Nutrition, Growth and Metabolism,
Lecture 26
Dr. Alvin Fox
1
KEY TERMS
Obligate aerobe
Obligate anaerobe
Aerotolerant anaerobe
Facultative anaerobe
Microaerophilic
Siderophore
Mesophile
Thermophile
Psychrophile
Generation time
Growth curve
Glycolysis
Fermentation
Anaerobic respiration
Aerobic respiration
Tricarboxylic acid (TCA)
cycle or Krebs cycle
Oxidative phosphorylation
Ubiquinone
Glyoxylate pathway
2
Bacterial requirements for growth
•
•
•
•
•
oxygen (or absence)
energy
nutrients
optimal temperature
optimal pH
3
Obligate aerobes
• grow in presence of oxygen
• no fermentation
• oxidative phosphorylation
4
•
•
•
•
Obligate anaerobes
no oxidative phosphorylation
fermentation
killed by oxygen
lack certain enzymes:
superoxide dismutase
O2-+2H+
H2O2
catalase
H2O2
H20 + O2
peroxidase
H2O2 + NADH + H+
H20 + NAD
5
Aerotolerant anaerobes
• respire anaerobically
• not killed by oxygen
6
Facultative anaerobes
• fermentation
• aerobic respiration
• survive in oxygen
7
Microaerophilic bacteria
• grow
– low oxygen
• killed
– high oxygen
8
Optimal growth temperature
• Mesophiles:
– human body temperature
* pathogens
* opportunists
• pyschrophile
– close to freezing
• thermophile
– close to boiling
9
pH
• Many grow best at neutral pH
• Some can survive/grow
- acid
- alkali
10
Nutrient Requirements
•
•
•
•
•
Carbon
Nitrogen
Phosphorus
Sulfur
Metal ions (e.g. iron)
11
Siderophores (S)
Receptor
Fe 2+/S
Fe 2+/S
12
Measuring bacterial mass (live + dead)
in liquid culture
Turbidity
(Cloudiness)
13
Measuring viable bacteria
Colony forming units
colony
14
Growth Curve
Stationary
TURBIDITY
(cloudiness)
Autolysis
Log
Lag
TIME
15
Growth Curve
Stationary
COLONY
FORMING
UNITS
Death
Log
Lag
TIME
16
Generation time
• time for bacterial mass to double
• Example
100 bacteria present at time 0
If generation time is 2 hr
After 8 hr mass = 100 x 24
17
SUGAR CATABOLISM
• Glycolysis
– Embden Meyerhof Parnas Pathway
– most bacteria
– also animals and plants
18
Other pathways for catabolizing
sugars
• Pentose phosphate pathway (hexose
monophosphate shunt)
– generates NADPH
– common in plants and animals
• Entner Doudoroff Pathway
– a few bacterial species
19
Glycolysis
NAD
NADH
Glucose
Pyruvate
C6
C3
ADP
ATP
20
Fermentation
NADH
Pyruvate
NAD
Short chain alcohols,
fatty acids
(C3)
(C2-C4)
21
Anaerobic Respiration =
Glycolysis + Fermentation
NAD
NADH
ATP
NADH
NAD
22
Krebs Cycle (C4-C6 intermediate compounds)
NAD
Pyruvate
NADH
3CO2
(C3)
(C1)
Oxidative phosphorylation
NADH
NAD
O2
H2O
ADP
ATP
23
Aerobic Respiration =
Glycolysis +
Krebs Cycle/oxidative phosphorylation
•
Pyruvate to CO2
–
NAD to NADH
–
glycolysis
– Krebs cycle
•
Oxidative phosphorylation
–
NADH to NAD
– ADP to ATP
24
Oxidative phosphylation
• converts O2 to H20 (oxidative)
• converts ADP to ATP (phosphorylation)
• electron transport chain
• ubiquinones/cytochrome intermediates
25
The Krebs cycle
-CO2
C2
Acetate Citrate
Isocitrate
C6
+
C
X
-CO2 NADH
Alpha-keto
glutarate
Oxaloacetate C4
-CO2 NADH
Pyruvate
x
Succinate C
Malate
Fumarate
26
Krebs Cycle - sugar as sole
carbon source
-CO2
Pyruvate
C3
C
Acetate +
Oxalo
C2
C4 acetate
X
+ CO2
Pyruvate
C3
C
Citrate
C6
-2CO2
BIOSYNTHESIS
Oxalo
acetate
Krebs
cycle
ENERGY
STORAGE
Aspartic acid
Oxaloacetate
C4
27
Krebs Cycle – fatty acids as
sole carbon source
ENERGY
Acetate
+ Oxalo
acetate
BIOSYNTHESIS
Fatty acids
x
Oxalo
acetate
Krebs
cycle
Citrate
-2CO2
Aspartic acid
C2
Isocitrate
Succinate + Glyoxylate
-2CO2
C6 Krebs cycle
C2
+ Acetate
C4
Malate
28
C4
The Glyoxylate and Krebs cycles
Isocitrate
Citrate
Oxaloacetate
Malate
1
Glyoxylate
2
+ Acetate
Alpha-keto
glutarate
Succinate
Fumarate
Krebs and Glyoxylate cycles
Krebs cycle only
Glyoxylate cycle only
29
Krebs Cycle
– biosynthetic
– energy storage
• Removal of intermediates
– must be replenished
• Unique enzymatic replenishment pathways
– sugars
– fatty acids
30