Question

Classify the bacteria on their physical condition

Answer 1

1. Psychrophiles:

Bacteria that can grow at 0°C or below but the optimum temperature of growth is 15 °C or below and maximum temperature is 20°C are called psychrophiles

Psychrophiles have polyunsaturated fattyacids in their cell membrane which gives fluid nature to the cell membrane even at lower temperature.

Examples: Vibrio psychroerythrus, vibrio marinus, Polaromonas vaculata, Psychroflexus

2. Psychrotrops (facultative psychrophiles):

Those bacteria that can grow even at 0°C but optimum temperature for growth is (20-30)°C

3. Mesophiles:

Those bacteria that can grow best between (25-40)C but optimum temperature for growth is 37C

Most of the human pathogens are mesophilic in nature

Examples: coli, Salmonella, Klebsiella, Staphulococci

4. Thermophiles:

Those bacteria that can best grow above 45C.

Thermophiles capable of growing in mesophilic range are called facultative thermophiles.

True thermophiles are called as Stenothermophiles, they are obligate thermophiles,

Thermophils contains saturated fattyacids in their cell membrane so their cell membrane does not become too fluid even at higher temperature.

Examples: Streptococcus thermophiles, Bacillus stearothermophilus, Thermus aquaticus,

5. Hypethermophiles:

Those bacteria that have optimum temperature of growth above 80C.

Mostly Archeobacteria are hyperthermophiles.

Monolayer cell membrane of Archeobacteria is more resistant to heat and they adopt to grow in higher remperature.

Examples: Thermodesulfobacterium, Aquifex, Pyrolobus fumari, Thermotoga

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