prof . dr. ihsan edan alsaimary department of microbiology - college of medicine - university of basrah - basrah -IRAQ ihsanalsaimary@gmail.com 00964 7801410838

1. Microbial nutrition,
and nutritional requirements
3rd lecture
prepared by
Dr. Ihsan edan alsaimary
Professor
department of microbiology – college of medicine –
university of basrah - iraq

2. Objectives of the lecture
1-define microbial nutrition
2- determine the types of nutrients
3- classify the microorganisms depend on the
types of nutrition
4-discuss the importance of each nutrients in
the livuiing of microorganisms
5- clarify physicochemical factors affecting
on microorganisms life

3. nutrition
process by which chemical substances
(nutrients) are acquired from the
environment and used for cellular activities
essential nutrients
must be provided to an organism
Two categories of essential nutrients:
macronutrients
micronutrients or trace elements

4. • macronutrients
– required in large quantities
– role in cell structure and metabolism
– Ex: proteins, carbohydrates
• micronutrients or trace elements
– required in small amounts
– involved in enzyme function and maintenance of
protein structure
– Ex: manganese, zinc, nickel

5. Nutrients
• Inorganic nutrients
– atom or molecule that contains a combination of atoms
other than carbon and hydrogen
– metals and their salts (magnesium sulfate, ferric nitrate,
sodium phosphate), gases (oxygen, carbon dioxide) and
water
• Organic nutrients
– contain carbon and hydrogen atoms and are usually the
products of living things
– methane (CH4), carbohydrates, lipids, proteins, and nucleic
acids

6. Chemical Composition
of bacterial Cytoplasm
• 70% water
• Proteins
• 96% of cell is
• composed of 6 elements:
– Carbon
– Nitrogen
– Oxygen
– Hydrogen
– Phosphorous
– Sulfur

7. The Requirements for Growth
• Physical requirements
• 1-temperature,
• 2-pH
• 3-Oxygen requirement
• 4-osmotic pressure (water)
5-Hydrostatic pressure
6-Radiation
• Chemical requirements
carbon, oxygen, nitrogen, sulfur, phosphorus,
trace elements, and organic growth factors

8. Growth Factors
organic compounds that cannot be
synthesized by an organism & must
be provided as a nutrient
such as
essential amino acids, vitamins ,
nitrogen bases, others

9. Obtaining Carbon
• Heterotroph
– organism that obtains carbon in an organic form
made by other living organisms
– proteins, carbohydrates, lipids and nucleic acids
• Autotroph
– an organism that uses CO2 (an inorganic gas) as
its carbon source
– not dependent on other living things

10. Classification of microorganisms according
to carbon sources and energy sources:
• Nutritional types
– Chemo-
• Chemical compounds
– Photo-
• light
Name of group Carbon
source
Energy
source
Photoautotrophs
( autotrophs)
CO2 sunlight
chemoautotrophs CO2 Simple
inorganic
chemicals
photoheterotrophs organic sunlight
Chemoheterotrophs
(Heterotrophs)
organic Metabolizing
organic cmpds

11. Other Heterotrophs
• Saprobes
– decompose dead
organisms
– recycle elements
– release enzymes to
digest materials
• Parasites
– utilize tissues and fluids
of a living host
– cause harm

12. Environmental Influences on
Microbial Growth
• 1. temperature
• 2. oxygen requirements
• 3. pH
• 4. Osmotic pressure
• 5. radiation
• 6. hydrostatic pressure

13. 1-Temperature
1. Psychrophiles
• optimum temperature below
15oC, capable of growth at 0oC
• Examples are Arthrobacter sp.,
Psychrobacter sp. and members of the
genera Halomonas, Pseudomonas,
Hyphomonas, and Sphingomonas.
2. Mesophiles
• optimum temperature 20o-40oC,
• EX: most human pathogens
3. Thermophiles
• optimum temperature greater
than 45oC
• Ex: Thermus aquaticus

14. Physiological adaption at High temperature-
modification by thermophiles
• Relative greater conc. of guanine & cytosine in
DNA & RNA
• GC base pair involve in three hydrogen bonds
making them more stable at high temperature
than AT base pair that form only two hydrogen
bond
• Stability of DNA & RNA is critical to cell
survival
• Enzymes thermally stable
• high conc. of hydrophobic Amino acid
• Cytoplasmic membrane is modified
• high proportion of high molecular weight
saturated fatty acid.

