its contents include Introduction, Types of changing, environmental condition, Temperature, Salt concentration, Pressure and Radiation (i.e the harsh conditions in which microbes can survive)

1. TOPIC- Existence and survival of microbes in changing
environmental condition
PRESENTED BY: TAHURA MARIYAM
MSc. MICROBIOLOGY (Sem -II)
P.ID: 19MSCMB009
PRESENTED TO: Dr. Harison Masih (Assistant professor- Sr. Grade)
DEPARTMENT OF INDUSTRIAL MICROBIOLOGY
JACOB INSTITUTE OF BIOTECHNOLOGY AND BIO-ENGINEERING
SAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE,TECHNOLOGY, AND SCIENCES,
PRAYAGRAJ

2. CONTENT
• Introduction
• Types of changing environmental condition
• Temperature
• High temperature
• Optimum temperature
• Low temperature
• Salt concentration
• Halophiles
• Extreme halophiles
• Halotolerant
• Non- halophiles
• Pressure
• Radiation

3. INTRODUCTION
►Microbes are present in diverse habitats, ranging from suitable environment of soil,
water or can be isolated from hostile habitats such as desert, caves, hydrothermal
vents, saline lakes, glaciers etc.
►Term Extremophile is coined for the organisms growing optimally under extreme
environmental conditions of temperature, pressure, salinity and pH but cannot grow
under normal conditions.
►Although extremophiles include different taxa of bacteria and eukarya but archaea
dominate such ecological niches and even some of them survive where conditions
are prohibitive for other life forms.
►Extremophiles are well adapted to unfavorable environmental factors and have huge
biotechnological potential. In order to adapt in harsh conditions of temperature, pH,
alkali etc. microbes modify their cellular and molecular components and sustain
well.

4. Types of changing environmental
condition that affect microbial survival
and existence
• Temperature
• High temperature
• Optimum temperature
• Low temperature
• Salt concentration
• Pressure
• Radiation

5. TEMPERATURE
► Temperature is the most important factor that determines the rate of growth,
multiplication, survival, and death of all living organisms.
► High temperatures damage microbes by denaturing enzymes, transport carriers, and other
proteins.
► Microbial membrane are disrupted by temperature extremes.
► At very low temperatures membranes also solidify and enzymes also do not function
properly.

6. CLASSIFICATION OF BACTERIA ACCORDING
TO GROWTH TEMPERATURE

7. 1) PSYCHROPHILES/CRYOPHILES-
►The term psychrophile was first used by Schmidt-
Nelson.
►Extremophilic organisms that are capable of
growth and reproduction in cold temperatures
►Temperature range: −20°C to +10°C.
►Examples: Oscillatoria, Chlamydomonas nivalis,
Methanogenium, etc.

8. 2) MESOPHILES-
1. Grows best in moderate
temperature.
2. Temperature range: 20°C to
45°C.
3. Examples: Escherichia coli,
Streptococcus pneumoniae, etc.

9. 3) PSYCHROTROPHS-
1. Cold‐tolerant bacteria.
2. Have optimal and maximal growth temperatures
above 15 and 20°C, respectively.
3. Psychrotrophic bacteria and fungi are the principal
cause of spoilage of refrigerated food.
4. Examples: Pseudomonas, Aeromonas, Bacillus,
Clostridium, etc.

10. 4) THERMOPHILES-
1. Derived from Greek word thermotita meaning heat and philia meaning love.
2. Heat-loving microorganisms.
3. Grow at 50°C or higher. Their growth minimum is usually around 45°C and often
optima between 50 and 80°C.
4. Examples: Thermus aquaticus, Geogemma barossii, etc.

11. 5) HYPERTHERMOPHILES-
1. Thrives in extremely hot environments.
2. Temperature range: 80°C to 113°C.
3. First discovered by Thomas D. Brock in 1965 , in hot springs in Yellowstone
National Park, Wyoming.
4. The cell membrane contains high levels of saturated fatty acids to retain its shape
at high temperatures
5. Examples: Sulfolobus, Methanococcus jannaschii, Thermotoga, etc.

