Phytoplanktonic species in the haloalkaline Lake Dziani Dzaha select their archaeal microbiome.

Microorganisms are key contributors of aquatic biogeochemical cycles but their microscale ecology remains largely unexplored, especially interactions occurring between phytoplankton and microorganisms in the phycosphere, that is the region immediately surrounding phytoplankton cells. The current study aimed to provide evidence of the phycosphere taking advantage of a unique hypersaline, hyperalkaline ecosystem, Lake Dziani Dzaha (Mayotte), where two phytoplanktonic species permanently co-dominate: a cyanobacterium, Arthrospira fusiformis, and a green microalga, Picocystis salinarum. To assay phycospheric microbial diversity from in situ sampling, we set up a flow cytometry cell-sorting methodology for both phytoplanktonic populations, coupled with metabarcoding and comparative microbiome diversity.

Diagnostic Performance of F-Choline Positron Emission Tomography/Contrast-Enhanced Computed Tomography in Adenoma Detection in Primary Hyperparathyroidism after Inconclusive Imaging: A Retrospective Study of 215 Patients.

This large, retrospective, single-centre study evaluated the diagnostic performance of F-choline positron emission tomography/contrast-enhanced computed tomography (PET/ceCT) in preoperative parathyroid adenoma detection in primary hyperparathyroidism cases after negative/inconclusive ultrasound or other imaging findings. We included patients who underwent surgery and F-choline PET/ceCT for inconclusive imaging results between 2015 and 2020. We compared the F-choline PET/ceCT results with surgical and histopathological findings and identified the variables influencing the correlation between F-choline PET/ceCT and surgical findings.

Do microbial planktonic communities reflect the ecological changes of Glorieuses coral reefs (Iles Eparses, Western Indian Ocean)?

Ecological baselines for the structure and functioning of ecosystems in the absence of human activity can provide essential information on their health status. The Glorieuses islands are located in the Western Indian Ocean (WIO) and can be considered as "pristine" ecosystems that have not been subjected to anthropogenic pressure. Their nutrient context and the microbial assemblages were assessed by determining the abundance of heterotrophic prokaryotes (archaea and bacteria), picocyanobacteria, picoeukaryotes, microphytoplankton and protozooplankton communities in five stations, during two contrasted periods (November 2015 and May 2016).

Alterins Produced by Oyster-Associated Are Antibacterial Cyclolipopeptides with LPS-Binding Activity.

Discovery after discovery, host-associated microbiota reveal a growing list of positive effects on host homeostasis by contributing to host nutrition, improving hosts' immune systems and protecting hosts against pathogens. In that context, a collection of oyster associated bacteria producing antibacterial compounds have been established to evaluate their role in non-host-derived immunity. Here, we described alterins; potent anti-Gram negative compounds produced by h-6 and h-42 isolated from different healthy oyster hemolymph.

ID15A at the ESRF - a beamline for high speed operando X-ray diffraction, diffraction tomography and total scattering.

ID15A is a newly refurbished beamline at the ESRF devoted to operando and time-resolved diffraction and imaging, total scattering and diffraction computed tomography. The beamline is optimized for rapid alternation between the different techniques during a single operando experiment in order to collect complementary data on working systems. The high available energy (up to 120 keV) means that even bulky and highly absorbing systems may be studied.

Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta).

Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean = 652 ± 179 μg chlorophyll a L). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities.

Spatiotemporal variations in microbial diversity across the three domains of life in a tropical thalassohaline lake (Dziani Dzaha, Mayotte Island).

Thalassohaline ecosystems are hypersaline environments originating from seawater in which sodium chloride is the most abundant salt and the pH is alkaline. Studies focusing on microbial diversity in thalassohaline lakes are still scarce compared with those on athalassohaline lakes such as soda lakes that have no marine origin. In this work, we investigated multiple facets of bacterial, archaeal and eukaryotic diversity in the thalassohaline Lake Dziani Dzaha using a metabarcoding approach.

Structural and functional responses of coastal marine phytoplankton communities to PAH mixtures.

