Diversity and bioactivity of fungi associated with the marine sea cucumber Holothuria poli: disclosing the strains potential for biomedical applications

AIMS

Identification of the mycobiota associated to the marine echinoderm Holothuria poli and investigation of cytotoxic and pro-osteogenic potential of isolated strains.

METHODS AND RESULTS

Fungal strains were isolated from the animal's body-wall, intestine and faeces. The species identification was based on DNA barcoding and morphophysiological observations. Forty-seven species were identified, all are Ascomycota and mainly belonging to Aspergillus and Penicillium genera. Sixteen strains were grown on three media for chemical extraction. Cytotoxic activity was tested on a hepatic cancer cell line (HepG2), the cells viability was evaluated after treatment using a resazurin based assay (AlamarBlue). Pro-osteogenic activity was tested on human Mesenchymal stem cell, differentiation was measured as the alkaline phosphatase production through reaction with p-nitrophenylphosphate or as the cells ability to mineralize calcium using a colorimetric kit (StanBio). Cytotoxic activity was recorded for four fungal species while five of 48 extracts highlighted bioactivity towards human mesenchymal stem cells.

CONCLUSIONS

The presence of relevant animal-associated mycobiota was observed in H. poli and selected strains showed cytotoxic potential and pro-osteogenic activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our work represents the first report of a Mediterranean Sea cucumber mycobiota and highlights the isolates potential to synthetize compounds of pharmaceutical interest for regenerative medicine.

The culturable mycobiota associated with the Mediterranean sponges Aplysina cavernicola, Crambe crambe and Phorbas tenacior

Marine fungi are part of the huge and understudied biodiversity hosted in the sea. To broaden the knowledge on fungi inhabiting the Mediterranean Sea and their role in sponge holobiont, three sponges namely Aplysina cavernicola, Crambe crambe and Phorbas tenacior were collected in Villefranche sur Mer, (France) at about 25 m depth. The fungal communities associated with the sponges were isolated using different techniques to increase the numbers of fungi isolated. All fungi were identified to species level giving rise to 19, 13 and 3 species for P. tenacior, A. cavernicola and C. crambe, respectively. Of note, 35.7% and 50.0% of the species detected were either reported for the first time in the marine environment or in association with sponges. The mini-satellite analysis confirmed the uniqueness of the mycobiota of each sponge, leading to think that the sponge, with its metabolome, may shape the microbial community.

Identification of a Sorbicillinoid-Producing Aspergillus Strain with Antimicrobial Activity Against Staphylococcus aureus: a New Polyextremophilic Marine Fungus from Barents Sea

The exploration of poorly studied areas of Earth can highly increase the possibility to discover novel bioactive compounds. In this study, the cultivable fraction of fungi and bacteria from Barents Sea sediments has been studied to mine new bioactive molecules with antibacterial activity against a panel of human pathogens. We isolated diverse strains of psychrophilic and halophilic bacteria and fungi from a collection of nine samples from sea sediment. Following a full bioassay-guided approach, we isolated a new promising polyextremophilic marine fungus strain 8Na, identified as Aspergillus protuberus MUT 3638, possessing the potential to produce antimicrobial agents. This fungus, isolated from cold seawater, was able to grow in a wide range of salinity, pH and temperatures. The growth conditions were optimised and scaled to fermentation, and its produced extract was subjected to chemical analysis. The active component was identified as bisvertinolone, a member of sorbicillonoid family that was found to display significant activity against Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 30 μg/mL.

The culturable mycobiota of Flabellia petiolata: First survey of marine fungi associated to a Mediterranean green alga

Algae-inhabiting marine fungi represent a taxonomically and ecologically interesting group of microorganisms still largely neglected, especially in temperate regions. The aim of this study was to isolate and to identify the culturable mycobiota associated with Flabellia petiolata, a green alga frequently retrieved in the Mediterranean basin. Twenty algal thalli were collected from two different sampling sites in the Mediterranean Sea (Elba Island, Italy). A polyphasic approach showed the presence of a relevant alga-associated mycobiota with 64 taxa identified. The fungal isolates belonged mainly to Ascomycota (61 taxa), while only three Basidiomycota were detected. The phylogenetic position of sterile mycelia and cryptic taxa, inferred on the basis of LSU partial region, highlighted the presence of putative new phylogenetic lineages within Dothideomycetes and Sordariomycetes. This work represents the first quali-quantitative analysis of the culturable mycobiota associated to a green alga in the Mediterranean Sea.

