicic acid (H4SiO4) to construct their beautiful cell walls of silica [(SiO2)n] – Mycoplasma need cholesterol – Growth response assay Balanced mixture of nutrients
  4. 4. NUTRITIONAL TYPES OFMICROORGANISMS • Heterotrophs • Organisms that use reduced, preformed organic molecules as their carbon source • The more reduced the organic carbon source (more electron), the higher its energy content Ex: Lipids > Carbohydrates but not CO2 • Autotrophs • Organisms that use CO2 as their sole or principal source of carbon • Additional energy sources required - light or inorganic or organic molecules • Phototrophs - light as their energy source • Chemotrophs - oxidation of chemical compounds (either organic or inorganic) • Based on the source of electron – Lithotrophs – inorganic substances – Organotrophs - organic compounds
  5. 5. UPTAKE OF NUTRIENTS BY THE CELL • Passive transport • Facilitated Diffusion • Ion channels – Carrier mediated • Active transport – Pumps – Transporters
  6. 6. CULTUREMEDIA • Suitable culture medium is required for growing microorganisms in the laboratory • Solid or liquid preparation used to grow, transport, and store microorganisms • Sources of energy, sources of electron, carbon, nitrogen, phosphorus, sulfur, and various minerals • Definite composition is dependent on the microorganisms – Knowledge of a microorganism’s natural habitat
  7. 7. CULTUREMEDIA • Classification: 1. The chemical constituents from which they are made 2. Their physical nature 3. Their function
  8. 8. CULTUREMEDIA • Agar is a sulfated polymer composed mainly of D-galactose, 3,6- anhydro-L-galactose, and D-glucuronic acid • Why agar? – Melting temp – Hardening properties – Undigested • Koch, Loeffler and Minora Tarazaemon
  9. 9. Growth
  10. 10. Growth curve • Lag Phase: – No immediate increase in cell number occurs – Synthesizing new components – Varies considerably in length • Log Phase: – Maximal rate of growth – Rate of growth is constant • Stationary Phase: – Total number of viable microorganisms remains constant – Balance between cell division and cell death • Death and decline phase: – Nutrient deprivation and the buildup of toxic wastes
  11. 11. Growth curve • Generation time or doubling time
  12. 12. MEASUREMENT OFMICROBIAL GROWTH • Population number or mass • Measurement of Cell Numbers – Direct counting – Easy, inexpensive, and relatively quick; – Gives information about the size and morphology of microorganisms – Petroff-Hausser counting chambers, hemocytometers, Coulter counter and Flow cytometer – Membrane filter technique – Spread plate and pour plate techniques
  13. 13. Coulter counter
  14. 14. MEASUREMENT OFMICROBIAL GROWTH • Measurement of cell mass • Indirect methods • Microbial dry weight – Cells growing in liquid medium are collected by centrifugation, washed, dried in an oven, and weighed – Time-consuming and not very sensitive • Spectrophotometry – More rapid and sensitive – The amount of scattering is directly proportional to the biomass of cells present and indirectly related to cell number
  15. 15. THE CONTINUOUS CULTURE OFMICROORGANISMS • Nutrient supplies are not renewed nor wastes removed – Batch Growth • How to maintain them in long log phase? • Microbial population can be maintained in the exponential growth phase and at a constant biomass concentration for extended periods in a continuous culture system. • Two types Chemostats • Sterile medium is fed into the culture vessel at the same rate as the media containing microorganisms is removed • Limiting nutrient • Growth rate - rate at which new medium is fed • Final cell density - concentration of the limiting nutrient • D = f/V • D – rate of nutrient exchange (dilution rate) • f – medium flow rate • V – vessel volume
  16. 16. THE CONTINUOUS CULTURE OFMICROORGANISMS Turbidostats • Photocell that measures the absorbance or turbidity of the culture in the growth vessel. • Flow rate of media through the vessel is automatically regulated to maintain a predetermined turbidity or cell density • Difference: – Varying D in turbidostat – No limiting nutrients
  17. 17. Water activity and osmotic pressure are inversely related
  18. 18. Oxygen – electron transport chain Pressure – Barotolerant – more than 500 atm Radiations

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