Polyketide Synthase Type Research Articles

Diversity and Bioprospection of Gram-positive Bacteria Derived from a Mayan Sinkhole

Water-filled sinkholes known locally as cenotes, found on the Yucatán Peninsula, have remarkable biodiversity. The primary objective of this study was to explore the biotechnological potential of Gram-positive cultivable bacteria obtained from sediment samples collected at the coastal cenote Pol-Ac in Yucatán, Mexico. Specifically, the investigation aimed to assess production of hydrolytic enzymes and antimicrobial compounds. 16 S rRNA gene sequencing led to the identification of 49 Gram-positive bacterial isolates belonging to the phyla Bacillota (n = 29) and Actinomycetota (n = 20) divided into the common genera Bacillus and Streptomyces, as well as the genera Virgibacillus, Halobacillus, Metabacillus, Solibacillus, Neobacillus, Rossellomorea, Nocardiopsis and Corynebacterium. With growth at 55ºC, 21 of the 49 strains were classified as moderately thermotolerant. All strains were classified as halotolerant and 24 were dependent on marine water for growth. Screening for six extracellular hydrolytic enzymes revealed gelatinase, amylase, lipase, cellulase, protease and chitinase activities in 93.9%, 67.3%, 63.3%, 59.2%, 59.2% and 38.8%, of isolated strains, respectively. The genes for polyketide synthases type I, were detected in 24 of the strains. Of 18 strains that achieved > 25% inhibition of growth in the bacterial pathogen Staphylococcus aureus ATCC 6538, 4 also inhibited growth in Escherichia coli ATCC 35,218. Isolates Streptomyces sp. NCA_378 and Bacillus sp. NCA_374 demonstrated 50–75% growth inhibition against at least one of the two pathogens tested, along with significant enzymatic activity across all six extracellular enzymes. This is the first comprehensive report on the biotechnological potential of Gram-positive bacteria isolated from sediments in the cenotes of the Yucatán Peninsula.

Diverse biological activities and secondary metabolites profile of Penicillium brevicompactum HE19ct isolated from the high-Andean medicinal plant Perezia coerulescens

Endophytic fungi produced attractive primary and secondary metabolites for industries, pharmacology, and biotechnology. The bioactive potential of HE19ct, identified as Penicillium brevicompactum according to ITS-BenA-caM, was addressed. Antimicrobial and antioxidant activities and secondary metabolite contents using four culture media in Agar-plate (ApF) and Submerged (SmF) fermentation were evaluated. Some plant growth-promoting (PGP) traits and their related genes were tested. HE19ct exhibited antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, Candida albicans, C. tropicalis, Fusarium sp., Geotrichum candidum, and Alternaria sp. All cultures showed DPPH scavenging activity and phenolic compounds, where ethyl acetate extract of SmF with malt extract showed higher activity and SmF/ApF with potato-dextrose exhibited higher yield, respectively. HE19ct solubilized tricalcium-phosphate and produced siderophore, endoglucanase, proteinase, and amylase. It enhanced the alfalfa's germination at 15 °C, root development, and phenols production at 15 and 24 °C. Phenols, tannins, anthraquinones, triterpenoids/steroids, and alkaloids production were detected depending on culture media. Polyketide synthase type I gene (PksI), subtilisin-like protease prb 1 (Pbr), and siderophore D (sidD) were PCR-amplified. Finally, HE19CT could be a promising source of interesting bioactive compounds for pharmacology and agriculture mainly in extreme conditions, then metabolomic and functional genetic research must be performed to support their appropriate application.

