Microbial Nutrition Sources of essential nutrients
Chapter 7 Elements of Microbial Nutrition, Ecology, and Growth
Microbial Nutrition
Topics
• Chemical analysis • Sources of essential nutrients • Transport mechanisms
– Microbial Nutrition – Environmental Factors – Microbial Growth
1
2
Bacteria are composed of different elements and molecules, with water (70%) and proteins (15%) being the most abundant.
Sources of essential nutrients • Required for metabolism and growth – Carbon source – Energy source
Analysis of the chemical composition of an E. coli cell.
3
4
1
Defined by Carbon Source
Growth factors
• Heterotroph (depends on other life forms)
• Essential organic nutrients • Not synthesized by the microbe, and must be supplemented • Ex. Amino acids, vitamins
– Organic molecules – Ex. Sugars, proteins, lipids
• Autotroph (self-feeders) – Inorganic molecules – Ex. CO2 5
Energy source
6
Chemoheterotrophs
• Chemoheterotrophs • Photoautotrophs • Chemoautotrophs
• Derive both carbon and energy from organic compounds – Saprobic • decomposers of plant litter, animal matter, and dead microbes
– Parasitic • Live in or on the body of a host
7
8
2
Photoautotroph
Chemo organic autotrophs
• Derive their energy from sunlight • Transform light rays into chemical energy • Primary producers of organic matter for heterotrophs • Primary producers of oxygen • Ex. Algae, plants, some bacteria
• Two types – Chemo organic autotroph • Derives their energy from organic compounds and their carbon source from inorganic compounds
– Lithoautotrophs • Neither sunlight nor organics used, rather it relies totally on inorganics
9
Saprobe mode of action
10
Nutritional categories summary (based on carbon and energy source)
Extracellular digestion in a saprobe with a cell wall.
11
12
3
4 Transport mechanisms • • • •
Osmosis • Diffusion of water through a permeable but selective membrane • Water moves toward the higher solute concentrated areas
Osmosis Diffusion Active transport Endocytosis
– Isotonic – Hypotonic – Hypertonic 13
14
Diffusion Facilitated diffusion • Net molecule movement from high concentration area to low concentration area • No energy is expended (passive) • Concentration gradient and permeability affect movement
• Transport of polar molecules and ions across the membrane • No energy is expended (passive) • Carrier protein facilitates the binding and transport – Specificity – Saturation – Competition 15
16
4
Active transport
Endocytosis
• Transport of molecules against a gradient • Requires energy (active) • Ex. Permeases and protein pumps transport sugars, amino acids, organic acids, phosphates and metal ions. • Ex. Group translocation transports and modifies specific sugars
• Substances are taken, but are not transported through the membrane. • Requires energy (active) • Common for eucaryotes • Ex. Phagocytosis, pinocytosis
17
18
Cell transport process summary
Active transport examples permease
group translocation
endocytosis
19
20
5
Environmental Factors • • • • • •
Temperature optimal growth and metabolism: • Psychrophile – 0 to 15 °C • Mesophile – 20 to 40 °C • Thermophile45 to 80 °C
Temperature Gas pH Osmotic pressure Other factors Microbial association 21
Gas
22
Oxidizing agent
• Two gases that most influence microbial growth – Oxygen • Respiration • Oxidizing agent (adds O2 to a compound with a loss of electrons)
• Oxygen metabolites are toxic • These toxic metabolites must be neutralized for growth • Three categories of bacteria – Obligate aerobe – Facultative anaerobe – Obligate anaerobe
– Carbon dioxide 23
24
6
Obligate aerobe
Facultative anaerobe • Does not require oxygen for metabolism, but can grow in its presence • During minus oxygen states, anaerobic respiration or fermentation occurs • Possess superoxide dismutase and catalase • Ex. Gram negative pathogens
• Requires oxygen for metabolism • Possess enzymes that can neutralize the toxic oxygen metabolites – Superoxide dismutase and catalase
• Ex. Most fungi, protozoa, and bacteria
25
26
Thioglycollate broth shows aerobes, facultative anaerobes, and obligate anaerobes.