The culturable mycobiota of a Mediterranean marine site after an oil spill: isolation, identification and potential application in bioremediation

Bioremediation of marine environment could be the response to oil spills threats. In the present study the fungal community from a Mediterranean marine site chronically interested by oil spills was investigated. Sixty-seven taxa were isolated from water sample and 17 from sediments; for many of the identified species is the first report in seawater and sediments, respectively. The growth of 25% of the fungal isolates was stimulated by crude oil as sole carbon source. Four strains were selected to screen hydrocarbons degradation using the 2,6-dichlorophenol indophenol (DCPIP) colorimetric assay. A. terreus MUT 271, T. harzianum MUT 290 and P. citreonigrum MUT 267 displayed a high decolorization percentage (DP≥68%). A. terreus displayed also the highest decreases of hydrocarbons compounds (up to 40%) quantified by gas-chromatography analysis. These results suggest that the selected fungi could represent potential bioremediation agents with strong crude oil degradative capabilities.

Marine fungi as source of new hydrophobins

Hydrophobins have been described as the most powerful surface-active proteins known. They are produced by filamentous fungi and exhibit a distinct amphiphilic structure determining their self-assembly at hydrophilic-hydrophobic interfaces and surfactant properties which have been demonstrated to be useful for several biotechnological applications. The marine environment represents a vast natural resource of new molecules produced by organisms growing in various stressful conditions. This study was focused on the screening of 100 marine fungi from Mycoteca Universitatis Taurinensis (MUT) for the identification of new hydrophobins. Four different methods were set up to extract hydrophobins of class I and II, from the mycelium or the culture broth of fungi. Six fungi were selected as the best producers of hydrophobins endowed with different characteristics. Their ability to form stable amphiphilic films and their emulsification capacity in the presence of olive oil was evaluated.

Dothideomycetes and Leotiomycetes sterile mycelia isolated from the Italian seagrass Posidonia oceanica based on rDNA data

Marine fungi represent a group of organisms extremely important from an ecological and biotechnological point of view, but often still neglected. In this work, an in-depth analysis on the systematic and the phylogenetic position of 21 sterile mycelia, isolated from Posidonia oceanica, was performed. The molecular (ITS and LSU sequences) analysis showed that several of them are putative new species belonging to three orders in the Ascomycota phylum: Pleosporales, Capnodiales and Helotiales. Phylogenetic analyses were performed using Bayesian Inference and Maximum Likelihood approaches. Seven sterile mycelia belong to the genera firstly reported from marine environments. The bioinformatic analysis allowed to identify five sterile mycelia at species level and nine at genus level. Some of the analyzed sterile mycelia could belong to new lineages of marine fungi.

Restriction fragment length polymorphism of the 5S-rRNA-NTS region: a rapid and precise method for plant identification

Molecular genetic methods have several advantages over classical morphological and chemical analyses. The genetic method requires genotype instead than phenotype, therefore PCR-based techniques have been widely used for a rapid identification of plant species, varieties and chemotypes. Recently, the molecular discrimination of some higher plant species has been evaluated using sequences of a 5S-rRNA gene spacer region. The variation in the nontranscribed sequence (NTS) region has been used in a number of plant species for studying intraspecific variation, genome evolution, and phylogenetic reconstruction. Here, we describe a rapid method based on the use of the 5S-rRNA-NTS region as a tool for plant DNA fingerprinting, which combines PCR, sequencing and restriction fragment length polymorphism analyses.

