Influence of nutrient enrichment on colonisation and photosynthetic parameters of hard substrate marine microphytobenthos.

This study aimed to assess the influence of nutrient enrichment on the development of microalgal biofilm on concrete and PVC cubes. Three mesocosms were utilized to create a nutrient gradient over a period of 28 days. Various parameters including biomass, photosynthetic activity, microtopography, and extracellular polymeric substances (EPS) were measured. Imaging PAM techniques were employed to obtain surface-wide data. Results revealed that nutrient availability had no significant impact on Chl a biomass and the maximum quantum efficiency of PSII (Fv/Fm). The photosynthetic capacity and efficiency were minimally affected by nutrient availability. Interestingly, the relationship between microphytobenthic (MPB) biomass and photosynthesis and surface rugosity exhibited distinct patterns. Negative reliefs showed a strong correlation with Fv/Fm, while no clear pattern emerged for biomass on rough concrete structures. Overall, our findings demonstrate that under conditions of heightened eutrophication, biofilm photosynthesis thrives in the fissures and crevasses of colonized structures regardless of nutrient levels. This investigation provides valuable insights into the interplay between nutrient availability and surface rugosity.

First isolation of Francisella halioticida strains from blue mussel (Mytilus edulis) in Normandy, France.

Mass mortality events affecting the blue mussels Mytilus edulis have been observed in France since 2014. The DNA of the bacterium Francisella halioticida, reported as pathogen of giant abalone (Haliotis gigantea) and Yesso scallop (Mizuhopecten yessoensis) has been detected recently in mussels from areas suffering mortalities. Isolation of this bacterium was attempted from individuals collected during mortality events. Identification was performed by 16S rRNA gene sequencing, real-time specific PCR and MALDI-ToF using spectra produced from the strain 8472-13A isolated from diseased Yesso scallop in Canada. Five isolates were identified as F. halioticida by real-time specific PCR and 16S rRNA sequencing. MALDI-ToF allowed the direct identification of four isolates (FR22a,b,c,d) which had 100% identity on the 16S rRNA gene with the known strains. On the other hand, one isolate (FR21) was not recognized by MALDI-ToF and had 99.9% identity on the 16S rRNA gene. The FR22 isolates showed difficult growth and required media optimization, which was not the case with the FR21 isolate. For these reasons, it was hypothesized that two type strains are present on French coasts, named FR21 and FR22. The FR21 isolate was selected for phenotypic analysis (growth curve, biochemical characteristics, electron microscopy), phylogenetic analysis and an experimental challenge. This isolate showed distinct differences compared to published F. halioticida strains, both at phenotypic and genotypic levels. Experimental infections of adult mussels led to 36% mortalities in 23 days following intramuscular injection with 3 × 107 CFU while a lower dose (3 × 103 CFU) did not lead to significant mortalities. In the context of this study, the strain FR21 was not virulent towards adult mussels.

Molecular approaches to uncover phage-lactic acid bacteria interactions in a model community simulating fermented beverages.

Food microbial diversity and fluxes during the fermentation processes are well studied whereas phages-bacteria interactions are still poorly described in the literature. This is especially true in fermented beverages, and especially in cider, which is an alcoholic fermented apple beverage. The transcriptomic and proteomic responses of the lactic acid bacterium (LAB) Liquorilactobacillus mali UCMA 16447 to a lytic infection by phage UCMA 21115, both isolated from cider, were investigated, in order to get a better understanding of phages-bacteria interactions in such fermented beverage. During phage infection, 122 and 215 genes were differentially expressed in L. mali UCMA 16447 strain at T15 and T60 respectively, when compared to the uninfected condition. The same trends were confirmed by the proteomic study, with a total of 28 differentially expressed proteins found at T60. Overall, genes encoding cellular functions, such as carbohydrate metabolism, translation, and signal transduction, were downregulated, while genes involved in nucleotide metabolism and in the control of DNA integrity were upregulated in response to phage infection. This work also highlighted that phage infection repressed many genes involved in bacterial cell motility, and affected glycolysis.