Obligate anaerobes • Cannot use oxygen for metabolism • Do not possess superoxide dismutase and catalase • The presence of oxygen is toxic to the cell
27
28
7
pH
Osmotic pressure
• Cells grow best between pH 6-8 • Exceptions would be acidophiles (pH 0), and alkalinophiles (pH 10).
• • • • •
Halophiles Requires high salt concentrations Withstands hypertonic conditions Ex. Halobacterium Facultative halophiles – Can survive high salt conditions but is not required – Ex. Staphylococcus aureus
29
Other factors
30
Ecological association
• Radiation- withstand UV, infrared • Barophiles – withstand high pressures • Spores and cysts- can survive dry habitats
• Influence microorganisms have on other microbes – Symbiotic relationship – Non-symbiotic relationship
31
32
8
3 Types of Symbiotic Relationships
2 Types of Non-symbiotic Relationships
Symbiotic: Organisms that live in close nutritional relationship
Non-symbiotic: Organisms are free-living, and do not rely on each other for survival
• Types
• Types
– Mutualism – both organism benefit – Commensalism – one organisms benefits – Parasitism – host/microbe relationship
– Synergism – shared metabolism, not required – Antagonism- competition between microorganisms
33
34
Interrelationships between microbes and humans
Microbial Growth
• Can be commensal, parasitic, synergistic • Ex. E. coli produce vitamin K for the host
• • • •
35
Binary fission Generation time Growth curve Enumeration of bacteria
36
9
Binary fission
Generation time
• The division of a bacterial cell • Parental cell enlarges and duplicates its DNA • Septum formation divides the cell into two separate chambers • Complete division results in two identical cells
• The time required for a complete division cycle (doubling) • Length of the generation time is a measure of the growth rate • Exponentials (logs) used to define numbers of bacteria
37
38
Mathematics of population growth from a single bacterium
Growth curve • • • •
# of bacteria = 2n , where n = the # of divisions
39
Lag phase Log phase Stationary phase Death phase
40
10
Enumeration of bacteria • Turbidity • Direct cell count • Automated devices – Coulter counter – Flow cytometer – Real-time PCR
41
11
Microbial Nutrition
Topics
• Chemical analysis • Sources of essential nutrients • Transport mechanisms
– Microbial Nutrition – Environmental Factors – Microbial Growth
1
2
Bacteria are composed of different elements and molecules, with water (70%) and proteins (15%) being the most abundant.
Sources of essential nutrients • Required for metabolism and growth – Carbon source – Energy source
Analysis of the chemical composition of an E. coli cell.
3
4
1
Defined by Carbon Source
Growth factors
• Heterotroph (depends on other life forms)
• Essential organic nutrients • Not synthesized by the microbe, and must be supplemented • Ex. Amino acids, vitamins
– Organic molecules – Ex. Sugars, proteins, lipids
• Autotroph (self-feeders) – Inorganic molecules – Ex. CO2 5
Energy source
6
Chemoheterotrophs
• Chemoheterotrophs • Photoautotrophs • Chemoautotrophs
• Derive both carbon and energy from organic compounds – Saprobic • decomposers of plant litter, animal matter, and dead microbes
– Parasitic • Live in or on the body of a host
7
8
2
Photoautotroph
Chemo organic autotrophs
• Derive their energy from sunlight • Transform light rays into chemical energy • Primary producers of organic matter for heterotrophs • Primary producers of oxygen • Ex. Algae, plants, some bacteria
• Two types – Chemo organic autotroph • Derives their energy from organic compounds and their carbon source from inorganic compounds
– Lithoautotrophs • Neither sunlight nor organics used, rather it relies totally on inorganics
9
Saprobe mode of action
10
Nutritional categories summary (based on carbon and energy source)
Extracellular digestion in a saprobe with a cell wall.
