Heterologous production of bioactive xenoacremone analogs in Aspergillus nidulans / 中国天然药物

Tyrosine-decahydrofluorene derivatives are a class of hybrid compounds that integrate the properties of polyketides and nonribosomal peptides. These compounds feature a [6.5.6] tricarbocyclic core and a para-cyclophane ether moiety in their structures and exhibit anti-tumor and anti-microbial activities. In this study, we constructed the biosynthetic pathway of xenoacremones from Xenoacremonium sinensis ML-31 in the Aspergillus nidulans host, resulting in the identification of four novel tyrosine-decahydrofluorene analogs, xenoacremones I-L (1-4), along with two known analogs, xenoacremones A and B. Remarkably, compounds 3 and 4 contained a 12-membered para-cyclophane ring system, which is unprecedented among tyrosine-decahydrofluorene analogs in X. sinensis. The successful reconstruction of the biosynthetic pathway and the discovery of novel analogs demonstrate the utility of heterologous expression strategy for the generation of structurally diverse natural products with potential biological activities.

Relationship of pks gene islands with virulence genes and biofilm formation in Klebsiella pneumoniae / 中华微生物学和免疫学杂志

Objective:To investigate the relationship of pks gene islands with virulence genes, capsular serotypes and biofilm formation in Klebsiella pneumoniae ( Kp). Methods:A total of 113 Kp clinical isolates were collected in the First Affiliated Hospital of Fujian Medical University and divided into two groups based on the presence of pks gene islands: pks+ and pks- groups. The hypermucoviscous (HM) phenotype was detected by string test. Five virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and six common capsular serotypes (K1, K2, K5, K20, K54, K57) were detected by polymerase chain reaction (PCR). The biofilm formation ability was measured by crystal violet staining. Results:Among the 113 Kp isolates, 46 were pks+ strains and 67 were pks- strains. The detection rate of HM phenotype was higher in the pks+ group than in the pks- group [87.0% (40/46) vs 43.3% (29/67)]. The detection rates of virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and K1 serotype in the pks+ group were also higher than those in the pks- group ( P<0.05). The biofilm formation ability of the pks+ strains was higher than the pks- strains ( P<0.05). Conclusions:Kp strains carrying pks gene islands were likely to display a HM phenotype and mainly belonged to the K1 serotype. Most of the pks+Kp strains carried the virulence genes of peg-344, rmpA, rmpA2, iucA and iroB, and had a greater ability to form biofilms.

Overexpression of a fusion protein of 4-coumaroyl-CoA ligase and polyketide synthase for raspberry ketone production in Chlamydomonas reinhardtii / 生物工程学报

Raspberry ketones have important therapeutic properties such as anti-influenza and prevention of diabetes. In order to obtain raspberry ketone from Chlamydomonas reinhardtii, two enzymes catalyzing the last two steps of raspberry ketone synthesis, i.e. 4-coumaryl-CoA ligase (4CL) and polyketide synthase (PKS1), were fused using a glycine-serine-glycine (GSG) tripeptide linker to construct an expression vector pChla-4CL-PKS1. The fusion gene 4CL-PKS1 driven by a PSAD promoter was transformed into a wild-type (CC125) and a cell wall-deficient C. reinhardtii (CC425) by electroporation. The results showed the recombinant C. reinhardtii strain CC125 and CC425 with 4CL-PKS1 produced raspberry ketone at a level of 6.7 μg/g (fresh weight) and 5.9 μg/g (fresh weight), respectively, both were higher than that of the native raspberry ketone producing plants (2-4 μg/g).

Tricarbocyclic core formation of tyrosine-decahydrofluorenes implies a three-enzyme cascade with XenF-mediated sigmatropic rearrangement as a prerequisite

Tyrosine-decahydrofluorene derivatives feature a fused [6.5.6] tricarbocyclic core and a 13-membered

Analysis of bacterial diversity associated with polyketide synthase (PKS) gene in brackish metagenome of TsoKar Lake of Ladakh, India