15. 2-Oxygen Requirement
• molecular oxygen (O2) as a necessity of life,
but it is actually in a sense a poisonous gas
• metabolic systems require oxygen for
aerobic respiration
• Microbes that use molecular oxygen
(aerobes) produce more energy from
nutrients than microbes that do not use
oxygen (anaerobes)
• superoxide dismutase (SOD), catalase,
hydrogen peroxidase
• Enzymes which neutralize toxic oxygen

16. 2. Oxygen Requirements
• Aerobe
– requires oxygen
• Obligate aerobe
– cannot grow without oxygen
• Facultative anaerobe
– capable of growth in the
absence OR presence of
oxygen
• Microaerophile
– does not grow at normal
atmospheric tensions of
oxygen
– i.e., the soil, water or the
human body
– EX: Helicobacter pylori &
Campylobacter & Borrelia

17. 2. Oxygen Requirements
• Anaerobe
– does not require oxygen
– Ex: Clostridium
• Capnophiles
– Need Higher conc. Of CO2
– Ex: Erysipelothrix
• Aerotolerant anaerobes
– does not utilize oxygen but can
survive and grow to limited extent
in its presence
– Ex: Peptostreptococcus &
Bateroides

19. 3. pH
• Alkaliphiles
– optimum pH is relatively to
highly basic
• Ex: Bacillus okhensis &
• Alkalibacterium iburiense
• Neutrophiles
– optimum pH ranges about
pH 7 (plus or minus)
• Ex: human pathogens
• Acidophiles
– optimum pH is relatively to
highly acidic
– Ex: Acidobacterium &
Thiobacillus

20. 4-Osmotic Pressure
• Microorganisms obtain almost all their nutrients in solution from the
surrounding water
• Osmotic pressure – water diffusing across cell membrane in response
to solute conc.
• Bacteria 80% water
• Require water to grow
• Xerophiles are extremophilic organisms that can grow and reproduce
in conditions with a low availability of water, Xerophiles are often said
to be "xerotolerant", meaning tolerant of dry conditions. They can
survive in environments with water activity below 0.8.
• Endoliths and halophiles are often xerotolerant.
• Ex: Trichosporonoides nigrescens
• extreme or obligate halophiles
• Adapted to and require high salt concentrations
• Ex: Halococcus & Halobacterium

21. 5. Radiation
1-short wave length ,high eneregy radiation
2-larg wave length , low eneregy radiation
• Radioresistance is the property of
microorganisms that are capable of
living in environments with very high
levels of ionizing radiation.
ex:Deinococcus radiodurans
• Great for killing bacteria
• Damages the DNA (making thymine dimers)
– in sufficient quantity can kill the organisms
– in a lower range causes mutagenesis
– Cause melanoma or xeroderma pigmentosa
• Spores tend to be resistant
– can survive much longer exposures

22. 6. Barophiles(piezophile)
• is an organism which thrives at high
pressures, such as deep sea bacteria
or archaea. They are generally found
on ocean floors, where pressure often
exceeds 380 atm (38 MPa
• Bacteria that grow at moderately high
hydrostatic pressures
– Oceans
• Barotolerants
– Grows at pressures from 100-500 Atm
– Ex: Bacillus subtilis
• Barophilic
– 400-500
– Ex: Xenophyophores
• Extreme barophilic
– Higher than 500
– Ex: Halomonas salaria