Effect of Acidic Industrial Effluent Release on Microbial Diversity and Trace Metal Dynamics During Resuspension of Coastal Sediment

Both industrial effluent discharge and the resuspension of contaminated marine sediments are important sources of trace metals in seawater which potentially affect marine ecosystems. The aim of this study was to evaluate the impact of the industrial wastewaters having acidic pH (2–3) and containing trace metals on microbial diversity in the coastal ecosystem of the Gulf of Gabès (Tunisia, southern Mediterranean Sea) subjected to resuspension events of marine sediments. Four trace elements (As, Cd, U, and V) were monitored during 10-day sediment resuspension experiments. The highest enrichment in the seawater dissolved phase was observed for Cd followed by U, V, and As. Cd remobilization was improved by indigenous microbial community, while U release was mainly abiotic. Acidic effluent addition impacted both trace metal distribution and microbial diversity, particularly that of the abundant phylum Bacteroidetes. Members of the order Saprospirales were enriched from sediment in natural seawater (initial pH > 8), while the family Flavobacteriaceae was favored by acidified seawater (initial pH < 8). Some Flavobacteriaceae members were identified as dominant species in both initial sediment and experiments with acidic wastewater, in which their relative abundance increased with increasing dissolved Cd levels. It could be therefore possible to consider them as bioindicators of metal pollution and/or acidification in marine ecosystems

Etude de la pollution par hydrocarbures des sédiments côtiers de la région de Sfax (chenal Sfax-Kerkennah)

PARIS-BIUSJ-Physique recherche (751052113) / SudocPARIS-Museum-Bib. Botanique (751052309) / SudocSudocFranceF

The Tunisian Mediterranean coastline: potential threats from urban discharges Sfax-Tunisian Mediterranean coasts

International audienc

Production of Poly(3-Hydroxybutyrate) by Haloarcula, Halorubrum, and Natrinema Haloarchaeal Genera Using Starch as a Carbon Source

Microbial production of bioplastics, derived from poly(3-hydroxybutyrate) (PHB), have provided a promising alternative towards plastic pollution. Compared to other extremophiles, halophilic archaea are considered as cell factories for PHB production by using renewable, inexpensive carbon sources, thus decreasing the fermentation cost. This study is aimed at screening 33 halophilic archaea isolated from three enrichment cultures from Tunisian hypersaline lake, Chott El Jerid, using starch as the sole carbon source by Nile Red/Sudan Black staining and further confirmed by PCR amplification of phaC and phaE polymerase genes. 14 isolates have been recognized as positive candidates for PHA production and detected during both seasons. The identification of these strains through 16S rRNA gene analyses showed their affiliation to Halorubrum, Natrinema, and Haloarcula genera. Among them, three PHB-producing strains, CEJ34-14, CEJ5-14, and CEJ48-10, related to Halorubrum chaoviator, Natrinema pallidum, and Haloarcula tradensis were found to be the best ones reaching values of 9.25, 7.11, and 1.42% of cell dry weight (CDW), respectively. Our findings highlighted that Halorubrum, Natrinema, and Haloarcula genera were promising candidates for PHB production using soluble starch as a carbon source under high salinity (250 g L-1 NaCl)

Sources and distribution of aliphatic and polyaromatic hydrocarbons in sediments of Sfax, Tunisia, Mediterranean Sea

International audienceThis investigation is the first extensive study of the spatial distribution and sources of hydrocarbons in surface sediments from the Sfax-Kerkennah coastal zone (Tunisia). We show that the Sfax-Kerkennah coastal zone suffers from serious problems of pollution due to petroleum contamination. Analyses performed by GC/FID and GC/MS permitted a precise determination of both aliphatic and alicyclic compounds (n-alkanes, isoprenoids, hopanes, steranes, diasteranes and unresolved complex mixture of fossil hydrocarbons and highly degraded organic matter (UCM)) and polycyclic aromatic hydrocarbons (PAHs). Non-aromatic hydrocarbon concentrations vary in the range = 16-1729 μg/g sediment d.w., and PAH concentrations vary in the range = 0.11-10.72 μg/g sediment d.w. These concentrations are relatively high, compared to other Mediterranean sites (37 examined sites). n-Alkane, UCM and PAH concentrations with biomarker profiles together prove the presence of a limited petrogenic contamination in sediments close to the Kerkennah Island, 22 km from the harbour of Sfax. In contrast, moderate to high petrogenic contamination is detected in the Sfax area sediments, notably closer to the storage tanks of hydrocarbons. Contaminant patterns indicate that PAHs originate mainly from fossil sources, with higher pyrolytic contributions near industrialized and urban areas. GC/MS analyses indicate the omnipresent contamination by petroleum. This contamination is confirmed by the identification of hopanes with predominant C 29 and C 30 α,β compounds and steranes with predominance of C 29, C 28 and C 27 compounds