Aim: To explore bacterial diversity associated to polyketide synthase (PKS) genes in the TsoKar brackish metagenome.Methodology: The metagenomic DNA of TsoKar water and sediment samples were isolated and amplified using pks specific degenerate primers. PCR amplified products were analysed using Ion Torrent PGM platform and revealed a total of 2,11,030 reads with 534 contigs and 55% of G+C content. The results of BLASTx was further analyzed for species diversity using MEGAN5 software. Results: Halomonas was found to be the dominant phyla followed by Cyanobium, Acinetobacter and Burkholderia, respectively, along with majority of uncultured microorganisms present in TsoKar metagenome. Since TsoKar is a brackish water lake, and brackish aquatic ecosystems are a major hub of diverse microbes was also revealed in this study. TsoKar metagenomic sequence with accession number SRR8381943 was deposited in SRA database. Interpretation: TsoKar Lake is considered as one of the most important biosphere reserves. The results of this study confirm that this unique niche harbors good bacterial diversity associated with polyketide synthase genes, which justifies the idea of bioprospecting such niches for the discovery of novel metabolites like antimicrobial compounds using next-generation sequencing approach

Aspergillus niger as the Source of Ochratoxin A of Contaminated Pyrus communis in Taif Market

Fruits are one of the most important agricultural products that supply the body with vitamins and essential minerals elements, but it is contaminated by fungi during the period of growth, harvesting and storage. A. niger is one of the species that grows on the fruit during the period of storage, and secretes mycotoxins especially ochratoxin A. This study was conducted with the purpose of isolating and identifying different strains of A. niger from 20 samples of pear collected from Taif markets and to determine the ability of these strains to produce OTA. It was observed that showed that out of 20 pear samples collected, 19 samples were detected to be contaminated with different strains of A. niger and the strains were able to produce OTA. From 27 isolates of A. niger which was used to test the ability of production OTA, 10 strains only produced OTA. The range of OTA in all strains were 0.18 to 9.5 ppb. Representative 27 strains of ochratoxigenic and non ochratoxigenic black Aspergilli isolated were subjected for detection of ochratoxin biosynthesis genes, by using two sets of primer for two genes involved in ochratoxin biosynthetic pathway. Bands of the fragments of PKS15C-MeT and PKS15KS genes visualized at 998 and 776 bp, respectively. Whereas, the presence of four tested genes is not sufficient marker for differentatin between aflatoxigenic and non aflatoxigenic isolates.

Diversity and communities of culturable endophytic fungi from different tree peonies (geoherbs and non-geoherbs), and their biosynthetic potential analysis

Abstract To know more about the potential roles of endophytic fungi in the formation mechanism of Daodi medicinal material, diversity and communities of culturable endophytic fungi in three types of tree peonies were investigated. Endophytic fungi of three types of tree peonies were isolated and identified. The diversity was analyzed. Bayesian trees constructed by MrBayes 3.2.6 after phylogenetic analysis of the ITS sequences. The endophytic fungi potential for synthesis of natural products was assessed by means of detecting NRPS and PKS gene sequences. In total, 364 endophytic fungi isolates representing 26 genera were recovered from Paeonia ostii 'Feng Dan', Paeonia ostii 'Luoyang Feng Dan', and Paeonia suffruticosa 'Luoyang Hong'. More culturable endophytic fungi appeared in P. suffruticosa 'Luoyang Hong' (206) compared with P. ostii 'Feng Dan' (60) and P. ostii 'Luoyang Feng Dan' (98). The fungal community of P. ostii 'Feng Dan' had the highest richness and diversity. PKSs and NRPS detection rates of endophytic fungi from P. ostii 'Feng Dan' are both the highest among the three types of tree peonies. Results indicate that endophytic fungus is an important factor of Daodi Cortex Moutan forming, and endophytic fungi in peony are related to genuineness of Cortex Moutan.

Diversity and communities of culturable endophytic fungi from different tree peonies (geoherbs and non-geoherbs), and their biosynthetic potential analysis

Abstract To know more about the potential roles of endophytic fungi in the formation mechanism of Daodi medicinal material, diversity and communities of culturable endophytic fungi in three types of tree peonies were investigated. Endophytic fungi of three types of tree peonies were isolated and identified. The diversity was analyzed. Bayesian trees constructed by MrBayes 3.2.6 after phylogenetic analysis of the ITS sequences. The endophytic fungi potential for synthesis of natural products was assessed by means of detecting NRPS and PKS gene sequences. In total, 364 endophytic fungi isolates representing 26 genera were recovered from Paeonia ostii Feng Dan, Paeonia ostii Luoyang Feng Dan, and Paeonia suffruticosa Luoyang Hong. More culturable endophytic fungi appeared in P. suffruticosa Luoyang Hong (206) compared with P. ostii Feng Dan (60) and P. ostii Luoyang Feng Dan (98). The fungal community of P. ostii Feng Dan had the highest richness and diversity. PKSs and NRPS detection rates of endophytic fungi from P. ostii Feng Dan are both the highest among the three types of tree peonies. Results indicate that endophytic fungus is an important factor of Daodi Cortex Moutan forming, and endophytic fungi in peony are related to genuineness of Cortex Moutan.