The toxicity of polycyclic aromatic hydrocarbons (PAHs) mixtures was evaluated on natural phytoplankton communities sampled from lagoons of Bizerte (South-western Mediterranean Sea) and Thau (North-western Mediterranean Sea). PAHs induced short-term dose and ecosystem-dependant decreases in photosynthetic potential. Chlorophyll a was negatively affected by increasing PAHs concentrations, together with dramatic changes in phytoplankton community composition.

Inefficient immune response is associated with microbial permissiveness in juvenile oysters affected by mass mortalities on field.

Since 2008, juvenile Crassostrea gigas oysters have suffered from massive mortalities in European farming areas. This disease of complex etiology is still incompletely understood. Triggered by an elevated seawater temperature, it has been associated to infections by a herpes virus named OsHV-1 as well as pathogenic vibrios of the Splendidus clade.

Corallivory and the microbial debacle in two branching scleractinians.

The grazing activity by specific marine organisms represents a growing threat to the survival of many scleractinian species. For example, the recent proliferation of the corallivorous gastropod Drupella now constitutes a critical case in all South-East Asian waters. If the damaging effects caused by this marine snail on coral polyps are relatively well known, the indirect incidence of predation on coral microbial associates is still obscure and might also potentially impair coral health.

Microbial Diversity and Cyanobacterial Production in Dziani Dzaha Crater Lake, a Unique Tropical Thalassohaline Environment.

This study describes, for the first time, the water chemistry and microbial diversity in Dziani Dzaha, a tropical crater lake located on Mayotte Island (Comoros archipelago, Western Indian Ocean). The lake water had a high level of dissolved matter and high alkalinity (10.6-14.

Trophic relationships between metazooplankton communities and their plankton food sources in the Iles Eparses (Western Indian Ocean).

Coral reef and atoll lagoons are among the most diversified marine ecosystems but also the most affected by the combined effects of climate change and human activities. The Iles Eparses (Scattered Islands) in the Western Indian Ocean have been little affected by human pressure and can be considered to be "pristine" ecosystems. Metazooplankton plays a major role in the functioning and productivity of aquatic ecosystems, and this study was undertaken: (i) to determine the spatial abundance, distribution and species composition of metazooplankton, (ii) to assess the effect of metazooplankton grazing on pico- and nanophytoplankton and (iii) to analyze the trophic positions of metazooplankton by using the stable isotope signatures of a wide variety of taxa and particulate organic matter from the Iles Eparses and Mayotte.

Consequences of contaminant mixture on the dynamics and functional diversity of bacterioplankton in a southwestern Mediterranean coastal ecosystem.

Contamination of coastal environments is often due to a complex mixture of pollutants, sometimes in trace levels, that may have significant effects on diversity and function of organisms. The aim of this study was to evaluate the short-term dynamics of bacterioplankton exposed to natural and artificial mixtures of contaminants. Bacterial communities from a southwestern Mediterranean ecosystem, lagoon and the bay (offshore) of Bizerte were exposed to i) elutriate from resuspension of contaminated sediment, and ii) an artificial mixture of metals and herbicides mimicking the contamination observed during sediment resuspension.

Taking Advantage of Electric Field Induced Bacterial Aggregation for the Study of Interactions between Bacteria and Macromolecules by Capillary Electrophoresis.

The quantification of interaction stoichiometry and binding constant between bacteria (or other microorganism) and (macro)molecules remains a challenging issue for which only a few adapted methods are available. In this paper, a new methodology was developed for the determination of the interaction stoichiometry and binding constant between bacteria and (macro)molecules. The originality of this work is to take advantage of the bacterial aggregation phenomenon to directly quantify the free ligand concentration in equilibrated bacteria-ligand mixtures using frontal analysis continuous capillary electrophoresis.

Changes of benthic bacteria and meiofauna assemblages during bio-treatments of anthracene-contaminated sediments from Bizerta lagoon (Tunisia).

Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenarios for the bioremediation of anthracene-polluted sediments, namely bioaugmentation, biostimulation, and a combination of both bioaugmentation and biostimulation. In order to investigate the effect of the biotreatments on the benthic biosphere, 16S rRNA gene-based T-RFLP bacterial community structure and the abundance and diversity of the meiofauna were determined throughout the experiment period. Addition of fresh anthracene drastically reduced the benthic bacterial and meiofaunal abundances.

Changes in bacterial community metabolism and composition during the degradation of dissolved organic matter from the jellyfish Aurelia aurita in a Mediterranean coastal lagoon.

