Microbial nutrition requires both macronutrients like proteins and carbohydrates, and micronutrients like manganese and zinc. Microbes obtain carbon and nitrogen from organic and inorganic sources, with oxygen, hydrogen, phosphorus, and sulfur playing important structural and metabolic roles within cells. Microbial growth is influenced by temperature, oxygen requirements, pH, and other environmental factors. Microbes can exist in symbiotic or non-symbiotic relationships and reproduce through binary fission and population growth follows a characteristic growth curve pattern.

1. Foundations in Microbiology
Chapter
7
PowerPoint to accompany
Fifth Edition
Talaro
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Elements of Microbial Nutrition,
Ecology and Growth
Chapter 7

3. 3
Microbial nutrition
• Macronutrients – required in large quantities;
play principal roles in cell structure &
metabolism
– proteins, carbohydrates
• Micronutrients or trace elements – required
in small amounts; involved in enzyme function
& maintenance of protein structure
– manganese, zinc, nickel

4. 4
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

5. 5
Chemical composition of cytoplasm
• 70% water
• proteins
• 96% of cell is composed of 6 elements
– Carbon
– Hydrogen
– Oxygen
– Phosphorous
– Sulfur

6. 6
Obtaining Carbon
• Heterotroph – an organism that must obtain
carbon in an organic form made by other
living organisms such as 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

7. 7
Nitrogen
• Main reservoir is nitrogen gas (N2)
• 79% of earth’s atmosphere is N2
• Nitrogen is part of the structure of proteins, DNA,
RNA & ATP – these are the primary source of N for
heterotrophs
• Some bacteria & algae use inorganic N nutrients
(NO3
-
, NO2
-
, or NH3)
• Some bacteria can fix N2
• Regardless of how N enters the cell, it must be
converted to NH3, the only form that can be combined
with carbon to synthesis amino acids, etc.

8. 8
Oxygen
• major component of carbohydrates, lipids and
proteins
• plays an important role in structural &
enzymatic functions of cell
• component of inorganic salts (sulfates,
phosphates, nitrates) & water
• O2 makes up 20% of atmosphere
• essential to metabolism of many organisms

9. 9
Hydrogen
• major element in all organic compounds &
several inorganic ones (water, salts & gases)
• gases are produced & used by microbes
• roles of hydrogen
– maintaining pH
– forming H bonds between molecules
– serving as the source of free energy in oxidation-
reduction reactions of respiration

10. 10
Phosphorous
• main inorganic source is phosphate (PO4
-3
)
derived from phosphoric acid (H3PO4) found in
rocks & oceanic mineral deposits
• key component of nucleic acids, essential to
genetics
• serves in energy transfers (ATP)

11. 11
Sulfur
• widely distributed in environment, rocks,
sediments contain sulfate, sulfides, hydrogen
sulfide gas and sulfur
• essential component of some vitamins and the
amino acids: methionine & cysteine
• contributes to stability of proteins by forming
disulfide bonds

12. 12
Important mineral ions
• Potassium
• Sodium
• Calcium
• Magnesium
• Iron

13. 13
Growth factors
• organic compounds that cannot be synthesized
by an organism & must be provided as a
nutrient
– essential amino acids, vitamins

14. 14
Carbon
source
Energy source
photoautotrophs CO2 sunlight
chemoautotrophs CO2 Simple inorganic
chemicals
photoheterotrophs organic sunlight
chemoheterotrophs organic Metabolizing
organic cpds

15. 15
• Saprobes – decompose dead organisms,
recycle elements, release enzymes to digest
materials
• Parasites – utilize tissues and fluids of a living
host and cause harm

16. 16
saprobes

17. 17
Transport mechanisms
• Passive transport –do not require energy, substances
exist in a gradient and move from areas of higher
concentration towards areas of lower concentration
– Diffusion
– Osmosis - water
– Facilitated diffusion – requires a carrier
• Active transport – require energy and carrier proteins,
gradient independent
– Carrier-mediated active transport
– Group translocation – transported molecule
chemically altered
– Bulk transport – endocytosis, exocytosis, pinocytosis

18. 18
diffusion

19. 19
osmosis

20. 20

21. 21
passive transport

22. 22
Active transport

23. 23
Bulk transport

24. 24
Environmental influences on
microbial growth
• temperature
• oxygen requirements
• pH
• electromagnetic radiation
• barometric pressure

25. 25
3 cardinal temperatures
• Minimum temperature – lowest temperature
that permits a microbe’s growth and
metabolism
• Maximum temperature – highest
temperature that permits a microbe’s growth
and metabolism
• Optimum temperature – promotes the fastest
rate of growth and metabolism

26. 26
3 temperature adaptation groups
1. Psychrophiles – optimum temperature
below 15o
C, capable of growth at 0o
C
2. Mesophiles – optimum temperature 20o
-40o
C,
most human pathogens
3. Thermophiles – optimum temperature
greater than 45o
C

27. 27
3 temperature adaptation groups

28. 28
Oxygen requirements

29. 29

30. 30
Microbial associations
• Symbiotic – organisms live in close nutritional
relationships; required by one or both
members
– Mutualism – obligatory, dependent; both
members benefit
– Commensalism – commensal member benefits,
other member not harmed
– Parasitism – parasite is dependent and benefits;
host is harmed

31. 31
Microbial associations
• Non-symbiotic – organisms are free-living;
relationships not required for survival
– Synergism – members cooperate and share
nutrients
– Antagonism – some member are inhibited or
destroyed by others

32. 32
Binary Fission

33. 33
Population growth

34. 34
Growth curve

35. 35
Growth curve
1. Lag phase – “flat” period of adjustment, enlargement;
little growth
2. Exponential growth phase – a period of maximum
growth will continue as long as cells have adequate
nutrients & a favorable environment
3. Stationary phase – rate of cell growth equals rate of cell
death cause by depleted nutrients & O2, excretion of
organic acids & pollutants
4. Death phase – as limiting factors intensify, cells die
exponentially in their own wastes

36. 36
Turbidity

37. 37
Direct microscopic count

38. 38
Electronic counting