Biology subjects

Stien, D.

Publications and source records attributed to Stien, D..

3 recordsLinked to original sources

bioRxiv2026

Metabolomic and Transcriptomic rewiring between virus resistance and susceptibility in Ostreococcus mediterraneus

The genus Ostreococcus, comprising picoeukaryotic unicellular algae, plays a key role in many coastal marine ecosystems. These phytoplankton are infected by lytic double-stranded DNA prasinoviruses against whom they have the capacity to reliably evolve stable antiviral resistance. Regulation of virus resistance and susceptibility is hypothesized to arise through a phenotypic switch, as resistant cell lines can be isolated from susceptible lines after viral exposure and vice versa. To elucidate the molecular mechanisms underlying this resistance, we integrated untargeted metabolomic analyses and transcriptomics in virus-resistant and virus-susceptible lines of O. mediterraneus. Transcriptomic analyses corroborated previous findings in O. tauri, revealing that most gene expression changes were concentrated on a single chromosome. Specifically, a [~]530 kb region was over-transcribed in virus-resistant lines, while a distinct [~]110 kb region was over-expressed in virus-susceptible lines. Comparative metabolomics identified several oxidized galactolipids and oxidized sterols as biomarkers of the susceptible phenotype, while fewer biomarkers were identified for the resistant phenotype. By integrating transcriptomic and metabolomic signatures--focusing on the expression of genes within biosynthetic pathways linked to these metabolite biomarkers--we uncovered candidate molecular mechanisms underlying the cellular physiology of susceptible versus resistant phenotypes. Authors SummaryViruses are the most abundant biological entities in the ocean, shaping the dynamics of phytoplankton communities that underpin marine food webs. Ostreococcus, one of the smallest photosynthetic eukaryotes, is frequently infected by highly abundant prasinoviruses in its natural environment. In this study, we aimed to understand the physiological bases of virus-resistant and susceptible Ostreococcus mediterraneus lines. We compared gene expression and untargeted metabolite profiles between a resistant line and a susceptible line derived from it. The metabolic profiles were much more variable between replicates than the transcriptomic profiles and the most differentially expressed genes did not include those involved in the biosynthetic pathways of the metabolite biomarkers identified. We estimated the congruence between the metabolomes and transcriptomes as the percent of relative expression changes fitting to the relative change in the metabolite. This study provides evidence of the subtle links between gene expression and metabolomic signatures and the importance of integrating multiple levels of cellular processes.

microbiology↗

bioRxiv2021

Integrated metabolomic, molecular networking and genome mining analyses uncover novel angucyclines from Streptomyces sp. RO-S4 isolated from Bejaia Bay, Algeria

Multi-omic approaches have recently made big strides towards the effective exploration of microorganisms and accelerating the discovery of new bioactive compounds. We combined metabolomic, molecular networking, and genomic-based approaches to investigate the metabolic potential of the Streptomyces sp. RO-S4 strain isolated from the polluted waters of Bejaia Bay in Algeria. Antagonistic assays against methicillin-resistant Staphylococcus aureus with RO-S4 organic extracts showed an inhibition zone of 20 mm by the agar diffusion method, and its minimum inhibitory concentration was 16 g/mL. A molecular network was created using GNPS and annotated through the comparison of MS/MS spectra against several databases. The predominant compounds in the RO-S4 extract belonged to the angucyclines family. Three compounds were annotated as known metabolites, while all the others were putatively new to Science. Notably, all compounds had fridamycin-like aglycones, and several of them had a lactonized D ring analogous to that of urdamycin L. The whole genome of Streptomyces RO-S4 was sequenced to identify the biosynthetic gene cluster (BGC) encoding for these angucyclines, which yielded a draft genome of 7,497,846 bp with 72.4% G+C content. Subsequently, a genome mining analysis revealed 19 putative biosynthetic gene clusters, including a grincamycin-like BGC with a high similarity to that of Streptomyces sp. CZN-748 previously reported to also produce mostly open fridamycin-like aglycones. As the ring-opening process leading to these compounds is still not defined, we performed comparative analysis with other angucycline BGCs and advanced some hypotheses to explain the ring-opening and lactone formation, possibly linked to the uncoupling between the activity of GcnE and GcnM homologues in the RO-S4 strain. The combination of metabolomic and genomic approaches greatly improved the interpretation of the metabolic potential of the RO-S4 strain.

microbiology↗

bioRxiv2020

Effect of 10 UV filters on the brine shrimp Artemia salina and the marine microalgae Tetraselmis sp.

The presence of pharmaceutical and personal care products (PPCPs) residues in the aquatic environment is an emerging issue due to their uncontrolled release, through grey water, and accumulation in the environment that may affect living organisms, ecosystems and public health. The aim of this study is to assess the toxicity of benzophenone-3 (BP-3), bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), butyl methoxydibenzoylmethane (BM), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), 2-Ethylhexyl salicylate (ES), diethylaminohydroxybenzoyl hexyl benzoate (DHHB), diethylhexyl butamido triazone (DBT), ethylhexyl triazone (ET), homosalate (HS), and octocrylene (OC) to marine organisms from two major trophic levels including autotrophs (Tetraselmis sp.) and heterotrophs (Artemia salina). In general, EC50 results show that both HS and OC are the most toxic for our tested species, followed by a significant effect of BM on Artemia salina but only at high concentrations (1 mg/L) and then an effect of ES, BP3 and DHHB on the metabolic activity of the microalgae at 100 g/L. BEMT, DBT, ET, MBBT had no effect on the tested organisms, even at high concentrations (2mg/L). OC toxicity represent a risk for those species since it is observed at concentrations only 15 to 90 times higher than the highest concentrations reported in the natural environment and HS toxicity is for the first time reported on microalgae and was very important on Tetraselmis sp. at concentrations close to the natural environment concentrations.

ecology↗