Prevalence of Escherichia coli Carrying pks Islands in Bacteremia Patients

Escherichia coli can harbor genomic pks islands that code for a polyketide-peptide genotoxin known as colibactin. E. coli strains carrying pks islands trigger genetic instability. pks islands have been significantly associated with bacteremia. We investigated the molecular epidemiology of bacteremic E. coli isolates and the prevalence of bacteremia-causing E. coli carrying pks islands. A total of 146 E. coli isolates were collected at a tertiary-care hospital from January 2015 to December 2016. The phylogenetic groups were determined by multiplex PCR. All isolates were screened by PCR for sequence type 131 (ST131)-associated single-nucleotide polymorphisms (SNPs) in mdh and gyrB. For detection of pks islands, we performed PCR for the clbB and clbN genes as colibactin system markers. Phylogenetic group B2 was the most common, accounting for 54.1% (N=79) of the isolates, followed by group D with 29.5% (N=43), group A with 11.6% (N=17), and group B1 with 4.8%. Of the group B2 isolates, 40.5% were ST131 strains and 32.9% carried pks islands. Only three ST131 isolates in group B2 carried the clbB and clbN genes, while the other 23 ST131 isolates did not. The pks gene might not be associated with ST131 strains.

The introduction of PKS-NRPS databases / 中国药学杂志

Polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) are two kinds of multi-modular enzymes, which biosynthesize highly complex polyketides and nonribosonmal peptides, respectively. Both of these two secondary metabolites are of considerable pharmaceutical relevance and are thought to cover diverse biological functions. With the development of sequencing and bioinformatics, data about PKS/NRPS are increasing rapidly. New PKS/NRPS databases are created to analyze gene sequence and predict the functions and structures of natural products. In this article, we introduce five newest databases including PKMiner, NRPSsp, NaPDoS, ClusterMine360, and IMG-ABC, with the goal to help researchers choose databases.

Inheritance in endophytic fungi from Melia toosendan and diversity of genes of PKS and NRPS / 中草药

Objective: To explore the inheritance in endophytic fungi from Melia toosendan and the diversity of the genes of PKS and NRPS and to lay the foundation of looking for the synthesis of the potential strains of bioactive substances. Methods: To identify the morphology of 39 strains of endophytic fungi separated from the medicinal plant M. toosendan; The ITS sequences and the genes of PKS and NRPS were obtained using PCR method, compared by BLAST and analyzed by phylogenesis after sequencing. Results: The morphological identification and phylogenetic analysis on 39 strains showed that all strains of endophytic fungi from M. toosendan belonged to 25 categories, mainly Penicillium, Aspergillus, and Trichoderma. The dominant fungus species were Aspergillus (17.9%), and Penicillium (15.4%). PKS (12) and NRPS (6) genes were detected in this study, All NRPS genes were Penicillium. Conclusion: The endophytic fungi of M. toosendan have a rich genetic diversity and strong potential of synthesis of bioactive substances. Further research on Penicillium and Aspergillus should be carried out.

Characterisation of pks15/1 in clinical isolates of Mycobacterium tuberculosis from Mexico

Tuberculosis (TB) is an infectocontagious respiratory disease caused by members of the Mycobacterium tuberculosis complex. A 7 base pair (bp) deletion in the locus polyketide synthase (pks)15/1 is described as polymorphic among members of the M. tuberculosis complex, enabling the identification of Euro-American, Indo-Oceanic and Asian lineages. The aim of this study was to characterise this locus in TB isolates from Mexico. One hundred twenty clinical isolates were recovered from the states of Veracruz and Estado de Mexico. We determined the nucleotide sequence of a ± 400 bp fragment of the locus pks15/1, while genotypic characterisation was performed by spoligotyping. One hundred and fifty isolates contained the 7 bp deletion, while five had the wild type locus. Lineages X (22%), LAM (18%) and T (17%) were the most frequent; only three (2%) of the isolates were identified as Beijing and two (1%) EAI-Manila. The wild type pks15/1 locus was observed in all Asian lineage isolates tested. Our results confirm the utility of locus pks15/1 as a molecular marker for identifying Asian lineages of the M. tuberculosis complex. This marker could be of great value in the epidemiological surveillance of TB, especially in countries like Mexico, where the prevalence of such lineages is unknown.

