Strategies for Accessing Microbial Secondary Metabolites from Silent Biosynthetic Pathways

Cichewicz, Robert H.; Henrikson, Jon C.; Wang, Xiaoru; Branscum, Katie M.

doi:10.1128/9781555816827.ch7

Cited by 6 publications

(11 citation statements)

References 97 publications

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“…Fungal metabolites, especially those derived from marine fungi, are particularly important and have attracted considerable attention [ 5 , 6 , 7 ]. In spite of their roles in drug development, the majority of cultured microbes cannot be used for drug production because the pathways that produce secondary metabolites are silenced in standard culture conditions [ 8 , 9 , 10 , 11 , 12 ]. Various strategies have been developed to activate silenced pathways and elicit metabolite production from microbial isolates.…”

Section: Introductionmentioning

confidence: 99%

“…Various strategies have been developed to activate silenced pathways and elicit metabolite production from microbial isolates. Rational genetic engineering has provided promising new techniques that may reveal additional methods of metabolite production [ 8 , 9 , 10 , 11 , 12 ]. However, current strategies still suffer from significant technical challenges that limit their utility [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

“…Rational genetic engineering has provided promising new techniques that may reveal additional methods of metabolite production [ 8 , 9 , 10 , 11 , 12 ]. However, current strategies still suffer from significant technical challenges that limit their utility [ 9 ]. The complex gene manipulations used in those techniques have also restricted their use in natural products.…”

Section: Introductionmentioning

confidence: 99%

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A Practical Strategy to Discover New Antitumor Compounds by Activating Silent Metabolite Production in Fungi by Diethyl Sulphate Mutagenesis

Fang

Li³

et al. 2014

Marine Drugs

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Many fungal biosynthetic pathways are silent in standard culture conditions, and activation of the silent pathways may enable access to new metabolites with antitumor activities. The aim of the present study was to develop a practical strategy for microbial chemists to access silent metabolites in fungi. We demonstrated this strategy using a marine-derived fungus Penicillium purpurogenum G59 and a modified diethyl sulphate mutagenesis procedure. Using this strategy, we discovered four new antitumor compounds named penicimutanolone (1), penicimutanin A (2), penicimutanin B (3), and penicimutatin (4). Structures of the new compounds were elucidated by spectroscopic methods, especially extensive 2D NMR analysis. Antitumor activities were assayed by the MTT method using human cancer cell lines. Bioassays and HPLC-photodiode array detector (PDAD)-UV and HPLC-electron spray ionization (ESI)-MS analyses were used to estimate the activated secondary metabolite production. Compounds 2 and 3 had novel structures, and 1 was a new compound belonging to a class of very rare natural products from which only four members are so far known. Compounds 1–3 inhibited several human cancer cell lines with IC50 values lower than 20 μM, and 4 inhibited the cell lines to some extent. These results demonstrated the effectiveness of this strategy to discover new compounds by activating silent fungal metabolic pathways. These discoveries provide rationale for the increased use of chemical mutagenesis strategies in silent fungal metabolite studies.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Practical Strategy to Discover New Antitumor Compounds by Activating Silent Metabolite Production in Fungi by Diethyl Sulphate Mutagenesis

Fang

Li³

et al. 2014

Marine Drugs

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“…Although a great number of novel and bioactive compounds have been increasingly discovered from marine microbial sources [1,2,3,4,5,6,7,8,9,10,11], the great biosynthetic potential of microbial isolates, including the fungi, has so far not been fully elicited, because their major biosynthetic pathways that produce secondary metabolites are silent in laboratory culture conditions [12,13,14,15,16]. Various strategies have been developed to activate silent pathways to elicit the metabolic potentials of microbial isolates [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26].…”

Section: Introductionmentioning

confidence: 99%

Activation of Dormant Secondary Metabolite Production by Introducing Neomycin Resistance into the Deep-Sea Fungus, Aspergillus versicolor ZBY-3