Production of (hydroxy)benzoate-derived polyketides by engineered Pseudomonas with in situ extraction

Polyketides from (hydroxy)benzoates are an interesting group of plant polyphenolic compounds, whose biotechnological production is so far underrepresented due to their challenging heterologous biosynthesis. Efficient heterologous production of 2,4,6-tri- and 2,3′,4,6-tetrahydroxybenzophenone, 3,5-dihydroxybiphenyl, and 4-hydroxycoumarin by whole-cell biocatalysis in combination with in situ product extraction with an organic solvent was demonstrated. Production was highly dependent on the used CoA ligase and polyketide synthase type III. Therefore, different combinations of polyketide synthases and benzoate-CoA ligases were evaluated for their biosynthesis performance in the solvent-tolerant Pseudomonas taiwanensis VLB120. A solvent screening yielded 2-undecanone as biocompatible, extraction-efficient solvent with good phase separation. In aqueous-organic two-phase cultivations, this solvent extraction circumvents product instability in the aqueous cultivation medium, and it increases yields by reducing inhibitory effects. Complete de novo synthesis from glucose of all (hydroxy)benzoate-derived polyketides was achieved in two-phase cultivations with metabolically engineered strains. Additionally, mutasynthesis was applied to obtain fluorinated benzophenone derivatives.

Biological characteristics and ability of Streptomyces rochei BT02 to inhibit the Ralstonia solanacearum causing bacterial wilt disease

In the agricultural field, actinomycetes are outstanding biological control agents to inhibit the growth of pathogenic microorganisms. Based on the manual of bacterial classification of the International Streptomyces Project (ISP) and the 16S-rRNA gene sequence, the actinomycete BT02 strain was named Streptomyces rochei BT02. This strain contains two polyketide synthase type I (pks-I) and polyketide synthase type II (pks-II) genes related to antibiotic synthesis. The result showed that the actinomycetes S. rochei BT02 grow well at 31οC, 1% salt, pH 7.0, and assimilate different carbon and nitrogen sources. The S. rochei BT02 showed antibacterial activity against three tested strains of Ralstonia solanacearum (Minimum inhibitory concentration =15 mg/ml). In greenhouse conditions, this strain reduced 43.5% the wilt disease index. That demonstrated that S. rochei BT02 could be a promising source for the production of bioproducts.

The Antibacterial and Antibiofilm Activities of the Endophytic Bacteria Associated with Archidendron pauciflorum against Multidrug-Resistant Strains.

Endophytes associated with medicinal plants are a potential source of valuable natural products. This study aimed to evaluate the antibacterial and antibiofilm activities of endophytic bacteria from Archidendron pauciflorum against multidrug-resistant (MDR) strains. A total of 24 endophytic bacteria were isolated from the leaf, root, and stem of A. pauciflorum. Seven isolates showed antibacterial activity with different spectra against four MDR strains. Extracts derived from four selected isolates (1mg/mL) also displayed antibacterial activity. Among four selected isolates, DJ4 and DJ9 isolates exhibited the strongest antibacterial activity against P. aeruginosa strain M18, as indicated by the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) (DJ4 and DJ9 MIC: 7.81µg/mL; DJ4 and DJ9 MBC: 31.25µg/mL). 2 × MIC of DJ4 and DJ9 extracts was found to be the most effective concentration to inhibit more than 52% of biofilm formation and eradicate more than 42% of established biofilm against all MDR strains. 16S rRNA-based identification revealed four selected isolates belong to the genus Bacillus. DJ9 isolate possessed nonribosomal peptide synthetase (NRPS) gene, and DJ4 isolate possessed NRPS and polyketide synthase type I (PKS I) gene. Both these genes are commonly responsible for secondary metabolites synthesis. Several antimicrobial compounds, including 1,4-dihydroxy-2-methyl-anthraquinone and paenilamicin A1, were detected in the bacterial extracts. This study highlights endophytic bacteria isolated from A. pauciflorum provide a great source of novel antibacterial compounds.

Whole-genome sequencing-based characterization of Streptomyces sp. 6(4): focus on natural product.

We have sequenced the whole genome of Streptomyces sp. 6(4) isolated from tomato roots that presents antifungal activity against phytopathogenic fungi, mainly Bipolaris sorokiniana. The genome has almost 7 Mb and 3368 hypothetical proteins that were analysed and characterized in Uniprot with the emphasis on biological compounds. Multilocus sequence typing (MLST) analyses were performed in an effort to characterize and identify this isolate, resulting in a new sequence type (ST), classified as ST64. Phenetic and phylogenetic trees were constructed to investigate Streptomyces sp. 6(4) evolution and sequence similarity, and the isolate is a strain closer to Streptomyces prasinus and Streptomyces viridosporus . It is known that the genus Streptomyces possess huge metabolic capacity with the presence of cryptic genes. These genes are usually present in clusters, which are responsible for the production of diverse natural products, mainly antibiotics. In addition, 6(4) showed 11 biosynthetic gene clusters through antiSMASH, including 3 polyketide synthase (PKS) and non-ribosomal peptide synthase (NRPS) type clusters.

