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BACTERIAL METABOLISM
Bacterial Metabolism
Metabolism
– Sum up all the chemical processes that occur within a cell
1. Anabolism: Synthesis of more complex compounds and use of energy
2. Catabolism: Break down a substrate and capture energy
All microbial metabolisms can be arranged according to three principles:
1. obtaining carbon for synthesis
– Autotrophic: carbon is obtained from CO2
– Heterophic: Corbon is obtained from organic compounds
All microbial metabolisms can be arranged according to three principles:
• 2. Obtaining reducing equivalents for enegry conservation and synthesis
– Lithotrophic: reducing equivalents are obtained from inorganic compounds
– Organotrophic: reducing equivalents are obtained from inorganic compounds
All microbial metabolisms can be arranged according to three principles:
• 3. Source of the energy
– Chemotrophic: energy is obtained from external sources
– Phototrophic: energy is obtained from light by photosynthesis
Biochemical tests can be used for the identification of the bacteria
1. Oxidase Test
2. Catalase Test
3. Fermentation tests: Glucose, lactose, sucrose,…….
4. Enzyme tests: urease, tryptophan deaminase, DNase,….
5. Utilization tests: Citrate, malonate, asetate
6. Decorboxylation tests: Lysine, Arginine, Ornitine
7. Hydrolysis tests: Gelatin, esculin
8. Others: H2S production, motility, growth in KCN,….
Catalase test
Streptococci
Staphylococci
Oxidase test
Positive Negative
P. aeruginosa E. coli
Lactose fermentation
On the front bench
Oxidase test Catalase test
.
Citrate medium
Pseudomonas
E. coli
Klebsiella
Urease medium
E. coli Proteus
Oxidative Fermentative medium
On every bench
Triple Sugar Iron Agar
Pseudomonas
E. coli
Proteus
Pseudomonas
Inoculation to Fermentation medium
Inoculation to Urease medium and Citrate medium
Urea agar Citrate agar
Inoculation to the Triple Sugar Iron Agar (TSIA)
Fermentation medium
Urea agar Citrate agar
1
2
TSIA
Don’t tighten the cap of the tube
BACTERIAL METABOLISM II
Oxidation-Fermentation Test (OF test)
Carbohydrate (Glucose)
Bromthymol blue (pH indicator)
Mineral oil
(anaerobic environment)
Mineral oil
(anaerobic environment)
Glucose fermentation
Acid production
pH of the medium
pH indicator
green yellow
Gas production-Durham tube
Glucose fermentation (-) Glucose fermentation (+)
Glucose fermentation
Acid production
pH of the medium doesn’t change.
pH indicator
green
Fermentative
Oxidative
Non-fermentative
Oxidative
Non-fermentative
Non-oxidative
Urease Test
Urea agar:
Urea
Phenol red (pH indicator)
Urea agar
Urea
Ammonia + CO2
pH
Urease
pH indicator
yellow pink
Urease (+) Urease (-)
Urea
Urease
The pH of the medium doesn’t change.
pH indicator
yellow
Citrate utilization
Citrate medium
Citrate medium:
Citrate (Carbon source)
Ammonium salts (Nitrogen source)
Bromthymol blue (pH indicator)
Citrate utilization
Ammonium salts
Ammonia (pH )
pH indicator
green blue
Citrate(+) Citrate (-)
Citrate utilization
Ammonium salts
No ammonia production
pH doesn’t change.
pH indicator
green
Triple Sugar Iron Agar (TSI)
Glucose %1
Lactose %10 Acid and gas production
Sucrose %10
Phenol red (pH indicator)
Sodium thiosulfate (-S source)
Ferrous sulfate (H2S indicator)
Peptone (N source-Oxydation) Triple Sugar Iron Agar
(TSI)
Acid-gas and H2S production
Only glucose fermentation
Glucose (%1) fermentation
Acid production
The pH of the medium
pH indicator
Red yellow
Peptids amines
pH of the slant
pH indicator
red pink
Glucose and lactose and / or sucrose fermentation
Gas production
Glucose and lactose and/or sucrose fermentation
Acid production
The pH of the medium
pH indicator
red yellow
Nonfermentative bacteria
Carbohydrate fermentation (-)
pH of the medium doesn’t change.
The colour of the medium remains same
Peptids amines O2
pH
pH indicator
Red pink
H2S production
Thiosulfate (sulfur source)
H2S
H2S + ferrous sulfate (H2S indicator)
Ferric sulfide
(black precipitate)
Enzymatic activation
Automated System depends on biochemical and metabolic reactions