11
12
3
4 Transport mechanisms • • • •
Osmosis • Diffusion of water through a permeable but selective membrane • Water moves toward the higher solute concentrated areas
Osmosis Diffusion Active transport Endocytosis
– Isotonic – Hypotonic – Hypertonic 13
14
Diffusion Facilitated diffusion • Net molecule movement from high concentration area to low concentration area • No energy is expended (passive) • Concentration gradient and permeability affect movement
• Transport of polar molecules and ions across the membrane • No energy is expended (passive) • Carrier protein facilitates the binding and transport – Specificity – Saturation – Competition 15
16
4
Active transport
Endocytosis
• Transport of molecules against a gradient • Requires energy (active) • Ex. Permeases and protein pumps transport sugars, amino acids, organic acids, phosphates and metal ions. • Ex. Group translocation transports and modifies specific sugars
• Substances are taken, but are not transported through the membrane. • Requires energy (active) • Common for eucaryotes • Ex. Phagocytosis, pinocytosis
17
18
Cell transport process summary
Active transport examples permease
group translocation
endocytosis
19
20
5
Environmental Factors • • • • • •
Temperature optimal growth and metabolism: • Psychrophile – 0 to 15 °C • Mesophile – 20 to 40 °C • Thermophile45 to 80 °C
Temperature Gas pH Osmotic pressure Other factors Microbial association 21
Gas
22
Oxidizing agent
• Two gases that most influence microbial growth – Oxygen • Respiration • Oxidizing agent (adds O2 to a compound with a loss of electrons)
• Oxygen metabolites are toxic • These toxic metabolites must be neutralized for growth • Three categories of bacteria – Obligate aerobe – Facultative anaerobe – Obligate anaerobe
– Carbon dioxide 23
24
6
Obligate aerobe
Facultative anaerobe • Does not require oxygen for metabolism, but can grow in its presence • During minus oxygen states, anaerobic respiration or fermentation occurs • Possess superoxide dismutase and catalase • Ex. Gram negative pathogens
• Requires oxygen for metabolism • Possess enzymes that can neutralize the toxic oxygen metabolites – Superoxide dismutase and catalase
• Ex. Most fungi, protozoa, and bacteria
25
26
Thioglycollate broth shows aerobes, facultative anaerobes, and obligate anaerobes.
Obligate anaerobes • Cannot use oxygen for metabolism • Do not possess superoxide dismutase and catalase • The presence of oxygen is toxic to the cell
27
28
7
pH
Osmotic pressure
• Cells grow best between pH 6-8 • Exceptions would be acidophiles (pH 0), and alkalinophiles (pH 10).
• • • • •
Halophiles Requires high salt concentrations Withstands hypertonic conditions Ex. Halobacterium Facultative halophiles – Can survive high salt conditions but is not required – Ex. Staphylococcus aureus
29
Other factors
30
Ecological association
• Radiation- withstand UV, infrared • Barophiles – withstand high pressures • Spores and cysts- can survive dry habitats
• Influence microorganisms have on other microbes – Symbiotic relationship – Non-symbiotic relationship
31
32
8
3 Types of Symbiotic Relationships
2 Types of Non-symbiotic Relationships
Symbiotic: Organisms that live in close nutritional relationship
Non-symbiotic: Organisms are free-living, and do not rely on each other for survival
• Types
• Types
– Mutualism – both organism benefit – Commensalism – one organisms benefits – Parasitism – host/microbe relationship
– Synergism – shared metabolism, not required – Antagonism- competition between microorganisms
33
34
Interrelationships between microbes and humans
Microbial Growth
• Can be commensal, parasitic, synergistic • Ex. E. coli produce vitamin K for the host
• • • •
35
Binary fission Generation time Growth curve Enumeration of bacteria
36
9
Binary fission
Generation time
• The division of a bacterial cell • Parental cell enlarges and duplicates its DNA • Septum formation divides the cell into two separate chambers • Complete division results in two identical cells
• The time required for a complete division cycle (doubling) • Length of the generation time is a measure of the growth rate • Exponentials (logs) used to define numbers of bacteria
37
38
Mathematics of population growth from a single bacterium
Growth curve • • • •
# of bacteria = 2n , where n = the # of divisions
39
Lag phase Log phase Stationary phase Death phase
40
10
Enumeration of bacteria • Turbidity • Direct cell count • Automated devices – Coulter counter – Flow cytometer – Real-time PCR
41
11
