α-Pyrone derivatives with cyto-protective activity from two Takla Makan desert soil derived actinomycete Nocardiopsis strains recovered in seawater based medium

α-Pyrone mediates quorum sensing through the conservon system in Nocardiopsis sp

Actinobacteria produce a plethora of bioactive secondary metabolites that are often regulated by quorum-sensing signaling molecules via specific binding to their cognate TetR-type receptors. Here, we identified monocyclic α-pyrone as a new class of actinobacterial signaling molecules influencing quorum sensing process in Nocardiopsis sp. LDBS0036, primarily evidenced by a significant reduction in the production of phenazines in the pyrone-null mutant compared to the wild-type strain. Exogenous addition of the α-pyrone can partially restore the expression of some pathways to the wild strain level. Moreover, a unique multicomponent system referred to as a conservon, which is widespread in actinobacteria and generally contains four or five functionally conserved proteins, may play an important role in detecting and transmitting α-pyrone signals in LDBS0036. We found the biosynthetic gene clusters of α-pyrone and their associated conservon genes are highly conserved in Nocardiopsis, indicating the widespread prevalence and significant function of this regulate mechanism within Nocardiopsis genus. Furthermore, homologous α-pyrones from different actinobacterial species were also found to mediate interspecies communication. Our results thus provide insights into a novel quorum-sensing signaling system and imply that various modes of bacterial communication remain undiscovered.

Metabolic profiling and biological potential of the marine sponge associated Nocardiopsis sp. UR67 along with docking studies

This work was performed to dig into the phytochemical composition and bioactivities of Nocardiopsis sp. UR67 associated with the marine sponge Callyspongia sp. It was fermented in suspension and immobilised in calcium alginate bead cultures. The ethyl acetate extracts, afforded from the broth in each case named EG-49 and J-48g, respectively, revealed 16 chemical principles mostly belonging to polyketides, macrolides, and peptides. EG-49 and J-48g displayed anti-Candida albicans activity with IC50 values of 8.1 and 8.3 µg/mL, and a substantial cytotoxic effect against lung adenocarcinoma H1650 at IC50 12.6 and 13.7 µg/mL, respectively. However, only EG-49 exhibited a noteworthy anti-trypanosomal activity at 7.5 µg/mL. Molecular docking of the characterised compounds against Trypanosoma brucei trypanothione reductase demonstrated the highest binding models of griseochelin-methyl ester (9) and filipin-II (11), which drew considerable significance of the metabolites derived from Nocardiopsis sp. UR67 developing potential T. brucei trypanothione reductase inhibitors.

Microbial Dimerization and Chlorination of Isoflavones by a Takla Makan Desert-Derived Streptomyces sp. HDN154127

Sixteen new biisoflavones, bisoflavolins A-N (1-16), were discovered from cultures of the Takla Makan desert-derived strain Streptomyces sp. HDN154127. The chemical structures, including axial chirality, were elucidated by NMR, MS, and ECD analyses. Antibacterial activity of dimerized compounds was tested against seven different bacteria. The dimerized compounds showed better activity (MIC from 0.8 to 50.0 μM) than the corresponding monomers (daidzein and genistein, MIC > 50.0 μM). The rare dimeric and chlorinated structures in 1-16 were proved to be biotransformation products obtained from soy isoflavones and sodium chloride, which constituted the culture medium. This is the first report of an actinomycete that promotes both dimerization and chlorination utilizing natural isoflavones as skeletons sources.

iChip-Inspired Isolation, Bioactivities and Dereplication of Actinomycetota from Portuguese Beach Sediments

