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Microbial growth and Growth control - (iv Effect of Temperature on…
Microbial growth and Growth control - (iv Effect of Temperature on Microbial Growth)
Microbial Life at Hot Temperature
around 65 degree celcius (only prokaryotic life form exist)
Thermophiles; growth temperature optima between 45-80C
Hyperthermophiles; growth with optima greater than 80C and inhabit hot environment including boiling hot spring, seafloor hydrothermal vents
Chemoorganotrophic and chemolithotrophic are present
High prokaryotic diversity (Archaea and Bacteria present)
Taq polymerase; automate repetitive steps in the PCR technique
Studies thermal habitat revealed that:
1) Prokaryotes are able to grow at highest temperature than eukaryotes
2) Non-phototrophic organisms can grow at higher temperature than phototrophic organisms
3) Organism that have highest temperature optima is Archaea
Adaptations
1) Enzyme and protein function optimally at high temperatures
Critical amino acid substitution in a few location provide more heat tolerant fold
An increased number of ionic bond between basic and acidic amino acid resist unfolding in the aqueous cytoplasm
Production of solute to stabilize protein; diglycerol phosphate, inositol phosphate
2) Modification in cytoplasmic membrane to ensure heat stability
Bacteria have lipid rich in saturated fatty acid
Archaea have lipid monolayer rather than bilayer
Microbial Life in the Cold
Extremophiles; Organisms that grow under very hot and very cold condition
Psychrophiles; Inhabit permanently cold temperature
Psychrotolerant; Organisms that can grow at 0c but have optima at 20-40c and most widely distributed than Psychrophiles
Adaptations of psychrophily
1) Production of enzyme that function optimally in the cold
More alpha helices than beta sheets
Fewer weak bond
More polar and less hydrophobic amino acid
Decreased interaction between protein domains
2) Transport process function optimally at low temperature
Modified cytoplasmic membrane as it has high unsaturated fatty acid content
Temperature Classes of Microorganism
Temperature is a major environmental factor controlling microbial growth
Cardinal temperature- the minimum,optimum,maximum temperature at which an organism grows
Minimum- Membrane gelling; transport process so slow that growth cannot occur
Maximum- protein denaturation; collapse of cytoplasmic membrane; thermal lysis
Optimum- enzymatic reaction occuring at maximal possible rate
Microorgasims can be classified into group by their growth temperature optima
Mesophile (Midrange temperature);
Eschecheria coli
Thermophile (High temperature);
Alicyclobacillus
Psychrophile (low temperature);
Polaromonas vacuolata
Hyperthermophile (Very high temperature);
Thermococcus celer
