Cultivable epiphytic bacteria of the Chlorophyta Ulva sp.: diversity, antibacterial, and biofilm-modulating activities

AIMS

Macroalgae harbor a rich epiphytic microbiota that plays a crucial role in algal morphogenesis and defense mechanisms. This study aims to isolate epiphytic cultivable microbiota from Ulva sp. surfaces. Various culture media were employed to evaluate a wide range of cultivable microbiota. Our objective was to assess the antibacterial and biofilm-modulating activities of supernatants from isolated bacteria.

METHODS AND RESULTS

Sixty-nine bacterial isolates from Ulva sp. were identified based on 16S rRNA gene sequencing. Their antibacterial activity and biofilm modulation potential were screened against three target marine bacteria: 45%, mostly affiliated with Gammaproteobacteria and mainly grown on diluted R2A medium (R2Ad), showed strong antibacterial activity, while 18% had a significant impact on biofilm modulation. Molecular network analysis was carried out on four bioactive bacterial supernatants, revealing new molecules potentially responsible for their activities.

CONCLUSION

R2Ad offered the greatest diversity and proportion of active isolates. The molecular network approach holds promise for both identifying bacterial isolates based on their molecular production and characterizing antibacterial and biofilm-modulating activities.

The amnesic shellfish poisoning toxin, domoic acid: The tattoo of the king scallop Pecten maximus

Domoic acid (DA) is a potent neurotoxin produced by diatoms of the genus Pseudo-nitzschia and is responsible for Amnesic Shellfish Poisoning (ASP) in humans. Some fishery resources of high commercial value, such as the king scallop Pecten maximus, are frequently exposed to toxic Pseudo-nitzschia blooms and are capable of accumulating high amounts of DA, retaining it for months or even a few years. This poses a serious threat to public health and a continuous economical risk due to fishing closures of this resource in the affected areas. Recently, it was hypothesized that trapping of DA within autophagosomic-vesicles could be one reason explaining the long retention of the remaining toxin in P. maximus digestive gland. To test this idea, we follow the kinetics of the subcellular localization of DA in the digestive glands of P. maximus during (a) the contamination process - with sequential samplings of scallops reared in the field during 234 days and naturally exposed to blooms of DA-producing Pseudo-nitzschia australis, and (b) the decontamination process - where highly contaminated scallops were collected after a natural bloom of toxic P. australis and subjected to DA-depuration in the laboratory for 60 days. In the digestive gland, DA-depuration rate (0.001 day-1) was much slower than contamination kinetics. The subcellular analyses revealed a direct implication of early autophagy in DA sequestration throughout contamination (r = 0.8, P < 0.05), while the presence of DA-labeled residual bodies (late autophagy) appeared to be strongly and significantly related to slow DA-depuration (r = -0.5) resembling an analogous DA-tattooing in the digestive glands of P. maximus. This work provides new evidence about the potential physiological mechanisms involved in the long retention of DA in P. maximus and represents the baseline to explore procedures to accelerate decontamination in this species.

Revision of the genus Fascaplysinopsis, the type species Fascaplysinopsis reticulata (Hentschel, 1912) (Porifera, Dictyoceratida, Thorectidae) and descriptions of two new genera and seven new species

The present study examines the taxonomy of sponge specimens with unique chemistry collectively known as Fascaplysinopsis reticulata (Hentschel, 1912). Examination of Hentschels original species upon which the genus Fascaplysinopsis Bergquist, 1980 was based in conjunction with a comparison with recent Indo-west Pacific collections, using morphological and molecular analyses (ITS and 28S rDNA), revealed extensive variation. Fascaplysinopsis reticulata was found to be a species complex comprising the genus Fascaplysinopsis, as well as two new genera: Skolosachlys gen. nov. and Rubrafasciculus gen. nov. The new species of Fascaplysinopsis described are F. palauensis sp. nov., F. klobos sp. nov. and F. ronquinni sp. nov. The new species of Skolosachlys gen. nov. described herein are: S. enlutea sp. nov. and S. nidus sp. nov. The new species described of Rubrafasciculus gen. nov. includes: R. cerasus sp. nov. and R. fijiensis sp. nov..

