This document summarizes different ways to classify microorganisms based on their oxygen requirements, carbon sources, temperature preferences, pH tolerance, and pressure tolerance. It discusses obligate aerobes and anaerobes, facultative anaerobes, microaerophiles, and aerotolerant anaerobes based on their oxygen needs. It also describes photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs based on their carbon sources. Microbes are further classified as psychrophiles, mesophiles, thermophiles, hyperthermophiles, acidophiles, neutrophiles, and alkalophiles based on their temperature and

2. CONTENTS
 MICROORGANISMS BASED ON O2 REQUIREMENTS
 MICROORGANISMS BASED ON CARBON
SOURCES(Nutritional Forms)
 MICROORGANISMS BASED ON TEMPERATURE
REQUIREMENTS
 MICROORGANISMS BASED ON pH
 MICROBES ADJUSTMENT TO DIFFERENT PRESSURE.
 REFERENCES
2

3. Growth of Microbes
 Increase in number of cells,
not cell size
 One cell becomes colony of
millions of cells

4. Factors Regulating Growth
 Oxygen,Sulphur,Nitrogen,Iron
Etcetera
 Nutrients E.g Carbon Sources
 Environmental conditions:
temperature, pH, osmotic pressure
 Generation time

5.  MICROORGANISMS BASED ON O2
REQUIREMENTS
 Obligate aerobe
i) Grow only when
oxygen is present
(Mycobacterium
tuberculosis will grow
only in present of free
oxygen)
ii) completely
dependent on
atmospheric oxygen
for growth
5
Mycobacterium tuberculosis

6. MICROORGANISMS BASED ON O2 REQUIREMENTS
 Obligate (strict)
anaerobes
 i) Die in present of
oxygen i.e. do not
tolerate oxygen
 e.g. Clostridium,
Fusobacterium
nucleatum will grow
only in absence of
oxygen which is toxic
to them.
Fusobacterium nucleatum
Why they are sensitive to O2?

7. MICROORGANISMS BASED ON O2 REQUIREMENT
 Facultative anaerobes
 i) Grow with or without
oxygen, grow better in
oxygen (respire)
 ii) Do not require oxygen for
growth, but do grow better in
its presence
(Saccharomyces (yeast)
will grow in the absence of
oxygen, but more slowly
than if oxygen were
present)
7
Escherichia coli

8. MICROORGANISMS BASED ON O2 REQUIREMENT
 Microaerophiles
 i) Damaged by the
normal atmospheric
level of oxygen
 ii) But require lower
levels (2 – 10%) for
growth.
8 Helicobacter pylori

9. MICROORGANISMS BASED ON O2 REQUIREMENT
 Aerotolerant
anaerobes
 i) Ignore oxygen
 ii) Grow equally well
with or without oxygen.
 E.g Lactobacillus
acidophilus occurs
naturally in the
human and animal
gastrointestinal tract
and mouth.
9
Lactobacillus acidophillus

10. 10

11.  MICROORGANSIMS BASED ON CARBON
SOURCES(Nutritional Forms)
Carbon source
 Photoautotroph:E.g Photosynthetic
Bacteria(Thiospirillum, Chlorobacterium).
 Chemoautotroph:E.g Sulphur
Bacteria(Thiobacillus,Thiothrix).Iron
Bacteria(Ferrobacillus).
 Photoheterotroph:E.g Purple Non-Sulphur
Bacteria.
 Chemoheterotroph:E.g Protozoa

12. Organisms Carbon
source
Energy source
Photoautotrophs CO2 sunlight
Chemoautotrophs CO2 Simple inorganic
chemicals
Photoheterotrophs organic sunlight
Chemoheterotrophs organic Metabolizing organic
compounds
12

13.  MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
CARDINAL TEMPERATURE:
Organisms exhibit distinct Cardinal Temperatures
 Minimum – below which no growth occurs
 Optimum – at which fastest growth occurs
 Maximum – above which no growth occurs
13

14. 14
 MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
Microbes adapted to different temperature ranges
Stenothermal organisms:
Have a narrow range of cardinal growth temperatures
Eurythermal organisms:
Have a wide range of cardinal growth temperatures

15. 15
 Low temperature
 Enzymatic reactions too slow; enzymes too stiff
 Lipid membranes no longer fluid
 High temperature
 Enzymes denature, lose shape & stop functioning
 Lipid membranes get too fluid, leak
 DNA denatures
 As temperature increases, reactions and growth rate speed
up;at max, critical enzymes denature.
MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
Why does growth affected by
LOW and HIGH Temperature?