Dong¹,

Cui²,

Li³

et al. 2014

Marine Drugs

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A new ultrasound-mediated approach has been developed to introduce neomycin-resistance to activate silent pathways for secondary metabolite production in a bio-inactive, deep-sea fungus, Aspergillus versicolor ZBY-3. Upon treatment of the ZBY-3 spores with a high concentration of neomycin by proper ultrasound irradiation, a total of 30 mutants were obtained by single colony isolation. The acquired resistance of the mutants to neomycin was confirmed by a resistance test. In contrast to the ZBY-3 strain, the EtOAc extracts of 22 of the 30 mutants inhibited the human cancer K562 cells, indicating that these mutants acquired a capability to produce antitumor metabolites. HPLC-photodiode array detector (PDAD)-UV and HPLC-electron spray ionization (ESI)-MS analyses of the EtOAc extracts of seven bioactive mutants and the ZBY-3 strain indicated that diverse secondary metabolites have been newly produced in the mutant extracts in contrast to the ZBY-3 extract. The followed isolation and characterization demonstrated that six metabolites, cyclo(d-Pro-d-Phe) (1), cyclo(d-Tyr-d-Pro) (2), phenethyl 5-oxo-l-prolinate (3), cyclo(l-Ile-l-Pro) (4), cyclo(l-Leu-l-Pro) (5) and 3β,5α,9α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (6), were newly produced by the mutant u2n2h3-3 compared to the parent ZBY-3 strain. Compound 3 was a new compound; 2 was isolated from a natural source for the first time, and all of these compounds were also not yet found in the metabolites of other A. versicolor strains. Compounds 1–6 inhibited the K562 cells, with inhibition rates of 54.6% (1), 72.9% (2), 23.5% (3), 29.6% (4), 30.9% (5) and 51.1% (6) at 100 μg/mL, and inhibited also other human cancer HL-60, BGC-823 and HeLa cells, to some extent. The present study demonstrated the effectiveness of the ultrasound-mediated approach to activate silent metabolite production in fungi by introducing acquired resistance to aminoglycosides and its potential for discovering new compounds from silent fungal metabolic pathways. This approach could be applied to elicit the metabolic potentials of other fungal isolates to discover new compounds from cryptic secondary metabolites.

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“…These “cryptic clusters” were sometimes found to be under some form of epigenetic control, so when small molecules that were demethylase or histone deacetylase (HDAC) inhibitors, were added to a single microbe fermentation, the “mixture” could produce molecules that had not previously been reported. A series of excellent papers demonstrating these techniques were published by the Cichewicz group at the University of Oklahoma in 2009–2010 and these should be consulted for this type of experimentation (Fisch et al, 2009; Henrikson et al, 2009; Cichewicz, 2010; Cichewicz et al, 2010). …”

Section: Mimicking In Situ Microbial Interactionsmentioning

confidence: 99%

Predominately Uncultured Microbes as Sources of Bioactive Agents

Newman¹

2016

Front. Microbiol.

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In this short review, I am discussing the relatively recent awareness of the role of symbionts in plant, marine-invertebrates and fungal areas. It is now quite obvious that in marine-invertebrates, a majority of compounds found are from either as yet unculturable or poorly culturable microbes, and techniques involving “state of the art” genomic analyses and subsequent computerized analyses are required to investigate these interactions. In the plant kingdom evidence is amassing that endophytes (mainly fungal in nature) are heavily involved in secondary metabolite production and that mimicking the microbial interactions of fermentable microbes leads to involvement of previously unrecognized gene clusters (cryptic clusters is one name used), that when activated, produce previously unknown bioactive molecules.

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Strategies for Accessing Microbial Secondary Metabolites from Silent Biosynthetic Pathways

Cited by 6 publications

References 97 publications

A Practical Strategy to Discover New Antitumor Compounds by Activating Silent Metabolite Production in Fungi by Diethyl Sulphate Mutagenesis

A Practical Strategy to Discover New Antitumor Compounds by Activating Silent Metabolite Production in Fungi by Diethyl Sulphate Mutagenesis

Activation of Dormant Secondary Metabolite Production by Introducing Neomycin Resistance into the Deep-Sea Fungus, Aspergillus versicolor ZBY-3

Predominately Uncultured Microbes as Sources of Bioactive Agents

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