Phylogenetic Characterization and Detection of Polyketide Synthase Type I and Non-ribosomal Peptide Synthases Genes in Micromonospora Strains Isolated from Chilean Marine Sediments

There has been an increasing emphasis on the need to exploit un- and underexplored environments especially the marine environments for microbial and chemical diversity. Previous in-depth exploration of Chilean marine sediments have led to the isolation of members of the Micromonosporaceae, which require de-replication and characterization to establish taxonomic status along with screening of the isolates for the ability to produce bioactive compounds. This study was, therefore, embarked on with the aim of assessing phylogenetic relationship of the isolates and screening for novel polyketide synthases type I (PKS-I), non-ribosomal peptide synthases (NRPS) biosynthetic genes (BGC). This involved culture, de-replication by the traditional colour grouping to select representative strains, amplification of 16S rRNA, PKS-I and NRPS genes, sequencing and phylogenetic analysis. Thirty-four representative strains were selected from 66 Micromonospora species. Following the 16S rRNA gene sequence analysis, 11 belonged to the genus Micromonospora, 7 strains residing in the genera Exiguobacterium and Bacillus. The phylogenetic analysis of the 16S rRNA gene sequences of the strains inferred that these strains are novel members of this sub-order. The partial sequences of PKS-I and NRPS genes amplified from eight Micromonospora strains, produced matches with a variety of BGCs including Streptomyces noursei, S. neyagawaensis concanamycin A and Streptomyces sp. heptaene macrolide complex synthesis gene cluster. There exists an untapped microbial diversity in the Chilean marine sediments with great potential of been exploited for novel bioactive compounds as the search for newer and more potent natural products deepens.

Marine actinomycetes from Malaysia marine environments with antagonistic potential

Marine actinomycetes have garnered the attention of researchers worldwide due to their ability to produce unique and novel bioactive compounds. This study aimed at assessing the diversity and antagonistic potential of marine actinomycetes isolated from Langkawi Island, Kedah and Tioman Island, Johor. In a total of 215 isolates were successfully recovered of which 52% were obtained from Starch–yeast Extract Agar (SYE), 31.4% from Marine Agar (MA) and 16.3% from Actinomycetes Isolation Agar. Fourteen isolates were found to be positive of Polyketide Synthase Type I (PKS-I) and/or Non-ribosomal Peptide Synthetases (NRPS) genes and these isolates were then subjected to antimicrobial evaluation test against 3 Gram-positive bacteria – Staphylococcus aureus, Methicillinresistant S. aureus, Bacillus subtilis; 4 Gram-negative bacteria – Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Serratia marcescens; and 2 fungi – Candida albicans, Candida parapsilosis. Most isolates were able to inhibit at least one test microorganism. There is, however, no direct correlation between the presence of the biosynthetic genes and antagonistic potential as demonstrated by the lack of antimicrobial activity though PKS-I and/or NRPS genes were present. Molecular identification using the 16S rRNA gene revealed 10 isolates belonging to the genus Streptomyces and each representative of the genera Actinomadura, Rhodococcus, Gordonia and Salinispora. Among the isolates, Streptomyces sp. T55 is a potent antibacterial actinomycete while Streptomyces sp. T109 is a good antifungal agent. Further characterization of marine actinomycetes was conducted using scanning electron microscopy, culture characteristics on several media (SYE, MA, Potato Dextrose Agar, ISP2, ISP3, ISP4, Czapek Agar), NaCl tolerance and carbon sources utilization profile using BIOLOG. Findings from this study demonstrate the potential of Malaysia’s marine environment as a new resource of actinomycetes with biosynthetic capabilities which can be further explored for the development of the natural product.

