Psychrophiles and psychrotrophs are types of extremophiles that can grow in cold temperatures. Psychrophiles can grow between -20°C to 10°C and have an optimal growth temperature of 15°C or lower, while psychrotrophs have a minimum growth temperature of around 4°C and can grow up to 44°C. Both are found in permanently cold environments like polar regions and deep sea. They have been isolated from various food products as well and play a role in biodegradation of organic matter during cold seasons.

1. PSYCHROPHILES AND
PSYCHROTROPHS
BY- MOHIT HINSU

2. EXTREMOPHILE?
■ a microorganism, especially an archaean, that lives in conditions of extreme
temperature, acidity, alkalinity, or chemical concentration.
■ An extremophile is an organism that thrives in extreme environments.
Extremophiles are organisms that live in "extreme environments," under high
pressure and temperature
■ Three examples of extremophiles are Picrophilus torridus (a thermoacidophile
adapted to hot, acidic conditions), Antarctic krill (a psychrophile), and the
Pompeii worm (a thermophile).
■ Classes of extremophiles include acidophiles (acid lovers), halophiles (salt
lovers), psychrophiles (extreme cold lovers), and radiophiles (radiation lovers).
Tardigrades or water bears can survive varied extreme conditions including
excess dryness, lack of oxygen, extreme cold, low pressure, and toxins.

3. IMPORTANTTERMS
■ The Thermal death point [TDP]is the lowest temperature that is required to kill
a population of microbes when applied for a specific time.
■ Thermal death time:It is the specific time [shortest time] that is required for
killing the standard suspension of microorganism at a definite temperature.
■ D-value or decimal reduction time is the time required, at a given condition
(e.g. temperature) or set of conditions, that is, to kill 90% of relevant
microorganisms.

4. ■ Each and every microorganism has a cardinal range of temperature for its growth
and they are minimum temperature, optimum temperature, and maximum
temperature.
■ 1.Minimum temperature :The temperature below which growth of microbes does
not take place is called minimum growth temperature.
■ 2. Optimum temperature:The temperature at which there is an maximum growth of
microbes is called as optimum growth temperature.
■ 3. Maximum temperature :The temperature above which the growth of microbes
doesn’t take place is called maximum growth temperature.

5. PSYCHROPHILES:
■ Psychrophiles or cryophiles (adj. psychrophilic or cryophilic) are extremophilic organisms
that are capable of growth and reproduction in low temperatures, ranging from −20 °C to
+10 °C.They are found in places that are permanently cold, such as the polar regions and
the deep sea.
■ Example: Psychrobacter pasteurii , Arthrobacter citreus , Psychrobacter salsus
■ Cold loving.
■ Minimal growth temperature: 0 Celsius or lower
■ Optimal growth temperature :15 Celsius or lower
■ Maximal growth temperature :20 Celsius
■ Higher than the 20 Celsius psychrophiles not found.

6. PSYCHROTROPHS:
■ Psychrotrophs are cold-tolerant bacteria or archaea that have the ability to grow at low
temperatures.
■ Cold tolerant.
■ Minimal growth temperature: About near 4 Celsius
■ Optomal growth temperature : 20-40Celsius
■ Maximal growth temperature : Around 44 Celsius
■ Higher than the 20 Celsius psychrotrophs easily grow well.

8. ■ Psychrophiles and psychrotrophs microorganisms are not only confined to the
polar region but have been isolated from diverse range of temperature
environment.
■ They have been isolated from dairy products including raw and pasteurized milk
, cream and butter ,chilled sored beef and vegetables.
■ These data indicates that both microorganisms are ubiquitious in nature and are
present in a diverse range of habitats.
■ The characteristics features of pshychrophiles and pshycrotrophs that they are
predominantly gram negative , aerobic , asporogenous , rod shaped bacteria.
■ However in natural microbial ecosystems pshychrophiles and pshycrotrophs
microorganism can play a large role in the biodegradation of organic matter
during cold seasons.