16. 16
 MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
 Psychrophiles/Cryophiles (Cold loving)
 Can grow well at 0ºC
 Have optimal growth at 15ºC or lower & usually will not grow
above 20ºC. (e.g. Bacteria that cause food to spoil in the
fridge).These bacteria generally live in cold water & soil
 none can survive in the human body.
(e.g. Vibrio marinus grow in food and dairy products when
refrigerated)

17. 17
 MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
Psychrotroph (facultative psychrophiles):
 Can also grow at 0ºC, but have growth optima between
20 & 30ºC, & growth maxima at about 35ºC.
 Mesophile:
 Growth minima of 15 – 20ºC
 Growth optima between 20 – 45ºC
 Maxima of about 45ºC or lower
 Human pathogens are included in this group. E.g
Corynbacterium dephtherius, Nesseria gonorrhoea (30
-37ºC)

18. 18
 MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
 Thermophile (Heat loving)
 Growth minima around 45ºC
 Optima of 55 – 65ºC.
 Enzymes are heat stable, also ribosome work at higher
temperature.
 Temperature effect is generally on enzyme stability i.e.
high temperatures tend to denature proteins. However,
thermophiles are becoming attractive to industry because
chemical reactions tend to be more efficient at higher
temperatures
E.gThurmus aquaticus (45-70ºC) –not pathogenic to human

19.  MICROORGANISM BASED ON
TEMPERATURE REQUIREMENTS
Hyperthermophiles (mostly Archaea
in this group):
 Growth minima around 55ºC
 Optima of 80 – 110º
 Some can survive temperatures as high as 110ºC in
boiling hot springs or in deep sea –vents
19

20. 20
How can microbes(ARCHAEA)Can Survived
EXTREME TEMPERATURE?

21. 21
Fig:Yellow color in Yellowstone National Park
Grand Prismatic Spring:due to inhabited by
Sulfolobus acidocaldarius

22. 22
 MICROORGANISM BASED ON TEMPERATURE
REQUIREMENTS

23.  pH = -log[H+]
 Lowest = 0 (very acid); highest = 14 (very basic) Neutral is pH 7.
 Acidophiles/acidotolerant grow at low pH
 Alkalophiles/alkalotolerant grow at high pH
 Most bacteria prefer a neutral pH
23
 MICROORGANISM BASED ON pH

24.  MICROORGANISM BASED ON pH
 Acidophiles: Microorganisms that grow optimally at pH
less than 5.55 are called acidophiles. For example, the
sulfur-oxidizing Sulfolobus spp. isolated from sulfur mud
fields and hot springs in Yellowstone National Park are
extreme acidophiles. These archaea survive at pH values
of 2.5–3.5
 Neutrophiles: Grow best between pH 5.5 and 8.0, Most
familiar bacteria, like Escherichia coli, staphylococci,
and Salmonella spp. are Neutrophiles.
 Alkalophiles: Grow best between pH 8.5 and 11.5 –
Vibrio cholerae, the pathogenic agent of cholera, grows
best at the slightly basic pH of 8.0; it can survive pH
values of 11.0 but is inactivated by the acid of the
stomach.
24

25. 25
Fig:Helicobacter pylori;was identified and isolated by
Barry Marshall and Robin Warren, whose discovery earned
them the Nobel Prize in Medicine in 2005

27. 27
Fig:The sulfur-oxidizing Sulfolobus spp. isolated from sulfur mud
fields and hot springs in Yellowstone National Park are extreme
acidophiles.

28. 28 Figure 3. View from space of Lake Natron in Tanzania. The pink
color is due to the pigmentation of the extreme alkaliphilic and
halophilic microbes that colonize the lake. (credit: NASA)

29. 29

30. MICROBES REQUIREMENT TO DIFFERENT
PRESSURE
 Pressure
 i) Barotolerant organisms are adversely affected by increased
pressure, but not as severely as are non-tolerant organisms
 Ii) Barophilic organisms require, or grow rapidly in the presence of,
increased pressure
 E.g Halomonas salaria requires a pressure of 1000 atm
(100 Mpa).

31.  REFERENCES
 Prescott LM, Harley JP, Klein DA (1996). Microbiology(3rd ed.)
 Powar. and Daginawala. General Microbiology
 : The 2005 Nobel Prize in Physiology or Medicine to Barry J.
Marshall and J. Robin Warren". Nobelprize.org. Nobel Media AB
2014. Web. 28 Oct 2017.
<http://www.nobelprize.org/nobel_prizes/medicine/laureates/2
005/press.
 Tortora GJ, Funke BR, Case CL:
Microbiology An Introduction(8th Ed.)
 Brock TD, Freeze H. Thermus aquaticus gen. n. and sp. n., a
non-sporulating extreme thermophile. Journal of
Bacteriology. 1969;98:289–297. [PMC free article] [PubMed]
 Brock TD. Introduction, an overview of the thermophiles. In:
Brock TD, editor. Thermophiles: General, Molecular and Applied
Microbiology. New York: John Wiley & Sons; 1986. pp. 1–16.
31

32.  Pernilla Turner,1
Gashaw Mamo,1
and Eva Nordberg
Karlsson:Potential and utilization of thermophiles
and thermostable enzymes in biorefining.
 Chen Zhang1,2
and Se-Kwon Kim1,3:
Research and
Application of Marine Microbial Enzymes: Status
and Prospects.
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