Download metabolism of lipids

Study of the biochemical activity of bacteria
Omid Tadayoun
supervised: berzsu
METABOLISM OF LIPIDS,
AMINO ACIDS AND OTHER
NITROGEN CONTAINING
COMPOUNDS
METABOLISM OF LIPIDS
|
Phospholipase
y
|
An enzyme that hydrolyzes phospholipids into fatty
acids and other lipophilic substances
Lipase
An enzyme that catalyzes the hydrolysis of fats into
glycerol and fatty acids
y Facilitate nutrient absorption from the external medium
y In pathogenic microbes, it may promote invasion of a
new host
y
|
Lecithinase
y
Type of phospholipid that acts upon lecithin.
METABOLISM OF LIPIDS
|
Lecithinase
y
y
y
y
y
Can be demonstrated on egg-yolk medium
Egg yolk consists of lecithin
Lecitinase cleaves lecithin into diglyceride +
phosphorylcholine
Opalescent part around the colonies
Bacillus cereus, Clostridium perfringens (Nagler test)
LECITHINASE TEST
Lecithin positive
B. cereus
Lecithin negative
B. sphaericus
METABOLISM OF AMINO ACIDS AND OTHER
NITROGEN CONTAINING COMPOUNDS
Urea breakdown
| H2S production
| Indole production
|
METABOLISM OF AMINO ACIDS AND OTHER
NITROGEN CONTAINING COMPOUNDS
|
Urea breakdown
y
y
y
y
y
Christensen medium. slant, solid medium containing
urea, dextrose, phenol-red indicator
Urease +. urease releases ammonia from the urea,
ammonia increases the pH, color of the indicator
changes into purple
Urease -. dextrose utilized, producing acid, decreasing
the pH, coloring the medium yellow
Originally the color of the medium is dark yellow/orange
E.g. Helicobacter pylori; some Proteus sp.; some
Klebsiella sp.
UREASE TEST
Urease -
Urease +
METABOLISM OF AMINO ACIDS AND OTHER
NITROGEN CONTAINING COMPOUNDS
|
H2S production
y
y
y
y
y
y
y
y
often results from the bacterial breakdown of sulfites in
non-organic matter in the absence of oxygen
H2S is produces from thiosulfate
Indicators: heavy metal salts formed -> black color
Lead nitrate in agar traps H2S, forming a black
precipitant when lead sulfide is formed
Bismuth sulfite medium
Iron-high agar
Agar turns black when H2S +, no color change when
H2S –
E.g. Salmonella sp; some Proteus sp.
wqc.arizona.edu
H2S PRODUCTION
Salmonella on Bismuth sulfite agar
METABOLISM OF AMINO ACIDS AND OTHER
NITROGEN CONTAINING COMPOUNDS
|
Indole production
y
y
y
y
y
Tryptophanase enzyme activity is seen
Free indole ring is generated by deamination from
tryptophan, by the enzyme tryptophanase
Kovacs´ (Erlich) reagent (containing free aldehyde
group) will react with the indole-ring to form a bright red
ring at the surface of the tube
Final products of the reaction are indole, pyruvic acid,
ammonia
E.g. Escherichia coli; some Proteus sp.
INDOLE TEST
Indole +
Indole -