Chrysolina herbacea modulates terpenoid biosynthesis of Mentha aquatica L

Interactions between herbivorous insects and plants storing terpenoids are poorly understood. This study describes the ability of Chrysolina herbacea to use volatiles emitted by undamaged Mentha aquatica plants as attractants and the plant's response to herbivory, which involves the production of deterrent molecules. Emitted plant volatiles were analyzed by GC-MS. The insect's response to plant volatiles was tested by Y-tube olfactometer bioassays. Total RNA was extracted from control plants, mechanically damaged leaves, and leaves damaged by herbivores. The terpenoid quantitative gene expressions (qPCR) were then assayed. Upon herbivory, M. aquatica synthesizes and emits (+)-menthofuran, which acts as a deterrent to C. herbacea. Herbivory was found to up-regulate the expression of genes involved in terpenoid biosynthesis. The increased emission of (+)-menthofuran was correlated with the upregulation of (+)-menthofuran synthase.

Comparative characterization of Santolina insularis chemotypes by essential oil composition, 5S-rRNA-NTS sequencing and EcoRV RFLP-PCR

Santolina insularis (Genn ex Fiori) Arrig. is a medicinal plant whose essential oil shows antiviral and antibacterial activities and potent and selective cytotoxic activity against the human colon carcinoma cell line. The occurrence of several chemotypes makes the taxonomic identification of S. insularis hard to achieve. GC-MS essential oil analyses of four chemotypes (SI1, SI2, SI3 and SI4) revealed the presence of different percentages of santolina triene, beta-pinene, myrcene, beta-phellandrene, artemisia ketone and cis-chrysanthemol, allowing a chemical discrimination. Single fragments of the 5S-rRNA-NTS region of approximately 150, 170, 260 and 280bp were produced by SI1, SI2, SI3 and SI4, respectively, and the sequence alignment of the 5S-rRNA spacer region flanked by the 3'-and 5'-ends of the coding region confirmed a consistent difference between chemotypes. Furthermore, a PCR-RFLP method was applied. From the identified sequences, an EcoRV site could be found in chemotypes SI1, SI2 and SI3 in the 5S-rRNA spacer regions at 81 bp position; however, this site was absent in the chemotype SI4. This study, by showing remarkable chemical variation in the terpenoid profile and consistent genomic difference in the 5S-rRNA spacer regions, identified four chemotypes of S. insularis which could be grouped into two ecotypes, based on chemical and genomic analyses. The identification of specific gene sequences of the 5S-rRNA-NTS region and of a EcoRV site identified in this work can be used for a rapid and precise identification of the plant chemo-/ecotypes, complementing the essential oil chemical analysis.

Chemical and biomolecular characterization of Artemisia umbelliformis Lam., an important ingredient of the alpine liqueur "Genepi"

Artemisia umbelliformis Lam., an important alpine plant used for the preparation of flavored beverages, showed a remarkable intraspecific variability, at both genomic and gene product (secondary metabolites) levels. The variability of A. umbelliformis Lam. currently cultivated in Piedmont (Italy, Au1) and in Switzerland (Au2) was investigated by combining the chemical analysis of essential oil and sesquiterpene lactones and the molecular characterization of the 5S-rRNA-NTS gene by PCR and PCR-RFLP. Marked differences were observed between the two plants. Au1 essential oil contained alpha- and beta-thujones as the main components, whereas Au2 contained 1,8-cineole, borneol, and beta-pinene. Au1 sesquiterpene lactone fractions contained cis-8-eudesmanolide derivatives and Au2 the trans-6-germacranolide costunolide. Specific A. umbelliformis Au1 and Au2 primers were designed on the sequence of the 5S-rRNA gene spacer region. Furthermore, a PCR-restriction fragment length polymorphism (PCR-RFLP) method was applied using RsaI and TaqI restriction enzymes. Chemical and biomolecular data contributed to the characterization of A. umbeliformis chemotypes.

A Polar Cannabinoid from Cannabis Sativa Var. Carma

The aerial parts of Cannabis sativa var. Carma afforded a novel polar cannabinoid whose structure was established as rac-6′,7′-dihydro,6′,7′-dihydroxycannabigerol (carmagerol, 1) on the basis of spectroscopic data and semisynthesis from cannabigerol (2a). The dihydroxylation of the ω-double bond was detrimental to the anti-bacterial activity.