Biocontrol potential of Streptomyces sp. CACIS-1.5CA against phytopathogenic fungi causing postharvest fruit diseases

BackgroundFungi are one of the microorganisms that cause most damage to fruits worldwide, affecting their quality and consumption. Chemical controls with pesticides are used to diminish postharvest losses of fruits. However, biological control with microorganisms or natural compounds is an increasing alternative to protect fruits and vegetables. In this study, the antifungal effect of Streptomyces sp. CACIS-1.5CA on phytopathogenic fungi that cause postharvest tropical fruit rot was investigated.Main bodyAntagonistic activity was evaluated in vitro by the dual confrontation over fungal isolates obtained from grape, mango, tomato, habanero pepper, papaya, sweet orange, and banana. The results showed that antagonistic activity of the isolate CACIS-1.5CA was similar to the commercial strain Streptomyces lydicus WYEC 108 against the pathogenic fungi Colletotrichum sp., Alternaria sp., Aspergillus sp., Botrytis sp., Rhizoctonia sp., and Rhizopus sp. with percentages ranging from 30 to 63%. The bioactive extract obtained from CACIS-1.5 showed a strong inhibition of fungal spore germination, with percentages ranging from 92 to 100%. Morphological effects as irregular membrane border, deformation, shrinkage, and collapsed conidia were observed on the conidia. Molecularly, the biosynthetic clusters of genes for the polyketide synthase (PKS) type I, PKS type II, and NRPS were detected in the genome of Streptomyces sp. CACIS-1.5CA.ConclusionsThis study presented a novel Streptomyces strain as a natural alternative to the use of synthetic fungicides or other commercial products having antagonistic microorganisms that were used in the postharvest control of phytopathogenic fungi affecting fruits.

P0116DISCOVERY OF A NOVEL ANTIMICROBIAL COMPOUND AGAINST PSEUDOMONAS AERUGINOSA FROM URINE OF KTX PATIENTS

Abstract Background and Aims The urinary microbiome harbors a great repertoire of bacteria, which possess an immense potential for the biosynthesis of different biochemical products such as polyketide synthases. Traditionally such compounds have been utilized as pharmaceutical drugs, for example as antibiotics or cytostatic substances or agrochemical agents. While examining the urinary microbiome of KTX-patients during AKI and concomitant antibiotic treatment a remarkable decrease of Candidatus solibacter usitatus in one patient attracted our attention. Surprised about detecting a putative close relative of a bacterium, which originally has been found in Australian soil in our patient’s urine, we examined the genome and protein coding regions of Candidatus solibacter usitatus. Thereby we identified a biosynthetic pathway, which allowed us to clone and produce an up-to-now unknown polyketide type 1 synthase, which we named Dananase. Method The dananase gene was synthesized, cloned into the pEX-A258 for replication and inserted into the p-TOPO-entry-D gateway vector following PCR amplification. The resultant insert was shifted into the pEXP1- DEST gateway vector. E. coli transformants were selected for dananase expression. BAP1-E. coli was transformed with the dananase-pEXP1- DEST expression plasmid and grown in liquid culture under induction with IPTG. The supernatant was filtered and utilized for antimicrobial activity testing against Pseudomonas aeruginosa. Metabolome analysis of BAP1- pEXP1-DEST-dananase following induction with IPDG was performed and compared to LB-media alone and supernatants of dummy plasmid transformed BAP1-E. coli. In addition, the molecular structure of dananase product was determined using trans-AT polyketide synthase predictor web application genome mining tool. Results The 1646 amino acid long polyketide synthase type 1 named dananase was cloned into pEXP1 expression vector and expressed in BAP1. The supernatant contained specific antimicrobial activity against clinical isolates of Pseudomonas aeruginosa. This highly active compound could be further purified by HPLC but not yet identified in its structure. In silico prediction analysis suggested a polyketide as follows CC(C(O)*)C=CC(CC(NC([K])C(CC(O)=O)=O)=O)=O. Mass spectrometric analysis revealed several Dananase-specific peaks representing most likely its product in the supernatant. Conclusion The dananase gene of Candidatus solibacter usitatus consists of 4941bp and encodes a polymodular polyketide synthase type-1, its product successfully inhibits growth of Pseudomonas aeruginosa in vitro.

