2.  Primary metabolism: known function
 Example of primary metabolites:
 Pyruvate
 Ethanol
 Lactic acid
 Primary metabolism is used for:
 Growth and development of hyphal structure
 Energy metabolism
 Regulation of metabolism
 Intermediate in biosynthesis of compound
 Widely distributed in nature

3.  Often lack known function
 Found in few species or genera
 Specialised distribution peculiar to individual species or
small groups of species: idiosynchratic- very
unique, special and specific
 Production of these compounds often after growth has
stopped. Why?
- limitation/nutrients depression
- Contamination- competition
- Fungal cell death due to physical and chemical factors

4. Primary metabolism Secondary metabolism
Function are known Function are usually unknown- lack
Widely distributed in nature Only found in few species or genera -
idiosynchratic
Usually used for growth, energy and as
intermediate
Produced usually after growth has
stopped
Examples: Pyruvate, lactic acid, ethanol Examples:
Penicillin, cephalosporin, gibberellin, lo
vastatin

6.  Some fungi accumulate primary metabolites
 Citric acid
 Fumaric acid
 Ethanol
 Lactic acid

7.  What are the reasons for interest in secondary
metabolites?
 industries:
i. Antibiotic: Penicillin and cephalosporin
ii. Itaconic acid: textile industries
iii. Gibberellin: plant growth regulator
iv. Animal feed
 Pigment
 Bioluminiscences

8.  Mycotoxin
 Aflatoxin: attack crops and cereals, by Fusarium.
 Zearalenone: attack animals (poultry and swine)- cause
infertility and abortion. Can be absorbed by human
skin.
 Phytotoxin and plant growth regulators produced by
pathogenic fungi
 HC toxin: attack Zeamays (maize), from Cochliobolus
carbonum, it is a host specific toxin
 Amatoxin: by Amanita phalloides- A subgroup toxin
 Gibberellin and cytokinins: plant growth regulators

9.  Classified based on 5 main metabolic sources:
1. Amino acid
2. Shikimic acid pathway for biosynthesis of aromatic
amino acid
3. Polyketide biosynthetic pathway from Acetyl CoA
4. Mevalonic pathway from Acetyl CoA
5. Polysaccharides and peptidopolysaccharides
*3 and 4- most involved in production of secondary
metabolites
*amino acid- biosynthetic origins in gycolysis and TCA cycle

10.  Many Ascomycetes and several bacteria
(e.g., Streptomyces) make the β-lactam
antibiotic, Penicillin and Cephalosporin.
 Penicillium chrysogenum, Aspergillus
nidulans, Acremonium chrysogenum
 The precursor substrates for biosynthesis β-lactam are
amino acids
- Show the clear interaction of secondary
with primary metabolites.

11.  Penicillins and cephalopsorins share the initial steps of
their biosynthesis, beginning with Val, Cys and α-
aminoadipic acid.
 These amino acids have their origins in the TCA
 Naturally occurring penicillins produced in the absences of
the side chain precursor supplement in the medium all
contain fatty acid side chains
 Peniciilin F, Penicillin K –derivatives of penicillin with
different side chains

12.  The evolutionary origin of secondary metabolic
pathway comes from sequence comparisons of the
cloned genes
 The genes cloned from Penicillin
chrysogenum, Aspergillus nidulans, Acremonium
chrysogenum
 Revealed in comparison with the analogous genes from
the prokaryotes Streptomyces lipmanii and S.
clavuligerus, striking similarity in both the nucleic
acid and amino acid sequences.

13.  Common evolutionary origin and cross kingdom
transfer of the genes may have occurred about 370 mil
years ago
 P. chrysogenum produces 17 secondary metabolites
 PATULIN- polyketide-related antibiotic produced by
P. Urticae also known as P. Patulum and P.
griseofulvum
 Biosynthesised by acetate malonate pathway

14.  Aspergillus flavus and A. parasiticus
 Carcinogenic properties
 Belong to the polyketide family of secondary
metabolites derived from Acetyl CoA
Aspergillus flavus- stained by
lactophenol blue