Extracts from Wallis Sponges Inhibit Vibrio harveyi Biofilm Formation

Pathogenic bacteria and their biofilms are involved in many human and animal diseases and are a major public health problem with, among other things, the development of antibiotic resistance. These biofilms are known to induce chronic infections for which classical treatments using antibiotic therapy are often ineffective. Sponges are sessile filter-feeding marine organisms known for their dynamic symbiotic partnerships with diverse microorganisms and their production of numerous metabolites of interest. In this study, we investigated the antibiofilm efficacy of different extracts from sponges, isolated in Wallis, without biocidal activity. Out of the 47 tested extracts, from 28 different genera, 11 showed a strong activity against Vibrio harveyi biofilm formation. Moreover, one of these extracts also inhibited two quorum-sensing pathways of V. harveyi.

Isolation, Synthesis and Absolute Configuration of the Pericharaxins A and B, Epimeric Hydroxy-Polyene Glycerol Ethers from the Calcarean Sponge Pericharax heteroraphis

Naturally occurring epimeric hydroxy-polyene glycerol ether pericharaxins A (1a) and B (1b) were isolated from the calcarean sponge Pericharax heteroraphis. The structural and stereochemical characterization of both diastereoisomers were established on the basis of spectroscopic data analysis and total synthesis in seven steps. The mixture of pericharaxins A (1a) and B (1b) was proven to be epimeric by chiral-phase HPLC analysis of both synthetic and natural samples. Further separation of the epimers and application of Mosher’s method to the synthetic compounds allowed unequivocal absolute configuration assignment. While natural products and the synthetic intermediates were shown to be non-cytotoxic on the HCT116 cell line, the endochondral differentiation activity using human type X collagen transcription activity in ATDC5 cells is interesting.

Efficacy and Safety of mRNA SARS-CoV2 Vaccination in Heart Transplant Recipients

Purpose

Data on immunologic response to SARS-CoV2 vaccination in heart transplant recipients are scarce. We investigated the efficacy and safety of mRNA SARS-CoV2 vaccination in this patient population.

Methods

In a retrospective single-center study we included 54 consecutive adult heart transplant recipients who received 2 doses of mRNA SARS-CoV2 vaccine between January 1 and June 30, 2021. All patients were followed for 112±28 days after the second dose. At the end of follow-up we measured humoral response to SARS-CoV2 by assessing total antibody levels to the receptor-binding domain of SARS-CoV2 spike (S) protein using anti-RBD immunoassay. Anti-S antibody serum levels ≥250 BAU/mL were considered protective. At the same time, cellular response was measured by the IFN-γ response to S-peptide stimulation of recipient T lymphocyte populations. Protective cellular response was defined as more than 0,3% of IFN-γ responsive T cells.

Results

Of 54 recipients, 44 (81%) were male with a mean age of 63±8 years and a mean time from transplantation of 6.6±4.0 years. Immunosupressive regimen consisted of tacrolimus (mean C0 level 7.4±1.7 μg/mL), mycophenolate mofetil (mean dose 2120±419 mg) and steroids (mean dose 2.5±0.9 mg). The majority of patients received BTN162b2 vaccine (83%), and 17% of recipients were vaccinated with mRNA-1273. During follow-up, a humoral response was present in 24 (44%) of the recipients (median anti-S serum level 35.5 BAU/mL). We found no difference in humoral response between patients receiving BNT162b2 and mRNA-1273 vaccine (median anti-S serum level 68.3 BAU/mL vs. 15.5 BAU/mL, P=0.81). Protective humoral response was observed in 6 (11%) of the recipients (median anti-S serum level 557 BAU/mL). A cellular response to vaccine was present in 3 (6%) of the recipients; all 3 displayed a protective level of reponse. No recipients developed simultaneous protective humoral and cellular responses. Recipient age was the only predictor of protective humoral response (55±11 years in responders vs. 65±8 years in nonresponders; P=0.01). In 3 (6%) recipients we found worsening of allograft function requiring hospital admission, which occured within 1 month after receiving the second dose of vaccine.

