Marine fungal community composition and diversity across a polluted site in the south Mediterranean coast: the Monastir Bay, Tunisia.

Marine fungi communities play a crucial role in the recycling of nutrients, restoration of biological systems, and the overall functioning of ecosystems. While aquatic fungal communities do react to pollution, there is a significant lack of information regarding the changes in the fungal community's structure, caused by marine pollution. In this study, we aim to address this gap in knowledge by investigating the range and makeup of fungal species present in marine environments in a polluted bay in Tunisia, spanning a biodiversity hotspot (Monastir Bay). Sequence analysis of the internal transcribed spacer region from culturable mycobiome and physicochemical parameters were investigated at seven sites in the bay. A total of 32 fungal taxa were identified at the genus and/or species levels and were assigned to four major groups (Aspergillacae 37.5%, Dothiomyceta 21.87%, Sordariamyceta 28.12%, and Yeasts 12.5%) with a remarkable predominance of Aspergillus genus. Assessment of the Shannon-Wiener diversity index and the Simpson dominance index revealed that the highest species diversity index (0.84) was recorded at the Kheniss site. Our results suggest the existence of diverse fungal communities, can be considered a useful community model for further ecological and evolutionary study of fungi in the bay.

A review on microbial contamination cases in Tunisian coastal marine areas.

Microbial pollution in marine environments is one of the critical issues with regard to the sanitary status of recreational activities and seafood harvesting due to a potential contamination by pathogenic microorganisms. This review's objectives were to identify instances of bacterial, viral and protozoan parasite pollution in the Tunisian coastal region and to make recommendations for further research. Fecal indicators such as Escherichia coli and Salmonella spp. were detected in samples of clams and mussels. Vibrionaceae species were also recorded in seawater, sediment, fish and clams in different sites from north to south with the dominance of Vibrio alginolyticus. Bivalve mollusks collected from the Tunisian coast have been revealed to harbor viruses as well as protozoan parasites. Furthermore, the isolation of multidrug-resistant bacterial strains from Tunisian coastlines proves the significant spread and circulation of antibiotic resistance caused by the massive use of antibiotics. In conclusion, we suggest intensive monitoring and cutting-edge wastewater treatment technologies to enhance seawater quality and preserve the biodiversity of aquatic life. Rapid detection techniques for the most important pathogenic microorganisms in seafood and seawater must be also developed to reduce human health risk.

Morphometric Variation among Four Local Ruditapes decussatus Populations in Monastir Bay (Eastern Coast, Tunisia)

Abstract In Tunisia, Monastir bay, extending for 38 km along the eastern coast of Tunisia, harbors different species of bivalves such as the clam Ruditapes decussatus, a species of major socio-economic interest. Despite its importance, no studies have been carried out about the morphology of this mollusc in Monastir bay. Thus, the current study aimed to analyze the shell morphological variations in the European clamRuditapes decussatus from Monastir Bay coast. The comparison of the shell shape of individuals from different populations was performed based on samples taken at four different sites (Khniss, Ksiba, Bkalta and Sokrine). Variance analysis of the morphometric indices (elongation, compactness, convexity and density) for the four populations indicated significant differences among sites with (p=0<0.05). Principal component analysis (PCA) revealed two intra-population groups for Sokrine site, supporting an intra-population variation in the shell morphology. Allometric relationships established between linear variables (shell length, height and width) and ponderal variables (total weight, shell weight) as well as the relative growth between variables (isometry vs. allometry) were analyzed. All morphometric relationships were highly significant (P<0.001) with high correlation coefficients (R2: 0.714-0.982), showing positive allometric growth for Bkalta and negative allometric growth for Sokrine. The data obtained will be useful in research studies and have practical application in diverse research fields such as biology, ecology, fisheries assessment and management.

First report of Tunisian coastal water contamination by protozoan parasites using mollusk bivalves as biological indicators.

In order to establish seawater contamination by emerging protozoan parasites, we used qPCR to molecularly characterize and evaluate the parasitic burden of Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii, and Cyclospora cayetanensis in 1255 wild bivalve mollusks collected along the Tunisian coasts. T. gondii, G. duodenalis and C. cayetanensis were detected in 6.9% (99% CI=1.6-12.2%) pools of Ruditapes decussatus. None of the samples were found positive to Cryptosporidium spp.; 6.6% pools of R. decussatus were positive for T. gondii Type I, 1.6% for G. duodenalis assemblage A, and 1.6% for the association T. gondii Type I/C. cayetanensis/G. duodenalis assemblage A. R. decussatus harbored up to 77500 oocysts/sample of T. gondii, up to 395 cysts/sample of G. duodenalis, and 526 oocysts/sample of C. cayetanensis. These results provide the first evidence that the Tunisian coasts are contaminated by zoonotic protozoan parasites that can constitute a direct or indirect risk for human health.

Evaluation of cytotoxicity and biological activities in extracellular polysaccharides released by cyanobacterium Arthrospira platensis

The aim of this work was to evaluate the cytotoxicity of Arthrospira platensis Extracellular Polymeric Substances (EPS) for colon cancer and kidney cell lines. Results showed that EPS were free from cytotoxic effects. A variety of solvents were assessed for their ability to extract the bioactive ingredients from EPS. Methanol gave the highest yield (75.75 percent) than other solvents. The extracts were tested for activities against a collection of Gram+/- bacteria. The methanol extract exhibited a more potent activity than the other organic extracts, whereas the aqueous extract was active against Staphylococcus epidermis (Gram+) and Salmonella typhimurium (Gram-). Finally, The extracts were also tested for the antioxidant activity, using the Trolox Equivalent Antioxidant Activity assay. The methanol extract displayed a moderate antioxidant activity (TEAC = 0.027 mg/ml). The HPLC analysis of this extract revealed two distinct peaks: 8.1 kDa (8.31 min) and 4.1 kDa (8.54 min).