In Silico Identification of Type III PKS Chalcone and Stilbene Synthase Homologs in Marine Photosynthetic Organisms.

Marine microalgae are photosynthetic microorganisms at the base of the marine food webs. They are characterized by huge taxonomic and metabolic diversity and several species have been shown to have bioactivities useful for the treatment of human pathologies. However, the compounds and the metabolic pathways responsible for bioactive compound synthesis are often still unknown. In this study, we aimed at analysing the microalgal transcriptomes available in the Marine Microbial Eukaryotic Transcriptome Sequencing Project (MMETSP) database for an in silico search of polyketide synthase type III homologs and, in particular, chalcone synthase (CHS) and stilbene synthase (STS), which are often referred to as the CHS/STS family. These enzymes were selected because they are known to produce compounds with biological properties useful for human health, such as cancer chemopreventive, anti-inflammatory, antioxidant, anti-angiogenic, anti-viral and anti-diabetic. In addition, we also searched for 4-Coumarate: CoA ligase, an upstream enzyme in the synthesis of chalcones and stilbenes. This study reports for the first time the occurrence of these enzymes in specific microalgal taxa, confirming the importance for microalgae of these pathways and giving new insights into microalgal physiology and possible biotechnological applications for the production of bioactive compounds.

Evaluation of Antagonistic and Plant Growth Promoting Potential of Streptomycessp. TT3 Isolated from Tea(Camellia sinensis) Rhizosphere Soil.

The present study investigated the antagonistic and plant growth promoting (PGP) potential of actinobacteria TT3 isolated from tea rhizosphere soil of Tocklai tea germplasm preservation plot, Jorhat, Assam, India. It is a Gram-positive, filamentous with flexible spore chains actinobacteria. The 16S rRNA gene sequencing and phylogenetic analysis indicated that TT3 is closely related to genus Streptomyces for which it was referred to as Streptomyces sp. TT3. It showed very promising PGP traits such as phosphate solubilization, production of indole acetic acid (IAA), siderophore, and ammonia. Evaluation of ethyl acetate extract of TT3 exhibited broad spectrum antagonistic activity against various fungal pathogens. This antagonistic Streptomyces sp. TT3 showed positive for polyketide synthase type II (PKS-II) gene, which was predicted to be involved in the production of actinorhodin as a secondary metabolite pathway product using DoBISCUIT database. Further, the crude ethyl acetate extract of TT3 was analyzed by using GC-MS and revealed the presence of significant chemical constituents responsible for antimicrobial activity. Thus, the present study suggests that actinobacteria isolated from the rhizosphere soil may be explored for the production of bioactive compounds and use as a potential candidate for tea and other agricultural application.

Isolation of endophytic fungi from South African plants, and screening for their antimicrobial and extracellular enzymatic activities and presence of type I polyketide synthases

Endophytes are bacteria or fungi which live inside the host plant and participate in many biological processes without causing disease or other adverse effects. Endophytes are recognised as a rich source of secondary metabolites with potentially useful pharmacological properties. Many South African medicinal plants are highly under-investigated sources of potentially useful endophytic microbes. In this report six endophytic fungi were obtained from the leaves, stems and roots of South African medicinal plants which are known for their traditional uses and pharmacological properties. The endophytic fungi were isolated from Cotyledon orbiculata L., Psychotria zombamontana (Kuntze) Petit, Tecomaria capensis (Thunb.) Lindl., Catha edulis (Vahl) Endl. and Melianthus comosus Vahl. The crude extracts of the isolated endophytic fungi were investigated for their antimicrobial potential, extracellular enzymatic activity and phosphate solubilization. Additionally, the present study used genetic screening to assess the ability of the endophytic fungi to synthesize bioactive compounds, indicated by the presence of the polyketide synthase type 1 (PKS 1) gene. In preliminary microbial inhibition screening the fungal extracts had promising antifungal activity against Cryptococcus neoformans and Candida albicans. Furthermore, the endophytic fungus Talaromyces funiculosus displayed extracellular enzymatic activity, namely xylanase and cellulase. Five fungal strains demonstrated ability to solubilize phosphate and three strains demonstrated the presence of polyketide synthase type 1 (PKS 1) gene. It is worth considering further investigation of their bioactive secondary metabolites.