Spatial increases and temporal shifts in outbreaks of gelatinous plankton have been observed over the past several decades in many estuarine and coastal ecosystems. The effects of these blooms on marine ecosystem functioning and particularly on the dynamics of the heterotrophic bacteria are still unclear. The response of the bacterial community from a Mediterranean coastal lagoon to the addition of dissolved organic matter (DOM) from the jellyfish Aurelia aurita, corresponding to an enrichment of dissolved organic carbon (DOC) by 1.

Off-site impacts of agricultural composting: role of terrestrially derived organic matter in structuring aquatic microbial communities and their metabolic potential.

While considered as sustainable and low-cost agricultural amendments, the impacts of organic fertilizers on downstream aquatic microbial communities remain poorly documented. We investigated the quantity and quality of the dissolved organic matter leaching from agricultural soil amended with compost, vermicompost or biochar and assessed their effects on lake microbial communities, in terms of viral and bacterial abundances, community structure and metabolic potential. The addition of compost and vermicompost significantly increased the amount of dissolved organic carbon in the leachate compared with soil alone.

Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters.

The effects of grazing pressure and inorganic nutrient availability on the direct carbon transfer from freshly produced phytoplankton exudates to heterotrophic bacteria biomass production were studied in Mediterranean coastal waters. The short-term incorporation of ¹³C (H¹³CO₃) in phytoplankton and bacterial lipid biomarkers was measured as well as the total bacterial carbon production (BP), viral lysis and the microbial community structure under three experimental conditions: (1) High inorganic Nutrient and High Grazing (HN + HG), (2) High inorganic Nutrient and Low Grazing (HN + LG) and (3) under natural in situ conditions with Low inorganic Nutrient and High Grazing (LN + HG) during spring. Under phytoplankton bloom conditions (HN + LG), the bacterial use of freshly produced phytoplankton exudates as a source of carbon, estimated from ¹³C enrichment of bacterial lipids, contributed more than half of the total bacterial production.

The roles of biological interactions and pollutant contamination in shaping microbial benthic community structure.

Biological interactions between metazoans and the microbial community play a major role in structuring food webs in aquatic sediments. Pollutants can also strongly affect the structure of meiofauna and microbial communities. This study aims investigating, in a non-contaminated sediment, the impact of meiofauna on bacteria facing contamination by a mixture of three PAHs (fluoranthene, phenanthrene and pyrene).

Mangrove microbial diversity and the impact of trophic contamination.

Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not.

Microbial community responses to bioremediation treatments for the mitigation of low-dose anthracene in marine coastal sediments of Bizerte lagoon (Tunisia).

Purpose: The main goals of this study were to investigate (1) the behavior of microbial communities in response to low-dose bioavailable anthracene addition in lightly contaminated sediment from Bizerte Lagoon and (2) the effects of bioremediation treatments on microbial biomass, activity, and community structure.

Methods: Sediment microcosms amended with 1 ppm anthracene were incubated in triplicate during 30 days. Biostimulation (addition of nitrogen and phosphorus fertilizer) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation treatments.

Phytoplankton distribution and productivity in a highly turbid, tropical coastal system (Bach Dang Estuary, Vietnam).

Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations.

Use of OmpU porins for attachment and invasion of Crassostrea gigas immune cells by the oyster pathogen Vibrio splendidus.

OmpU porins are increasingly recognized as key determinants of pathogenic host Vibrio interactions. Although mechanisms remain incompletely understood, various species, including the human pathogen Vibrio cholera, require OmpU for host colonization and virulence. We have shown previously that OmpU is essential for virulence in the oyster pathogen Vibrio splendidus LGP32.

Survival study of enterotoxigenic Escherichia colistrain in seawater and wastewater microcosms.

In order to survey osmotic and oligotrophic stress consequence on pathogenic enterobacteria discharged in marine areas, we examined enterotoxigenic Escherichia coli (ETEC) and a reference (Ecoli O126:B16) strains during their survival (47 days) in wastewater microcosms, submerged in natural seawater and maintained in laboratory conditions. The results revealed that the survival time for the two strains was prolonged when bacterial cells were previously incubated in wastewater, with less cellular membrane damage. In addition, the wild clinical E.