Pseudomonas crudilactis sp. nov., isolated from raw milk in France.

Strains belonging to the Pseudomonas genus have been isolated worldwide from various biotic (humans, animals and plant tissues) and abiotic (food, soil, water and air) environments. Raw milk provides a favorable environment for the growth of a broad spectrum of microorganisms, including Pseudomonas. Here we present the description of Pseudomonas sp. UCMA 17988 isolated from raw milk, which was previously reported to produce new antimicrobial lipopeptides. MultiLocus Sequence Analysis of four housekeeping genes (16S rRNA, gyrB, rpoD and rpoB), whole genome sequence comparison (orthoANI value, original ANI value and dDDH value), microscopy, FAME analysis, and biochemical tests were performed. Digital DNA-DNA hybridization and average nucleotide identity values between strain UCMA 17988 and its closest relatives, P. helmanticensis CECT 8548T (46.9%, 92.07%) and P. baetica CECT 7720T (26.8%, 88.50%), rate well below the designed threshold for assigning prokaryotic strains to the same species. In conclusion, strain UCMA 17988 belongs to a novel species, for which the name Pseudomonas crudilactis sp. nov (type strain UCMA 17988T = DSM 109949T = LMG 31804T) is proposed.

Influence of infrastructure material composition and microtopography on marine biofilm growth and photobiology.

The impact of concrete composition and roughness on the formation of microalgal biofilms and their photobiology were studied on marine infrastructures presenting four different compositions combined with two degrees of roughness (rough and smooth). The structures were first inoculated with a natural microphytobenthic biofilm and immersed in sterilised seawater with a controlled photoperiod for six days. Photosynthetic activity was assessed with an imaging PAM-(Pulse Amplitude Modulated) fluorometer and microtopography was monitored in parallel with a 3-D camera. The results indicated that roughness had an impact on the biofilm biomass, its physiological status and its photosynthetic efficiency and capacity. The assessment of surface roughness indicated that negative reliefs were preferably colonised by MPB (microphytobenthic) cells with better photosynthetic performances. Moreover, MPB biofilms showed better photoacclimation in these microhabitats than on the positive and smooth reliefs. This study confirms the importance of microhabitat for biofilm formation and their photobiology.

Unexpected Cell Wall Alteration-Mediated Bactericidal Activity of the Antifungal Caspofungin against Vancomycin-Resistant Enterococcus faecium.

Enterococcus faecium has become a major opportunistic pathogen with the emergence of vancomycin-resistant enterococci (VRE). As part of the gut microbiota, they have to cope with numerous stresses, including effects of antibiotics and other xenobiotics, especially in patients hospitalized in intensive care units (ICUs) who receive many medications. The aim of this study was to investigate the impact of the most frequently prescribed xenobiotics for ICU patients on fitness, pathogenicity, and antimicrobial resistance of the vanB-positive E. faecium Aus0004 reference strain. Several phenotypic analyses were carried out, and we observed that caspofungin, an antifungal agent belonging to the family of echinocandins, had an important effect on E. faecium growth in vitro We confirmed this effect by electron microscopy and peptidoglycan analysis and showed that, even at a subinhibitory concentration (1/4× MIC, 8 mg/liter), caspofungin had an impact on cell wall organization, especially with respect to the abundance of some muropeptide precursors. By transcriptome sequencing (RNA-seq), it was also shown that around 20% of the transcriptome was altered in the presence of caspofungin, with 321 and 259 significantly upregulated and downregulated genes, respectively. Since the fungal target of caspofungin (i.e., ß-1,3-glucan synthase) was absent in bacteria, the mechanistic pathway of caspofungin activity was investigated. The repression of genes involved in the metabolism of pyruvate seemed to have a drastic impact on bacterial cell viability, while a decrease of glycerol metabolism could explain the conformational modifications of peptidoglycan. This is the first report of caspofungin antibacterial activity against E. faecium, highlighting the potential impact of nonantibiotic xenobiotics against bacterial pathogens.

Phenotypic and proteomic approaches of the response to iron-limited condition in Staphylococcus lugdunensis.