Apoptosis, production of MMP9, VEGF, TNF- and intracellular growth of M. tuberculosis for different genotypes and different pks15/1 genes.

Background: A previous study of IS6110 RFLP and spoligotyping of M. tuberculosis isolates from 152 Thai patients with tuberculous meningitis revealed a significantly higher percentage (57%) of the Beijing genotype as compared to isolates obtained from pulmonary tuberculosis. We postulated that the M. tuberculosis Beijing genotype is likely to be more virulent than others. Objectives: Ten M. tuberculosis cerebrospinal fluid (CSF) isolates from five RFLP groups, together with different characteristics of pks15/1, M. tuberculosis H37Rv and M. bovis BCG, were investigated for their virulence in vitro. Methods: In this study, THP-1 cells were used as host cells to determine the intracellular growth and the induction of MMP9, VEGF, TNF-α and apoptosis. Determinations of the cytokine production and apoptosis were based on available commercial kits using ELISA techniques. Results: No significant difference in intracellular multiplication was found between the M. tuberculosis CSF isolates. Three isolates, consisting of 2 Nonthaburi and 1 heterogeneous isolate, were found to stimulate high TNF-α and MMP-9 production during the early infection period.They were isolated from 3 different patients, 2 of whom died with initial stages II and III. This result suggested that there might be an association between TNF-α and MMP-9 production that could account for the specific virulent nature of Nonthaburi strains. VEGF production was determined and comparable levels were found in all isolates. No significant apoptosis was detected in M. tuberculosis CSF isolates. No significant differences suggesting that the 2 Beijing strains are more virulent than the others were observed. Conclusion: The predominance of the Beijing strains in cases of tuberculous meningitis (TBM) in Thai patients is not a result of their hypervirulence.

Computational Approach for the Analysis of Post-PKS Glycosylation Step

We introduce a computational approach for analysis of glycosylation in Post-PKS tailoring steps. It is a computational method to predict the deoxysugar biosynthesis unit pathway and the substrate specificity of glycosyltransferases involved in the glycosylation of polyketides. In this work, a directed and weighted graph is introduced to represent and predict the deoxysugar biosynthesis unit pathway. In addition, a homology based gene clustering method is used to predict the substrate specificity of glycosyltransferases. It is useful for the rational design of polyketide natural products, which leads to in silico drug discovery.

Computational Approach for Biosynthetic Engineering of Post-PKS Tailoring Enzymes

Compounds of polyketide origin possess a wealth of pharmacological effects, including antibacterial, antifungal, antiparasitic, anticancer and immunosuppressive activities. Many of these compounds and their semisynthetic derivatives are used today in the clinic. Most of the gene clusters encoding commercially important drugs have also been cloned and sequenced and their biosynthetic mechanisms studied in great detail. The area of biosynthetic engineering of the enzymes involved in polyketide biosynthesis has recently advanced and been transferred into the industrial arena. In this work, we introduce a computational system to provide the user with a wealth of information that can be utilized for biosynthetic engineering of enzymes involved in post-PKS tailoring steps. Post-PKS tailoring steps are necessary to add functional groups essential for the biological activity and are therefore important in polyketide biosynthesis.

Advances on Polyketide Biosynthesise by Microorganism and the Diversity of Polyketide Synthases / 微生物学通报

Polyketides are very large group of natural products with functional and structural diversity.Most of them are produced by microor- ganism and have medicinal activities,including antibiotic,anticancer,antifungal and antiparasitic properties.The researchs in this area have progressed greatly.More and more polyketides are discovered,on the other hand the mechanisms of biosynthesis of those various polyketides are researched more deeply and clearly.The article reviewed the progress of the research in the diversity of polyketide synthases and the mechanisms of polyketide biosynthesise.

PROGRESS IN MOLECULAR BIOLOGY OF NATAMYCIN / 微生物学通报

Natamycin is a polyene macrolide antifungal antibiotic ,which is wide ly used in the food industry in order to prevent mould contamination .Biosynthe s is gene cluster of natamycin is discovered by the overall of progress in molecul ar biology of natamycin, including 16 open reading frames which includes the gen e for 26-member ring formation of natamycin (pimS0-pimS4 ) and the modifying gene s, and the function of the protein including polyketide synthases(PKSs)、PimD、P imJ、PimK were studied