Conclusion

In heart transplant recipients, mRNA SARS-CoV2 vaccination appears to be of limited efficacy and may, in some cases, be associated with worsening of allograft function.

Bioactive Bromotyrosine Derivatives from the Pacific Marine Sponge Suberea clavata (Pulitzer-Finali, 1982)

Chemical investigation of the South-Pacific marine sponge Suberea clavata led to the isolation of eight new bromotyrosine metabolites named subereins 1-8 (2-9) along with twelve known co-isolated congeners. The detailed configuration determination of the first representative major compound of this family 11-epi-fistularin-3 (11R,17S) (1) is described. Their chemical characterization was achieved by HRMS and integrated 1D and 2D NMR (nuclear magnetic resonance) spectroscopic studies and extensive comparison with literature data. For the first time, a complete assignment of the absolute configurations for stereogenic centers C-11/17 of the known members (11R,17S) 11-epi-fistularin-3 (1) and 17-deoxyfistularin-3 (10) was determined by a combination of chemical modifications, Mosher's technology, and ECD spectroscopy. Consequently, the absolute configurations of all our new isolated compounds 2-9 were determined by the combination of NMR, Mosher's method, ECD comparison, and chemical modifications. Interestingly, compounds 2-7 were obtained by chemical transformation of the major compound 11-epi-fistularin-3 (1). Evaluation for acetylcholinesterase inhibition (AChE), DNA methyltransferase 1 (DNMT1) modulating activity and antifouling activities using marine bacterial strains are also presented.

Quorum Sensing Inhibitory and Antifouling Activities of New Bromotyrosine Metabolites from the Polynesian Sponge Pseudoceratina n. sp

Four new brominated tyrosine metabolites, aplyzanzines C-F (1-4), were isolated from the French Polynesian sponge Pseudoceratina n. sp., along with the two known 2-aminoimidazolic derivatives, purealidin A (5) and 6, previously isolated, respectively, from the sponges Psammaplysilla purpurea and Verongula sp. Their structures were assigned based on the interpretation of their NMR and HRMS data. The compounds exhibited quorum sensing inhibition (QSi) and antifouling activities against several strains of bacteria and microalgae. To our knowledge, the QSi activity of this type of bromotyrosine metabolite is described here for the first time.

Bioactive Bromotyrosine-Derived Alkaloids from the Polynesian Sponge Suberea ianthelliformis

Herein, we describe the isolation and spectroscopic identification of eight new tetrabrominated tyrosine alkaloids 2⁻9 from the Polynesian sponge Suberea ianthelliformis, along with known major compound psammaplysene D (1), N,N-dimethyldibromotyramine, 5-hydroxy xanthenuric acid, and xanthenuric acid. Cytotoxicity and acetylcholinesterase inhibition activities were evaluated for some of the isolated metabolites. They exhibited moderate antiproliferative activity against KB cancer cell lines, but psammaplysene D (1) displayed substantial cytotoxicity as well as acetylcholinesterase inhibition with IC50 values of 0.7 μM and 1.3 μM, respectively.

Ilimaquinone and 5-epi-Ilimaquinone: Beyond a Simple Diastereomeric Ratio, Biosynthetic Considerations from NMR-Based Analysis

Dactylospongia metachromia and Dactylospongia elegans collected from French Polynesia were studied with a particular focus on the variation of the diastereomeric ratio between ilimaquinone (4) and 5-epi-ilimaquinone (5). More than 100 samples, covering an area of 4100 km2, were studied to try to clarify this intriguing issue. Nuclear magnetic resonance appeared as the non-destructive, straightforward technique of choice for a relative quantitative study. A random distribution, unique at that point in nature, is observed and leads to biosynthetic considerations. Biological evaluation of both compounds was also performed and showed moderate discrepancies in cytotoxicity and apoptosis induction.