BACKGROUND: Staphylococcus lugdunensis is a coagulase-negative Staphylococcus part of the commensal skin flora but emerge as an important opportunistic pathogen. Because iron limitation is a crucial stress during infectious process, we performed phenotypic study and compared proteomic profiles of this species incubated in absence and in presence of the iron chelator 2,2'-dipyridyl (DIP). RESULTS: No modification of cell morphology nor cell wall thickness were observed in presence of DIP. However iron-limitation condition promoted biofilm formation and reduced the ability to cope with oxidative stress (1 mM H2O2). In addition, S. lugdunensis N920143 cultured with DIP was significantly less virulent in the larvae of Galleria mellonella model of infection than that grown under standard conditions. We verified that these phenotypes were due to an iron limitation by complementation experiments with FeSO4. By mass spectrometry after trypsin digestion, we characterized the first iron-limitation stress proteome in S. lugdunensis. Among 1426 proteins identified, 349 polypeptides were differentially expressed. 222 were more and 127 less abundant in S. lugdunensis incubated in iron-limitation condition, and by RT-qPCR, some of the corresponding genes have been shown to be transcriptionally regulated. Our data revealed that proteins involved in iron metabolism and carriers were over-expressed, as well as several ABC transporters and polypeptides linked to cell wall metabolism. Conversely, enzymes playing a role in the oxidative stress response (especially catalase) were repressed. CONCLUSIONS: This phenotypic and global proteomic study allowed characterization of the response of S. lugdunensis to iron-limitation. We showed that iron-limitation promoted biofilm formation, but decrease the oxidative stress resistance that may, at least in part, explained the reduced virulence of S. lugdunensis observed under low iron condition.

Morphological and molecular criteria allow the identification of putative germ stem cells in a lophotrochozoan, the Pacific oyster Crassostrea gigas.

While our knowledge of bivalve gametogenesis recently progressed, data on early stages of gametogenesis remain to be developed, especially when dealing with germinal stem cells (GSC) and their niche in these organisms. Here, we wish to develop a strategy to identify putative GSC in Pacific oyster Crassostrea gigas based on morphological criteria combined with vasa marker expression. A histological quantitative approach, based on stereology, allowed us to identify two types of early germ cells in the germinal epithelium, one presenting round nuclei and the other irregular ones. Both early germ cell types present slightly condensed chromatin in nucleus, are vasa-positive and the Oyvlg (oyster vasa-like gene) expression in these cells is recorded throughout the whole gametogenesis process. The microenvironment of an early germ cell in oyster includes an associated somatic cell presenting an immunolabeling for BMP2/4 and a close myoid cell. In agreement with the GSC characteristics in other species, we postulate that putative germ stem cells in C. gigas correspond to the early germ cell type with irregular nucleus shape; those early germ cells with a round nucleus may consist in progenitors.

A role for RASSF1A in tunneling nanotube formation between cells through GEFH1/Rab11 pathway control.

BACKGROUND: By allowing intercellular communication between cells, tunneling nanotubes (TNTs) could play critical role in cancer progression. If TNT formation is known to require cytoskeleton remodeling, key mechanism controlling their formation remains poorly understood. METHODS: The cells of human bronchial (HBEC-3, A549) or mesothelial (H2452, H28) lines are transfected with different siRNAs (inactive, anti-RASSF1A, anti-GEFH1 and / or anti-Rab11). At 48 h post-transfection, i) the number and length of the nanotubes per cell are quantified, ii) the organelles, previously labeled with specific tracers, exchanged via these structures are monitored in real time between cells cultured in 2D or 3D and in normoxia, hypoxia or in serum deprivation condition. RESULTS: We report that RASSF1A, a key-regulator of cytoskeleton encoded by a tumor-suppressor gene on 3p chromosome, is involved in TNTs formation in bronchial and pleural cells since controlling proper activity of RhoB guanine nucleotide exchange factor, GEF-H1. Indeed, the GEF-H1 inactivation induced by RASSF1A silencing, leads to Rab11 accumulation and subsequent exosome releasing, which in turn contribute to TNTs formation. Finally, we provide evidence involving TNT formation in bronchial carcinogenesis, by reporting that hypoxia or nutriment privation, two almost universal conditions in human cancers, fail to prevent TNTs induced by the oncogenic RASSF1A loss of expression. CONCLUSIONS: This finding suggests for the first time that loss of RASSF1A expression could be a potential biomarker for TNTs formation, such TNTs facilitating intercellular communication favoring multistep progression of bronchial epithelial cells toward overt malignancy.