Antimicrobial biosynthetic potential and diversity of culturable soil actinobacteria from forest ecosystems of Northeast India

Actinobacteria is a goldmine for the discovery of abundant secondary metabolites with diverse biological activities. This study explores antimicrobial biosynthetic potential and diversity of actinobacteria from Pobitora Wildlife Sanctuary and Kaziranga National Park of Assam, India, lying in the Indo-Burma mega-biodiversity hotspot. A total of 107 actinobacteria were isolated, of which 77 exhibited significant antagonistic activity. 24 isolates tested positive for at least one of the polyketide synthase type I, polyketide synthase type II or non-ribosomal peptide synthase genes within their genome. Their secondary metabolite pathway products were predicted to be involved in the production of ansamycin, benzoisochromanequinone, streptogramin using DoBISCUIT database. Molecular identification indicated that these actinobacteria predominantly belonged to genus Streptomyces, followed by Nocardia and Kribbella. 4 strains, viz. Streptomyces sp. PB-79 (GenBank accession no. KU901725; 1313 bp), Streptomyces sp. Kz-28 (GenBank accession no. KY000534; 1378 bp), Streptomyces sp. Kz-32 (GenBank accession no. KY000536; 1377 bp) and Streptomyces sp. Kz-67 (GenBank accession no. KY000540; 1383 bp) showed ~89.5% similarity to the nearest type strain in EzTaxon database and may be considered novel. Streptomyces sp. Kz-24 (GenBank accession no. KY000533; 1367 bp) showed only 96.2% sequence similarity to S. malaysiensis and exhibited minimum inhibitory concentration of 0.024 µg/mL against methicilin resistant Staphylococcus aureus ATCC 43300 and Candida albicans MTCC 227. This study establishes that actinobacteria isolated from the poorly explored Indo-Burma mega-biodiversity hotspot may be an extremely rich reservoir for production of biologically active compounds for human welfare.

Identification of polyketide synthase gene clusters in a phage P1-derived artificial chromosome library of a Philippine strain of Streptomyces sp. PCS3-D2

A phage P1-derived artificial chromosome (PAC) library was constructed from genomic DNA of Streptomyces sp. PCS3-D2. Polymerase chain reaction (PCR) screening of the PAC library revealed two clones, PAC16D and P222O, which were positively identified to harbor polyketide synthase (PKS) Type I and PKS Type III gene clusters, respectively. Restriction enzyme digestion showed that PAC16D and PAC222O contained a 130 kb and a 140 kb insert, respectively. Results of sequencing and bioinformatics analyses revealed that PAC16D comprised of a full-length PKS type I bafilomycin gene cluster while PAC222O harbored truncated siderophore and putative gene clusters as well as a complete PKS III biosynthetic gene cluster. The PKS III gene cluster had three genes similar to alkyl resorcinol biosynthetic genes, however majority of the novel gene cluster had little similarity to known PKS Type III gene clusters. The successful cloning and identification of these gene clusters from Streptomyces sp. PCS3-D2 serve as the jump off point to further genetic manipulation in order to produce the insecticidal natural product in a heterologous host.

Phylogenetic affiliation and antimicrobial effects of endophytic actinobacteria associated with medicinal plants: prevalence of polyketide synthase type II in antimicrobial strains.

