Summary
Summary MCB2022S Final Module Complete notes
- Institution
- University Of Cape Town (UCT)
This set of notes contains work on: - microbial nutrients - microbial growth - vitamins - antibiotics - bioremediation - biomining
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Microbial NutrientsGrowth requirements
- Carbon source
- Cellular energy source
- Source of reducing power
o High energy e-/H
o NADH/NADPH
Nutrients
- Required from environment and used for cellular acCviCes
- EssenCal nutrients = any substance (elemental or molecular form) that must be
provided to organism
- Macronutrients = required in large quanCCes and play principal role in cell structure
and metabolism
o CHNOPS
- Micronutrients = trace elements present in smaller amounts + involved in enzyme
funcConing and protein structure maintenance
o Mn, Zn, Ni
Inorganic vs Organic
- Inorganic = atom or simple molecule with a. combinaCon of atoms other than C and
H
- Organic = C and H
o Product of living things
Nutrient AbsorpCon
- Necessary nutrients must be taken up and waste products must be expelled
- Transport occurs across cell membrane
o Specialized transport structure
o Cell wall is too nonselecCve to screen entrance and exit molecules
NutriConal Types
- Heterotrophs = organic carbon source
- Autotrophs = CO2 carbon source
- Phototrophs = light energy
- Chemotrophs = chemical energy
Chemical Requirements
1) Carbon
a) Structural backbone of organic molecules
b) Used as an energy source + make other macromolecules
c) Heterotrophs use organic C source
i) Dependent on other life forms
d) Autotrophs use CO2
i) Self feeders
ii) Have the capacity to convert CO2 into other carbon compounds
,2) Hydrogen
a) Used for making macromolecules
b) Acquired via organic and inorganic compounds like H2O, salts and certain natural
gases
c) Helps to maintain pH + formaCon of hydrogen bonds
d) Source of free energy in respiraCon
3) Nitrogen
a) Structure of proteins and nucleic acids
b) Must reduce N2 to ammonium (NH4+) before incorporaCon
c) FixaCon of N2 from atmosphere can be done by few bacteria
4) Sulfur
a) Used in some amino acids and vitamins
i) Methionine
ii) Cysteine
b) Can decompose protein for sulfur source
5) Phosphorous
a) Used in nucleic acids and cell membranes
b) EssenCal to geneCcs
c) Phosphate ion = major source of phosphorous in rocks
6) Trace elements
a) Inorganic elements required in small amounts
b) Used in enzyme cofactors
c) Iron, copper, zinc
7) Oxygen
a) Obtained from organic compounds and inorganic salts like sulfates, phosphates,
nitrogen and water
b) Important role in structural and enzymaCc funcCons of the cell
,Oxygen processing
- Can be transformed into toxic products
o Single oxygen (O) = reacCve molecule that can cause oxidaCon of membrane
lipids
o Superoxide ion (O2-) = toxic hydrogen peroxide, toxic to cells and used as a
disinfectant
o Hydroxyl radicals = reacCve
§ Can steal e- from neighbouring atoms
- Microbes use enzymes to scavenge and neutralize reacCve oxygen by-products
o Toxic O2 products can be converted to a harmless substance if:
§ Catalase
• Breaks down H2O2 to H2O and O2
• EssenCal to live in O2 rich environment
§ Peroxidase
• Not essenCal
• Can detoxify H2O2 to H2O
o For microbes that can growth with or without O2
(aerotolerant will not have catalase)
§ Superoxide dismutase (SOD)
• Converts O2- to H2O2 and O2
• EssenCal to live in O2 rich environment
o Two step process à
§ Superoxide ion to H2O2 and O2 using SOD
• NB for aerobic and facultaCve anaerobic microbes in the
presence of O2
§ H2O2 to H2O and O2 by catalase (neutralizaCon reacCon)
• Occurs for microbes that use O2
§ If microbe can grow with or without O2 à wont have catalase but will
have peroxidase (aerotolerants)
, Microbial Growth
How Microbes Grow
1. Binary fission
o Parental cells enlarge and chromosomes are duplicated
o Cell envelope invaginates and pinches in the centre to form septum
o Forms two idenAcal daughter cells
o FtsZ proteins à assemble to form a Z ring that is anchored to the plasma membrane
§ Z ring pinches cell envelope to separate the cytoplasm into 2 new cells
- GeneraAon Time
o Doubling Ame
o Time required for a complete fission cycle (each fission cycle doubles the populaAon
size)
§ Will be at a constant rate in favourable environmental condiAons
o Measure of the growth rate of an organism
- Growth Curves
1. Lag phase
Cells are synthesising new components to:
1. Replenish spent materials
2. Adapt to new medium/other conditions • Length of lag phase varies
How to shorten lag phase —> Take cells from log phase and introduce to identical medium
at same temp (no adjustment to medium needs to take place)
2. Exponential phase
• Aka log phase
• Rate of growth and division is constant and maximal
• Cell population is most uniform in terms of chemical/physical properties
• Cells display balanced growth (=cellular constituents are manufactured at
constant rates relative to each other)
• Unbalanced growth = rates of synthesis of cell components vary relative to each
other • Caused by:
• Change in nutrient levels
• Shift up —> poor medium to rich medium
• Shift down —> rich medium to poor medium
• Change in environmental conditions
• Temperature
• pH
• [salt]
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