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PowerPoint to accompany
Foundations in Microbiology
Fifth Edition
Talaro
Chapter
7
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Elements of Microbial Nutrition,
Ecology and Growth
Chapter 7
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
3
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
4
Chemical composition of cytoplasm
• 70% water
• proteins
• 96% of cell is composed of 6 elements
–
–
–
–
–
Carbon
Hydrogen
Oxygen
Phosphorous
Sulfur
5
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
6
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.
7
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
8
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 oxidationreduction reactions of respiration
9
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)
10
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
11
Important mineral ions
•
•
•
•
•
Potassium
Sodium
Calcium
Magnesium
Iron
12
Growth factors
• organic compounds that cannot be synthesized
by an organism & must be provided as a
nutrient
– essential amino acids, vitamins
13
Carbon
source
Energy source
photoautotrophs
CO2
sunlight
chemoautotrophs
CO2
Simple inorganic
chemicals
photoheterotrophs
organic
sunlight
chemoheterotrophs
organic
Metabolizing
organic cpds
14
• Saprobes – decompose dead organisms,
recycle elements, release enzymes to digest
materials
• Parasites – utilize tissues and fluids of a living
host and cause harm
15
saprobes
16
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
17
diffusion
18
osmosis
19
20
passive transport
21
Active transport
22
Bulk transport
23
Environmental influences on
microbial growth
•
•
•
•
•
temperature
oxygen requirements
pH
electromagnetic radiation
barometric pressure
24
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
25
3 temperature adaptation groups
1. Psychrophiles – optimum temperature below
15oC, capable of growth at 0oC
2. Mesophiles – optimum temperature 20o40oC, most human pathogens
3. Thermophiles – optimum temperature
greater than 45oC
26
3 temperature adaptation groups
27
Oxygen requirements
28
29
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
30
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
31
Binary Fission
32
Population growth
33
Growth curve
34
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
35
Turbidity
36
Direct microscopic count
37
Electronic counting
38