Extremophiles are microorganisms that thrive in extreme environments. Psychrophiles, or cold-loving microorganisms, can grow and multiply at temperatures as low as 0°C. They are found in cold environments like polar regions and deep oceans. Psychrophiles have adapted mechanisms to function at low temperatures, including cold shock proteins that regulate genes involved in stress response. They play important roles in nutrient cycling. Examples of psychrophilic bacteria include Pseudomonas and Bacillus. Radiodurant microbes like Deinococcus radiodurans are resistant to ionizing radiation, desiccation, and acid. They can repair double-strand DNA breaks through homologous recombination within 24 hours, allowing

1. EXTREMOPHILES
Ankita Behera
M.Sc Microbiology
St. George College of Management & Science
Bengaluru North University

2.  Micro-organisms in extreme environment is known as EXTREMOPHILES.
 Extremophile are those whose optimal growth conditions land outside the normal environment conditions.
 Many part of our earth contain extreme environment such as high temperature zones like volcanic zones
,polar regions, acidic and alkalophilic springs and cold pressurized depths of oceans.
 Many micro-organisms are found adapted to exceptional environments.
 Extremophiles are the micro-organisms that not only survive but successfully grow and flourish in
environment where normal life cannot.
 The important groups of micro-organisms in extreme environments are reffered as –
1)ACIDOPHILES
2)ALKALOPHILES
3)HALOPHILES
4)THERMOPHILES AND HYPERTHERMOPHILES
5)PSYCHROPHILES
6)BAROPHILES
7)OSMOPHILES
8)RADIODURANT MICROBES.

3. PSYCROPHILES

4. Temperatures in many parts reach above 5 degree
celcius because 70% of the earth is covered by deep
oceans providing cold conditions.
J.FOSTER in 1887 was first to see the growth and
reproduction of bacteria at low temperatures.
The term psychrophilic was used in 1902 by
S.SCHMIDT-NIELSON to describe micro-organisms
can grow and multiply at 0 degree celcius.
Also known as cold loving
Can also named as “pschrotrophic” and cold-blooded
animals.

5. Pschrophiles contribute to the
1]nutrient cycling.
2]biomass production
3]metabolic activities like
photosynthesis,nitrogen
fixation,methanogenesis and
degradation of natural and
xenobiotic organic compounds.

6. MICRO-ORGANISMS FOUND IN THOSE
TEMPERATURES:-
• BACTERIA:-Pseudomonas , Bacillus , Alcoligenes ,
Arthrobacter glacilis , Micrococcus criophilus , Vibrio
psychroerythrus , Aquaspirillum articum , Shiwanella
frigidimarina
• Microalgae:-Chlamydomonas nivalis
• Yeasts:- Candida , Cryptococcus , Rhodotorula ,
Sacchromyces.
• Fungi:-Penicillium , cladosporium

8. PSYCHROPHILLIC ORGANISMS UNDER
SCANNING ELECTRON MICROCOPE

9. ADAPTIVE MECHANISMS TO COLD
Cold adapted micro-organisms have evolved a complex
range of adaptions of their cellular constituents including
membranes,
Protein synthesis,
enzymes,
Energy-generating system
And
The components responsible for nutrient uptake to survive and
grow successfully in cold habitats.

10. When temperature decreases water begins to freeze leaving a more
conc.salts solution outside the microbial cells.
In response to that the micro-organisms will accumulate intracellular
compatible solutes to counteract the imposed osmotic stress and to
maintain cellular enzyme function.
but
A point will be reached when enzymes fail and intracellular ice may
begin to form.
So,the phenomenon of cold denaturation of proteins is well documented
as it generally occurs at temperature below -15 degree celcius. cold
denaturantion of protein due to sudden decreases in temperature
performs alteration in gene expression known as the “cold-
shockresponse”

11. • This response is distinct from general stress response
known as “cold shock” response which involves the
induction and synthesis os “cold shock proteins”.
• The cold shock proteins are “CspA” whose functions
are protein synthesis and mRNA folding and
sometimes act in freeze protection.
• CspA protein regulate gene expression involved in
DNA supercoiling and also RNA chaperones

12. BIOTECHNOLOGICAL APPLICATIONS
• In food biotechmology it is used for food preservation
taste improvement in alcoholic bevarages, frozen
foods , meat tenderising.
• Fine chemicals like organic phase biocatalysis.
• Low-energy waste treatment.
• Bioremediation process.etc

13. RADIODURANT MICROBES

14. RADIODURANS is an extremophilic
bacteria which are resistant to
radioactive.
It can survive in cold,dehydration,
vaccum and acid which makes them
known as “POLYEXTREMOPHILE”.
EX:-Deinococcus radiodurans

17. It is a rather large , spherical bacterium , with a
diameter of 1.5-3.5 um.
4 cells normally stick together forming a tetrad.
They are easily cultured and do not appear to cause
disease.
Colonies are smooth , convex and pink to red is color.
Cell stain gram positive although its cell envelope is
unusual.
They donot form endospore and is non-motile.

18. • It is an obligate aerobic chemoorganoheterotrophs .
• It is often found in rich in organic materials and can be
isolated from dried foods ,room dust , medical
instruments and textiles.
• It is extremely resistant to ionizing radiation, uv light ,
oxidizing and electrophilic agents.
• Its genome consists of 2 circular chromosomes and
3195 genes.

19. IONIZING RADIATION RESISTANCE
MECHANISMS:-
• Deinococcus radiodurans accomplishes its resistance to radiation by
having multiple copies of genome and DNA repair mechanisms.
• It usually repairs the break in its chromosomes within 12-24 hrs through
2 step process:-
1}firstly, they reconnect some chromosome fragments through a process
called single-stranded annealing.
2}secondly, a protein mends double-strand breaks through homologous
recombination.
This process doesnot introduce any more mutations than a normal
round of replication would.

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