A Bioinformatic Study on the Potential Anti-Vitiligo Activity of a <i>Carpobrotus edulis</i> Compound

The plant Carpobrotus edulis has traditionally been known for its wide applications in diseases, especially vitiligo, which is characterized by patches and white macules caused by the loss of melanocytes. One of the chemical treatments for vitiligo consists mainly of skin repigmentation and usually leads to a non-durable effect by inhibiting the Janus kinase (JAK) signal transduction (STAT pathway). JAK inhibitors generally block multiple JAK tyrosine kinases, which leads to secondary effects. In this study, natural molecules from Carpobrotus edulis were extracted and tested using a structure-based drug-design approach and pharmacophore modeling. The best-fit candidate from the extracted molecules was compared to the chemical molecules used. The results indicated a similarity between the chemical and natural ligands which suggested the potential use of the natural product against vitiligo. The main finding of this research work was the discovery of a new molecule extracted from a natural plant and the detection of its anti-vitiligo activity using an in-silico approach. This method can significantly reduce the cost of searching for potential medicinal molecules

Hydrocarbons in surface sediments from the Sfax coastal zone, (Tunisia) Mediterranean Sea

International audienceThe Semi-enclosed Mediterranean Sea records various signals of high anthropic pressures from surrounding countries and the industrialized European countries. This is particularly true for oil pollution. Although accounting for 1% of the world's ocean surface, it receives about 25% of the petroleum inputs to the ocean. To achieve a global budget we need to collect information from different parts of the Mediterranean. Particularly, we focus in this paper on the Southern Mediterranean, where data are presently very scarce. In this context, the University of Sfax has undertaken an estimation of hydrocarbon pollution along the coasts of Sfax and Gabès Gulf. Non-aromatic hydrocarbons were analysed in 8 surface sediments by FT/IR and GC/MS. Non-aromatic hydrocarbon concentrations vary in the range 310-1406 μg g -1 sediments dry weight, which is high, compared to other Mediterranean sites. GC/MS data indicate a large group of unresolved compounds suggesting a petroleum contamination, confirmed by the identification of hopanes with predominant C 29 and C 30 α,β compounds and steranes with predominance of C 27 over C 28 and C 29 compounds

Evaluation of hydrocarbon pollution in marine sediments of Sfax coastal areas from the Gabes Gulf of Tunisia, Mediterranean Sea

International audienc

Effect and removal of bisphenol A by two extremophilic microalgal strains (Chlorophyta)

International audienceThe effects and the removal efficiency of bisphenol A (BPA) on two extremophilic Chlorophyta strains, an alkaliphilic Picocystis and a thermophilic Graesiella, were assessed. BPA was shown to inhibit the growth and photosynthesis of both species, but to a greater extent for Graesiella. The growth IC50 (4 days) was 32 mg L-1 for Graesiella and higher than 75 mg L-1 for Picocystis. Oxidative stress was induced in both strains when exposed to increasing BPA concentrations, as evidenced by increased malondialdehyde content. BPA exposure also resulted in an over-expression of antioxidant activities (ascorbate peroxidase, glutathione S-transferase and catalase) in Picocystis whereas they were repressed in Graesiella. Both species exhibited high BPA removal efficiency, reaching 72% for Picocystis and 52.6% for Graesiella at 25 mg L-1 . BPA removal was mostly attributed to biodegradation for both species. Overall, according to its extended tolerance and its removal capacity, Picocystis appeared to be a promising species for the BPA bioremediation even at high contamination levels

Origin and distribution of hydrocarbons and organic matter in the surficial sediments of the Sfax-Kerkennah channel (Tunisia, Southern Mediterranean Sea)

International audienceWe investigated the origin and distribution of aliphatic and polycyclic aromatic hydrocarbons (AHs and PAHs)and organic matter (OM) in surficial sediments of the Sfax-Kerkennah channel in the Gulf of Gabès (Tunisia,Southern Mediterranean Sea). TOC, AH and PAH concentrations ranged 2.3–11.7%, 8–174 μg g−1 sed. dw and175–10,769 ng g−1 sed. dw, respectively. The lowest concentrations were recorded in the channel (mediumsand sediment) and the highest ones in the Sfax harbor (very fine sand sediment). AHs, PAHs and TOC werenot correlated for most of the stations. TOC/N and δ13C values revealed a mixed origin of OM with both marineand terrestrial sources. Hydrocarbon molecular composition highlighted the dominance of petrogenic AHs andthe presence of both petrogenic and pyrogenic PAHs, associated with petroleum products and combustion processes.This work underscores the complex distribution patterns and the multiple sources of OM and hydrocarbonsin this highly anthropogenized coastal environment