This document discusses microbial nutrition, growth, and metabolism. It covers the common nutrient requirements of microorganisms including major elements, minor elements, micronutrients, and supplements. It also describes the different nutritional types of microorganisms such as heterotrophs and autotrophs. The document then discusses uptake of nutrients by cells, culture media, methods of measuring microbial growth, and continuous culture techniques including chemostats and turbidostats.

1. MICROBIAL NUTRITION,
GROWTH AND METABOLISM

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. 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

5. 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

7. UPTAKE OF NUTRIENTS BY THE CELL
• Passive transport
• Facilitated Diffusion
• Ion channels
– Carrier mediated
• Active transport
– Pumps
– Transporters

10. 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

11. CULTUREMEDIA
• Classification:
1. The chemical constituents from which they are made
2. Their physical nature
3. Their function

12. 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

15. Growth

17. 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

18. Growth curve
• Generation time or doubling time

20. 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

23. Coulter counter

25. 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

26. 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

28. 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

30. Water activity and osmotic pressure are
inversely related

31. Oxygen – electron
transport chain
Pressure – Barotolerant
– more than 500 atm
Radiations