The most diverse and versatile endophytic actinobacteria are relatively unexplored potential sources of bioactive metabolites useful for different medical, agricultural, and other commercial applications. Their diversity in symbiotic association with traditionally utilized medicinal plants of northeast India is scantly available. The present investigation assessed the genetic diversity of endophytic actinobacteria (n = 120) distributed around the root, stem, and leaf tissues of six selected medicinal plants (Emblica officinalis, Terminalia chebula, T. arjuna, Murraya koenigii, Rauwolfia serpentina, and Azadirachta indica) from three different protected areas of evergreen forest-the Gibbon Wildlife Sanctuary (GWS), the Kaziranga National Park (KNP), and the North East Ecological Park (NEEP) of Assam, India. The samples were collected in two seasons (summer and winter). The overall phylogenetic analysis showed significant genetic diversity with 18 distinct genera belonging to 12 families. Overall, the occurrence of Streptomyces genus was predominant across all three sampling sites (76.66%), in both the sampling season (summer and winter). Shannon's and Simpson's diversity estimates showed their presence at A. indica (1.496, 0.778), R. serpentina (1.470, 0.858), and E. officinalis (0.975, 0.353). Among the site sampled, GWS had the most diverse community of actinobacteria (Shannon = 0.86 and Simpson = 0.557). The isolates were antagonistically more active against the investigated plant pathogenic bacteria than fungal pathogens. Further analysis revealed the prevalence of polyketide synthase genes (PKS) type II (84%) and PKS type I (16%) in the genome of the antimicrobial isolates. The overall findings confirmed the presence of biosynthetically active diverse actinobacterial members in the selected medicinal plants which offer potential opportunities towards the exploration of biologically active compounds.

Classification and characterization of endophytic actinomycetes isolated from cinnamomum cassia presl

Currently, antibiotic resistance in pathogenic bacteria is a significant clinical problem with the increase of deseases and a serious public health concern. Thus, the identification of new antimicrobial agents, especially the secondary metabolites products by endophytic actinobacteria from medical plants could be promising sources of biologically active compounds in medical fields. This study focused on identification and evaluation of antimicrobial activity against pathogens; genes involved in their secondary metabolisms, and screening of anthracycline producing capacity (mainly presented in anti-cancer antibiotics) of YBQ75 isolated from Cinnamomum cassia Presl. plants in Yen Bai province. Based on manual of bacterial classification, method in International Streptomyces Project (ISP) and the 16S rRNA gene sequence (GenBank Acc. No. KR814822), the endophytic actinomycetes YBQ75 was named Streptomyces cavourensis YBQ75 with 100% identity. The strain S. cavourensis YBQ75 showed the remarkable antibacterial activities against 5 tested pathogens (Salmonella enterica ATCC 14028 (22.0 mm); Pseudomonas aeruginosa CNLM (19.3 mm); Staphylococcus epidermidis ATCC 12228 (19.3 mm); Enterobacter aerogenes ATCC 13048 (17.7 mm) and Proteus vulgaris CNLM (16.3 mm)) in the total of 9 tested pathogens. The detection of genes involved in antibiotic synthesis indicated that the strain S. cavourensis YBQ75 consists of all three genes related to antibiotic synthesis including polyketide synthase (pks-I) type I, polyketide synthase type II (pks-II) and nonribosomal peptide synthetase (nrps). Premarilly result showed that the strain S. cavourensis YBQ75 also present as an anthracycline productive actinomycetes. The resutls demonstrated that the endophytic actinomycetes S. cavourensis YBQ75 from medical plants could be promising sources for the production of antibiotics and anthracycline anticancer compounds.

Endophytic Paenibacillus amylolyticus KMCLE06 Extracted Dipicolinic Acid as Antibacterial Agent Derived via Dipicolinic Acid Synthetase Gene

Bioactive natural compounds play pivotal roles in drug discovery and the emergence of multi-drug resistance pathogens demands the development of better/new drugs. Paenibacillus amylolyticus KMCLE06 endophytic bacterium isolated from the medicinal plant Coix lachryma-jobi were analyzed for the potential bioactive secondary metabolite compounds and its gene responsible within polyketide synthases (PKS) clusters. Ethyl acetate extraction of P. amylolyticus KMCLE06 showed significant antibacterial activity which was further processed to partial purification and characterization for bioactive compound. The foremost bioactive component in extraction was found to be dipicolinic acid (DPA). The antibacterial activity showed remarkable activity compared to the commercial standard DPA against both gram-positive and gram-negative pathogens. The MIC and MBC concentrations for partially purified extracted DPA ranged from 62.5 to 125µg/ml and MBC from 208 to 250µg/ml, respectively. Sequence analysis of gene amplified using degenerative primer, amplified 543bp DNA region, revealing conserved putative open reading frame for dipicolinic acid synthetase (DpsA) key gene to produce DPA in most endospore forming bacteria. A search in the structural database for DpsA revealed significant homologous match with enoyl reductase one of the PKS type 1 module protein. This emphasizes endophytic P. amylolyticus KMCLE06 bacteria has presence of spoVF operon producing DPA via dipicolinic acid synthetase and lacks the polyketide synthase type 1 module cluster gene in its genome. And the bioactive compound DPA extracted acts as a stable remarkable antibacterial agent which can be potent compound for multi-resistance pathogens.