Cytotoxic Guanidine Alkaloids from a French Polynesian Monanchora n. sp. Sponge

Four bicyclic and three pentacyclic guanidine alkaloids (1-7) were isolated from a French Polynesian Monanchora n. sp. sponge, along with the known alkaloids monalidine A (8), enantiomers 9-11 of known natural product crambescins, and the known crambescidins 12-15. Structures were assigned by spectroscopic data interpretation. The relative and absolute configurations of the alkaloids were established by analysis of (1)H NMR and NOESY spectra and by circular dichroism analysis. The new norcrambescidic acid (7) corresponds to interesting biosynthetic variation within the pentacyclic core. All compounds exhibited antiproliferative and cytotoxic efficacy against KB, HCT116, HL60, MRC5, and B16F10 cancer cells, with IC50 values ranging from 4 nM to 10 μM.

Quorum sensing inhibitors from Leucetta chagosensis Dendy, 1863

Sponges are a rich source for investigation of bioactive small molecules. They have been mostly investigated for the search of new pharmacological models or therapeutic agents for the treatment of human diseases. Micro-organisms can also represent a virulent pathogen for marine invertebrates such as sponges, which need to protect themselves against these microbes. Sponges' self defence mechanisms involving dialogue molecules thus represent a pertinent research track for potent anti-infective and anti-biofilm activities such as quorum sensing inhibitors (QSIs). The investigation of the QSI crude extract of Leucetta chagosensis Dendy, 1863 led to the isolation of three new alkaloids, isonaamine D, di-isonaamidine A and leucettamine D, along with the known isonaamine A and isonaamidine A. Isonaamidine A and isonaamine D were identified as inhibitors of the three quorum sensing pathways of Vibrio harveyi (CAI-1, AI-2 and harveyi auto inducer), but isonaamidine A displayed the strongest activity on AI-2 biosensor. Both compounds are new examples of natural QSIs of V. harveyi. These results outline the importance of these secondary metabolites for their producing organisms themselves in their natural environment, as well as the potential of the marine resource for aquaculture needs.

SIGNIFICANCE AND IMPACT OF THE STUDY

A new type of quorum sensing inhibitors was isolated from the sponge Leucetta chagosensis. One of them inhibits strongly the AI-2 channel of Vibrio harveyi, a marine pathogen of special importance in aquaculture. The activity of five different related compounds, including three new natural products discovered there, was investigated leading to structure-activity relationships which are useful for the design of new quorum sensing inhibitors to control marine infectious pathogens.

Plakilactones from the marine sponge Plakinastrella mamillaris. Discovery of a new class of marine ligands of peroxisome proliferator-activated receptor γ

In this paper we report the isolation and the molecular characterization of a new class of PPARγ ligands from the marine environment. Biochemical characterization of a library of 13 oxygenated polyketides isolated from the marine sponge Plakinastrella mamillaris allowed the discovery of gracilioether B and plakilactone C as selective PPARγ ligands in transactivation assays. Both agents covalently bind to the PPARγ ligand binding domain through a Michael addition reaction involving a protein cysteine residue and the α,β-unsaturated ketone in their side chains. Additionally, gracilioether C is a noncovalent agonist for PPARγ, and methyl esters 1 and 2 are noncovalent antagonists. Structural requirements for the interaction of these agents within the PPARγ ligand binding domain were obtained by docking analysis. Gracilioether B and plakilactone C regulate the expression of PPARγ-dependent genes in the liver and inhibit the generation of inflammatory mediators by macrophages.