Oceans hold a stunning number of unique microorganisms, which remain unstudied by culture-dependent methods due to failures in establishing the right conditions for these organisms to grow. In this work, an isolation effort inspired by the iChip was performed using marine sediments from Memoria beach, Portugal. The isolates obtained were identified by 16S rRNA gene analysis, fingerprinted using BOX-PCR and ERIC-PCR, searched for the putative presence of secondary metabolism genes associated with polyketide synthase I (PKS-I) and non-ribosomal peptide synthetases (NRPS), screened for antimicrobial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, and had bioactive extracts dereplicated by LC/HRMS. Of the 158 isolated strains, 96 were affiliated with the phylum Actinomycetota, PKS-I and NRPS genes were detected in 53 actinomycetotal strains, and 11 proved to be bioactive (10 against E. coli, 1 against S. aureus and 1 against both pathogens). Further bioactivities were explored using an "one strain many compounds" approach, with six strains showing continued bioactivity and one showing a novel one. Extract dereplication showed the presence of several known bioactive molecules and potential novel ones in the bioactive extracts. These results indicate the use of the bacteria isolated here as sources of new bioactive natural products.

Genus Nocardiopsis: A Prolific Producer of Natural Products

Actinomycetes are currently one of the major sources of bioactive secondary metabolites used for medicine development. Accumulating evidence has shown that Nocardiopsis, a key class of actinomycetes, has the ability to produce novel bioactive natural products. This review covers the sources, distribution, bioactivities, biosynthesis, and structural characteristics of compounds isolated from Nocardiopsis in the period between March 2018 and 2021. Our results reveal that 67% of Nocardiopsis-derived natural products are reported for the first time, and 73% of them are isolated from marine Nocardiopsis. The chemical structures of the Nocardiopsis-derived compounds have diverse skeletons, concentrating on the categories of polyketides, peptides, terphenyls, and alkaloids. Almost 50% of the natural products isolated from Nocardiopsis have been discovered to display various bioactivities. These results fully demonstrate the great potential of the genus Nocardiopsis to produce novel bioactive secondary metabolites that may serve as a structural foundation for the development of novel drugs.

Characterization of Actinomycetes Strains Isolated from the Intestinal Tract and Feces of the Larvae of the Longhorn Beetle Cerambyx welensii

Actinomycetes constitute a large group of Gram-positive bacteria present in different habitats. One of these habitats involves the association of these bacteria with insects. In this work, we have studied twenty-four actinomycetes strains isolated from the intestinal tract and feces from larvae of the xylophagous coleopteran Cerambyx welensii and have shown that seventeen strains present hydrolytic activity of some of the following substrates: cellulose, hemicellulose, starch and proteins. Fourteen of the isolates produce antimicrobial molecules against the Gram-positive bacteria Micrococcus luteus. Analysis of seven strains led us to identify the production of a wide number of compounds including streptanoate, alpiniamide A, alteramides A and B, coproporphyrin III, deferoxamine, demethylenenocardamine, dihydropicromycin, nocardamine, picromycin, surugamides A, B, C, D and E, tirandamycins A and B, and valinomycin. A significant number of other compounds, whose molecular formulae are not included in the Dictionary of Natural Products (DNP), were also present in the extracts analyzed, which opens up the possibility of identifying new active antibiotics. Molecular identification of ten of the isolated bacteria determined that six of them belong to the genus Streptomyces, two of them are included in the genus Amycolatopsis and two in the genus Nocardiopsis.

A new diketopiperazine isolated from a Nocardiopsis strain TRM20105 guided by bioassay against Candida albicans

An actinomycete strain TRM20105 with antifungal activity was identified as Nocardiopsis dassonvillei subsp. dassonvillei DSM43111 (98.34% similarity) by 16S rDNA phylogenetic analysis and morphology observation. The fermentation broth of TRM20105 cultured with oat-soybean medium was subjected to discover bioactive compounds. Guided by antifungal bioassay against Candida albicans, a new diketopiperazine compound was purified via various column chromatographies together with pHPLC. The purified active compound was identified as 1-demethylnocazine A, (3Z,6Z)-5-methoxy-3,6-bis(4-methoxybenzylidene) -1,6-dihydropyrazin-2(3H)-one by the analyses of 1D & 2D NMR data.