Identification of a moronecidin-like antimicrobial peptide in the venomous fish Pterois volitans: Functional and structural study of pteroicidin-α.

The present study characterizes for the first time an antimicrobial peptide in lionfish (Pterois volitans), a venomous fish. Using a peptidomic approach, we identified a mature piscidin in lionfish and called it pteroicidin-α. We detected an amidated form (pteroicidin-α- CONH2) and a non-amidated form (pteroicidin-α-COOH), and then performed their functional and structural study. Interestingly, the two peptides displayed different antibacterial and hemolytic activity levels. Pteroicidin-α-CONH2 was bactericidal on human pathogens like Staphylococcus aureus or Escherichia coli, as well as on the fish pathogen Aeromonas salmonicida, while pteroicidin-α-COOH only inhibited their growth. Furthermore, the two peptides induced hemolysis of red blood cells from different vertebrates, namely humans, sea bass and lesser-spotted dogfish. Hemolysis occurred with low concentrations of pteroicidin-α-CONH2, indicating greater toxicity of the amidated form. Circular dichroism analysis showed that both peptides adopted a helical conformation, yet with a greater α-helix content in pteroicidin-α-CONH2. Overall, these results suggest that amidation strongly influences pteroicidin-α by modifying its structure and its physico-chemical characteristics and by increasing its hemolytic activity.

Disruption of a miR-29 binding site leading to COL4A1 upregulation causes pontine autosomal dominant microangiopathy with leukoencephalopathy.

OBJECTIVE: Cerebral small vessel disease (cSVD) is a heterogeneous group of disorders. Screening of known cSVD genes identifies the causative mutation in <15% of familial cSVD cases. We sought to identify novel causes of cSVD. METHODS: We used linkage analysis and exome sequencing to identify the causal mutation in a French cSVD family. The identified candidate gene was then screened in 202 cSVD unrelated probands, including 1 proband from the first reported pontine autosomal dominant microangiopathy with leukoencephalopathy (PADMAL) family. Sanger sequencing was used to confirm variants in all mutated probands and analyze their segregation in probands' relatives. Mutation consequences were assessed with luciferase reporter assays and real-time quantitative polymerase chain reaction (RT-qPCR). RESULTS: A candidate heterozygous variant located in a predicted miR-29 microRNA binding site, within the 3' untranslated region of COL4A1, was identified in the large French cSVD family. Five additional unrelated probands, including the PADMAL proband, harbored heterozygous variants in this microRNA binding site. Variants cosegregated with the affected phenotype, and cumulative logarithm of odds score reached 6.03, establishing linkage to this locus. A highly significant difference was observed when comparing the number of variants within this binding site in cases and controls (p = 1.77 × 10E-12). RT-qPCR analyses of patients' primary fibroblasts and luciferase reporter assays strongly favor an upregulation of COL4A1 mediated by disruption of miR-29 binding to its target site. Magnetic resonance imaging features were characterized by the presence of multiple pontine infarcts in all symptomatic mutation carriers. INTERPRETATION: Mutations upregulating COL4A1 expression lead to PADMAL, a severe early onset ischemic cSVD, distinct from the various phenotypes associated with COL4A1 missense glycine mutations. Ann Neurol 2016;80:741-753.

Sequential steps of daptomycin resistance in Enterococcus faecium and reversion to hypersusceptibility through IS-mediated inactivation of the liaFSR operon.