Pipestelides A-C: cyclodepsipeptides from the Pacific marine sponge Pipestela candelabra

Pipestelides A-C (2-4) are three new NRPS-PKS hybrid macrolides containing uncommon moieties, isolated from the Pacific marine sponge Pipestela candelabra. Their structures were elucidated on the basis of spectroscopic data. These cyclodepsipeptides appear to be biosynthetically related to jaspamide (aka jasplakinolide) (1) by chemical modification of the building blocks of the polyketide or peptide chains. Pipestelides A-C (2-4) contain a bromotyrosine [3-amino-3-(bromo-4-hydroxyphenyl)propanoic acid] unit, a polypropionate with a Z double bond, and a 2-hydroxyquinolinone, respectively. Revised chemical shift assignments are provided for the co-isolated known jasplakinolide C(a) (5). In addition, compounds 2 and 3 exhibited cytotoxic activities in the micromolar range.

4-Methylenesterols from Theonella swinhoei sponge are natural pregnane-X-receptor agonists and farnesoid-X-receptor antagonists that modulate innate immunity

We report the isolation and the structural elucidation of a family of polyhydroxylated steroids from the marine sponge Theonella swinhoei. Decodification of interactions of these family with nuclear receptors shows that these steroids are potent agonists of human pregnane-X-receptor (PXR) and antagonists of human farnesoid-X-receptor (FXR) with the putative binding mode to nuclear receptors (NRs) obtained through docking experiments. By using monocytes isolated from transgenic mice harboring hPXR, we demonstrated that swinhosterol B counter-regulates induction of pro-inflammatory cytokines in a PXR-dependent manner. Exposure of CD4(+) T cells to swinhosterol B upregulates the expression of IL-10 causing a shift toward a T cells regulatory phenotype in a PXR dependent manner. These results pave the way to development of a dual PXR agonist/FXR antagonist with a robust immunomodulatory activity and endowed with the ability to modulate the expression of bile acid-regulated genes in the liver.

The in vivo anti-plasmodial activity of haliclonacyclamine A, an alkaloid from the marine sponge, Haliclona sp

The compound haliclonacyclamine A was isolated from the Haliclona sponge at Solomon Islands. It acts as a powerful in vitro and in vivo anti-plasmodial agent against the chloroquine-resistant Plasmodium falciparum strain FCB1and Plasmodium vinckei petteri-infected mice, respectively.

Bioactive indole derivatives from the South Pacific marine sponges Rhopaloeides odorabile and Hyrtios sp

Indole derivatives including bromoindoles have been isolated from the South Pacific marine sponges Rhopaloeides odorabile and Hyrtios sp. Their structures were established through analysis of mass spectra and 1D and 2D NMR spectroscopic data. Their potential inhibitory phospholipase A₂ (PLA₂), antioxidant and cytotoxic activities were evaluated. The new derivative 5,6-dibromo-L-hypaphorine (9) isolated from Hyrtios sp. revealed a weak bee venom PLA₂ inhibition (IC₅₀ 0.2 mM) and a significant antioxidant activity with an Oxygen Radical Absorbance Capacity (ORAC) value of 0.22. The sesquiterpene aureol (4), also isolated from Hyrtios sp., showed the most potent antioxidant activity with an ORAC value of 0.29.

Towards new ligands of nuclear receptors. Discovery of malaitasterol A, an unique bis-secosterol from marine sponge Theonella swinhoei

Malaitasterol A, an unprecedented bis-secosterol, was isolated from a Solomon collection of Theonella swinhoei. The structure was elucidated on the basis of a combination of comprehensive 1D and 2D NMR analysis, high-resolution mass spectrometry and DFT (13)C chemical shift calculations. The biological characterization of malaitasterol A provided evidence that this compound is a potent agonist of pregnane-X-receptor and its putative binding mode to PXR has been obtained through docking calculations.