12. 1. CELL MEMBRANE MODIFICATIONS
• Molecular mechanisms used by two distinct groups of hyperthermophiles archae
and bacteria to survive under high temperatures, differ markedly.
• Membrane lipids of archae differ from that of bacterial cells by the presence of an L-
isomer of glycerin, instead of Dglycerin.
• Such modifications of membrane lipids, as acylation, saturation, branching and (or)
formation of cyclic structures of hydrocarbon chains have been found in bacteria,
growing under high temperatures

13. 2. DNA AND RNA MODIFICATIONS
• Denaturation resistance of DNA under extreme conditions of archaebacteria habitation is
attributed by positively charged DNA binding proteins.
• Several structural variations of cellular polyamines, stabilizing DNA, as well as secondary
structures of RNA in extremophilic archaebacteria exist.
• The higher content of G–C pairs can be also the reason for additional stabilization of DNA
structure in hyperthermophiles, as it is more stable due to an additional hydrogen bond in
comparison with the adenine-thymine (A–T) pair.
• The increase of stability of secondary and tertiary structures of tRNA is also attained by
posttranslational nucleoside modification; a number of such modifications are hallmark of
archaebacteria

14. HEAT SHOCK RESPONSE
• The heat shock represents a ubiquitous protective and homeostatic cellular response
to cope with heat-induced damage in proteins.
Types of Heat Shock Responses
• here are two types of heat shock responses.
• 1. Heat shock response against cytoplasmic thermal stress
• 2. Heat shock response against periplasmic thermal stress

15. SALT CONCENTRATION
• On the basis of salt concentration there are 2 types of microorganisms:
a) Halophiles: organisms that grow best at reduced water potential; have a specific
requirement for NaCl.
b) Extreme halophiles: organisms that require high levels (15-30%) of NaCl for
growth.
c) Halotolerant: organisms that can tolerate some reduction in water activity of
environment but generally grow best in the absence of the added solute.
d) Non- halophiles: Microbes that require a high water activity (near or at 1) are
termed nonhalophiles. Non-halophiles grow best in media containing less than 0.2
M salts while halophiles grow best in media containing from 0.2 to 5.2 M
dissolved salts.

16. HALOPHILES
• Halophilic extremophiles, or simply
halophiles, are a group of microorganisms
that can grow and often thrive in areas of
high salt (NaCl) concentration.
• These hypersaline areas can range from the
salinity equivalent to that of the ocean (~3-
5%), up to ten times that, such as in the
Dead Sea (31.5% average).
• Halophiles have been found belonging to
each domain of life but primarily consist of
archaea. They are metabolically diverse,
ranging from simple fermenters to iron
reducers and sulfide oxidizers.
Halophilic Archaea

17. Halophile classification
Slight Halophile Moderate Halophile Extreme Halophile
Percent Salt 2 - 5% 5 - 20% 20 - 30%
Molarity 0.34 - 0.85 M 0.85 - 3.4 M 3.4 - 5.1 M

19. PRESSURE
• The vast majority of microbes, living on land or water surface, are exposed to a
pressure of approximately 1 atmosphere. But there are microbes that live on the
bottom of the ocean, where the hydrostatic pressure can reach 600-1,000 atm. These
microbes are the barophiles(“pressure lovers”), microbes that have adapted to
prefer and even require the high pressures. These microbes have increased
unsaturated fatty acids in their plasma membrane, as well as shortened fatty acid
tails.

20. 1- PIEZOPHILES
• Piezophiles are microorganisms that have adapted to high-pressure environments and
can grow more easily under high hydrostatic pressure conditions than at atmospheric
pressure.
• Piezophiles are widespread in the seafloor and deep within the Earth’s crust.

21. 2) BAROPHILES
• Barophile is a bacterium which prefers to grow or exclusively grows at moderately
high hydrostatic pressures such as the challenger deep in the marianas trench
which has a depth of 10,994 m.
• Barophilic bacteria are best adaptedwith growth pressure greater than 40mpa
whereas moderately barophilic bacteria grow ideally above 1 atm but less than
40mpa.

22. RADIATION
• Ionizing radiation, such as x-rays and gamma rays, causes mutations and destruction of the cell’s
DNA.
• While bacterial endospores are extremely resistant to the harmful effects of ionizing radiation,
vegetative cells were thought to be quite susceptible to its impact.
• Ultraviolet (UV) radiation also causes damage to DNA, by attaching thymine bases that are next to
one another on the DNA strand.
• These thymine dimers inhibit DNA replication and transcription. Microbes typically have DNA
repair mechanisms that allow them to repair limited damage, such as the enzyme photolyase that
splits apart thymine dimers.

23. REFERENCE
• Resistance of Microorganisms to Extreme Environmental Conditions and Its
Contribution t Astrobiology
• Microbiology, P.D. Sharma
• www.slideshare.net
• General Microbiology, C.P Powar