OBJECTIVES: To improve understanding of mechanisms of daptomycin resistance and to dissect the genetic basis of reversion to daptomycin hypersusceptibility in Enterococcus faecium. METHODS: Daptomycin-resistant mutants (Mut4, Mut8, Mut16, Mut32, Mut64 and Mut128 with MICs from 4 to 128 mg/L) were obtained in vitro from E. faecium strain Aus0004 (MIC at 2 mg/L). The entire genome sequences of Mut64 and Mut128 were determined as well as those of liaFSR and cls genes for other mutants and corresponding revertants (named Rev4 to Rev128). The study of daptomycin resistance stability was performed without any selective pressure. The expression of liaF, liaS and liaR genes was quantified by quantitative RT-PCR. RESULTS: By comparative genomic analysis, substitutions Asn13Ser in cls and Gly92Asp in liaS were identified in Mut64 and Mut128. Only the liaS mutation was found in Mut16 and Mut32 while Mut4 and Mut8 were devoid of any mutation. After 15 days, all mutants except Mut4 reverted to daptomycin hypersusceptibility (MICs from 0.12 to 0.25 mg/L). In all revertants (except Rev4 and Rev8), an IS was found in the liaFSR operon with a dramatic decrease of its expression: IS66 in the promoter region of liaF (Rev16 and Rev64), IS30 in liaR (Rev32) and IS982 in liaF (Rev128). CONCLUSIONS: We demonstrated the stepwise and sequential acquisition of mutations in liaS and in cls leading to daptomycin resistance in E. faecium, and the instability of daptomycin resistance as well as the role of liaFSR inactivation in reversion to daptomycin hypersusceptibility.

Implication of the estrogen receptors GPER, ESR1, ESR2 in post-testicular maturations of equine spermatozoa.

Estrogen receptors ESR1, ESR2 and GPER are present on mature ejaculated horse spermatozoa, suggesting these cells as putative targets for estrogens. Indeed, spermatozoa are exposed to high level of estrogens during the transit in the male and female genital tracts but their roles are not investigated. So, we evaluated in vitro the role of 17ß-estradiol during post-testicular maturations: regulation of motility, capacitation and acrosome reaction. Moreover according to the pseudo-seasonal breeder status of the stallion, we analyzed the putative seasonal variations in the presence of ESRs in spermatozoa. We showed that ESRs are more present on stallion sperm during the breeding season. We showed that capacitation and acrosome reaction are independent of estradiol action in horse. Estradiol can weakly modulate the motility and this effect is strictly associated with GPER and not with ESR1 and ESR2. The subcellular localization of GPER in the neck on stallion sperm is coherent with this effect. It seems that estrogens are not major regulators of sperm maturations associated to mare genital tract, so they could act during the epididymal maturations.

Hemocyte morphology and phagocytic activity in the common cuttlefish (Sepia officinalis).

Little is known about the immune system of cephalopods, in spite of their many highly derived characters within the molluscan clade, including a vertebrate-like high-pressure closed circulatory system. Further the economic importance of cephalopod fisheries, potential for aquaculture, and use as ecotoxicology models demand a thorough understanding of their immune system. In this study, we present a comprehensive characterization of hemocytes in the common cuttlefish Sepia officinalis. Cytological stainings, electron microscopy- and flow cytometry-observations highlight a single granulocyte population with various densities of eosinophilic granules and unstained vesicles. These hemocytes contain acid phosphatase-, lysozyme- and proPO system enzymes, and have high activity in bead phagocytosis assays. Interestingly, bead pre-incubation in plasma results in time-dependent aggregation perhaps resulting from hemocyanin-coating, and decrease in phagocytosis. This study provides the basis for understanding hemocyte-mediated immunity in the common cuttlefish, and essential background for future studies on cephalopod immunity.

Stallion spermatozoa: putative target of estrogens; presence of the estrogen receptors ESR1, ESR2 and identification of the estrogen-membrane receptor GPER.