The potential impact of naturally produced antibiotics, environmental factors, and anthropogenic pressure on the occurrence of erm genes in urban soils

The occurrence of environmental antibiotic resistance genes (ARGs) are often attributed to selective pressure from antibiotics from point source pollution. However, the potential effects of natural production of antibiotics, environmental factors, and anthropogenic pressure on the development and spread of ARGs have not been fully investigated. This study evaluated the occurrence and distribution of erythromycin resistance methylase (erm) genes in urban soils. The ermA, ermB, ermC, ermD, ermF, ermG, ermT, and ermY genes were detected with detection frequencies ranging from 20% to 80% and abundances ranging between 5.95 × 101 and 6.94 × 106 copies g−1 dw soil. Both polyketide synthase (PKS) type I and type II biosynthesis genes—which are responsible for biosynthesis of polyketides, such as erythromycin—were detected in all soil samples with a range between 5.77 × 102 and 9.39 × 106 copies g−1 dw soil. The abundances of PKS genes were significantly correlated with 16S rRNA genes (r = 0.487 to 0.741, p < 0.001) and absolute abundances of ermB, ermC, ermD, ermG, and ermY (r = 0.302–0.490, p < 0.05), suggesting that the wide occurrence of ARGs in soils could be potentially driven by naturally produced antibiotics. Erythromycin was strongly correlated with ermB, ermC, ermF and ermY genes (r = 0.462 to 0.667, p < 0.05), but no significant correlation was observed between macrolides and PKS genes, suggesting other environmental factors may have contributed to detected macrolides. The fact that erm gene presented higher extent of variability than PKS genes in different land use types suggests that anthropogenic activity might also influence the occurrence of erm genes in urban soils.

Bioprospection of actinobacteria derived from freshwater sediments for their potential to produce antimicrobial compounds

BackgroundActinobacteria from freshwater habitats have been explored less than from other habitats in the search for compounds of pharmaceutical value. This study highlighted the abundance of actinobacteria from freshwater sediments of two rivers and one lake, and the isolates were studied for their ability to produce antimicrobial bioactive compounds.Results16S rRNA gene sequencing led to the identification of 84 actinobacterial isolates separated into a common genus (Streptomyces) and eight rare genera (Nocardiopsis, Saccharopolyspora, Rhodococcus, Prauserella, Amycolatopsis, Promicromonospora, Kocuria and Micrococcus). All strains that showed significant inhibition potentials were found against Gram-positive, Gram-negative and yeast pathogens. Further, three biosynthetic genes, polyketide synthases type II (PKS II), nonribosomal peptide synthetases (NRPS) and aminodeoxyisochorismate synthase (phzE), were detected in 38, 71 and 29% of the strains, respectively. Six isolates based on their antimicrobial potentials were selected for the detection and quantification of standard antibiotics using ultra performance liquid chromatography (UPLC–ESI–MS/MS) and volatile organic compounds (VOCs) using gas chromatography mass spectrometry (GC/MS). Four antibiotics (fluconazole, trimethoprim, ketoconazole and rifampicin) and 35 VOCs were quantified and determined from the methanolic crude extract of six selected Streptomyces strains.ConclusionInfectious diseases still remain one of the leading causes of death globally and bacterial infections caused millions of deaths annually. Culturable actinobacteria associated with freshwater lake and river sediments has the prospects for the production of bioactive secondary metabolites.