Solomonsterols A and B from Theonella swinhoei. The first example of C-24 and C-23 sulfated sterols from a marine source endowed with a PXR agonistic activity

The finding of new PXR modulators as potential leads for treatment of human disorders characterized by dysregulation of innate immunity and with inflammation is of wide interest. In this paper, we report the identification of the first example of natural marine PXR agonists, solomonsterols A and B, from a Theonella swinhoei sponge. The structures were determined by interpretation of NMR and ESIMS data, and the putative binding mode to PXR has been obtained through docking calculations.

Agelastatin E, agelastatin F, and benzosceptrin C from the marine sponge Agelas dendromorpha

The study of the n-butanol extract of the New Caledonian sponge Agelas dendromorpha led to the isolation and identification of three new pyrrole-2-aminoimidazole (P-2-AI) alkaloids, named agelastatins E (3) and F (4) and benzosceptrin C (5), together with 10 known metabolites, agelastatin A (1), agelastatin D (2), sceptrin (6), manzacidin A, tauroacidin A, taurodispacamide A, nortopsentin D, thymine, longamide, and 4,5-dibromopyrrole-2-carboxamide. Their structures were assigned by spectroscopic data interpretation. All the compounds were tested for cytotoxic activity.

Homophymines B-E and A1-E1, a family of bioactive cyclodepsipeptides from the sponge Homophymia sp

Nine new cyclodepsipeptides, homophymines B-E (2-5) and A1-E1 (1a-5a), were isolated from the polar extracts of the sponge Homophymia sp. The new structures, featuring new polyketide-derived end groups, were determined by interpretation of NMR and MS data. The configurations of the new end groups was secured by the application of J-based configurational analysis. Homophymines displayed very potent antiproliferative activity (IC(50) in the nM range) against a panel of human cancer cell lines.

Agelasines J, K, and L from the Solomon Islands Marine Sponge Agelas cf. mauritiana

Three new diterpene alkaloids, agelasine J (3), agelasine K (4), and agelasine L (5), were isolated from the marine sponge Agelas cf. mauritiana collected in the Solomon Islands. The structures of these compounds were elucidated by physical data analyses. They displayed in vitro antimalarial activity against Plasmodium falciparum.

Homophymine A, an anti-HIV cyclodepsipeptide from the sponge Homophymia sp

A new anti-HIV cyclodepsipeptide, homophymine A, was isolated from a New Caledonian collection of the marine sponge Homophymia sp. The structure of homophymine A was determined by interpretation of spectroscopic data, acid hydrolysis, and LC-MS analysis. Homophymine A contains 11 amino acid residues and an amide-linked 3-hydroxy-2,4,6-trimethyloctanoic acid moiety. Along with four D-, two L-, and one N-methyl amino acids, it also contains four unusual amino acid residues: (2S,3S,4R)-3,4-diMe-Gln, (2R,3R,4S)-4-amino-2,3-dihydroxy-1,7-heptandioic acid, L-ThrOMe, and (2R,3R,4R)-2-amino-3-hydroxy-4,5-dimethylhexanoic acid. In a cell-based XTT assay, homophymine A exhibited cytoprotective activity against HIV-1 infection with a IC50 of 75 nM.

Synthesis and antibacterial activity of mechanism-based inhibitors of KDO8P synthase and DAH7P synthase

KDO8PS (3-deoxy-D-manno-2-octulosonate-8-phosphate synthase) and DAH7PS (3-deoxy-D-arabino-2-heptulosonate-7-phosphate synthase) are attractive targets for the development of new anti-infectious agents. Both enzymes appear to proceed via a common mechanism involving the reaction of phosphoenolpyruvate (PEP) with arabinose 5-phosphate or erythrose-4-phosphate, to produce the corresponding ulosonic acids, KDO8P and DAH7P, respectively. The synthesis of new inhibitors closely related to the supposed tetrahedral intermediate substrates for the enzymes is described. The examination of the antibacterial activity of these derivatives is reported.