Among mammals, the stallion produces the largest amount of testicular estrogens. These steroid hormones are produced mainly by Leydig and Sertoli cells in the testis and also in the epididymis. Their role in horse testicular physiology and their ability to act on spermatozoa are still unknown. In order to determine if spermatozoa are targets for estrogens, the presence of estrogen receptors in mature ejaculated spermatozoa has been investigated. The presence of a single isoform of ESR1 (66kDa) and ESR2 (61kDa) was found by Western-blot analysis in samples from seven stallions. Confocal analysis mainly showed a flagellar localization for both receptors. Immuno-TEM experiments revealed that they are mostly located near the membranes, which are classically associated with rapid, non-genomic, effects. Moreover, we evidenced the expression of the seven transmembrane estradiol binding receptor GPER in colt testis. The protein was also localized at the connecting piece in mature spermatozoa. In conclusion, our results suggest that horse spermatozoa are a target for estrogens, which could act on several receptors either during the epididymal transit and/or in the female genital tract.

Study of lysozyme resistance in Rhodococcus equi.

Lysozyme is an important and widespread component of the innate immune response that constitutes the first line of defense against bacterial pathogens. The bactericidal effect of this enzyme relies on its capacity to hydrolyze the bacterial cell wall and also on a nonenzymatic mechanism involving its cationic antimicrobial peptide (CAMP) properties, which leads to membrane permeabilization. In this paper, we report our findings on the lysozyme resistance ability of Rhodococcus equi, a pulmonary pathogen of young foals and, more recently, of immunocompromised patients, whose pathogenic capacity is conferred by a large virulence plasmid. Our results show that (i) R. equi can be considered to be moderately resistant to lysozyme, (ii) the activity of lysozyme largely depends on its muramidase action rather than on its CAMP activity, and (iii) the virulence plasmid confers part of its lysozyme resistance capacity to R. equi. This study is the first one to demonstrate the influence of the virulence plasmid on the stress resistance capacity of R. equi and improves our understanding of the mechanisms enabling R. equi to resist the host defenses.

Generation and characterization of two new monoclonal antibodies produced by immunizing mice with plant fructans: New tools for immunolocalization of ß-(2 → 1) and ß-(2 → 6) fructans.

Fructans are water-soluble polymers of fructose in which fructose units are linked by ß-(2 â†’ 1) and/or ß-(2 â†’ 6) linkages. In plants, they are synthesized in the vacuole but have also been reported in the apoplastic sap under abiotic stress suggesting that they are involved in plasmalemma protection and in plant-microbial interactions. However, the lack of fructan-specific antibodies currently prevents further study of their role and the associated mechanisms of action, which could be elucidated thanks to their immunolocalization. We report the production of two monoclonal antibodies (named BTM9H2 and BTM15A6) using mice immunization with antigenic compounds prepared from a mixture of plant inulins and levans conjugated to serum albumin. Their specificity towards fructans with ß-(2 â†’ 1) and/or ß-(2 â†’ 6) linkage has been demonstrated by immuno-dot blot tests on a wide range of carbohydrates. The two mAbs were used for immunocytolocalization of fructans by epifluorescence microscopy in various plant species. Fructan epitopes were specifically detected in fructan-accumulating plants, inside cells as well as on the surface of root tips, confirming both extracellular and intracellular localizations. The two mAbs provide new tools to identify the mechanism of extracellular fructan secretion and explore the roles of fructans in stress resistance and plant-microorganism interactions.

MRI-based microthrombi detection in stroke with polydopamine iron oxide.

In acute ischemic stroke, even when successful recanalization is obtained, downstream microcirculation may still be obstructed by microvascular thrombosis, which is associated with compromised brain reperfusion and cognitive decline. Identifying these microthrombi through non-invasive methods remains challenging. We developed the PHySIOMIC (Polydopamine Hybridized Self-assembled Iron Oxide Mussel Inspired Clusters), a MRI-based contrast agent that unmasks these microthrombi. In a mouse model of thromboembolic ischemic stroke, our findings demonstrate that the PHySIOMIC generate a distinct hypointense signal on T2*-weighted MRI in the presence of microthrombi, that correlates with the lesion areas observed 24 hours post-stroke. Our microfluidic studies reveal the role of fibrinogen in the protein corona for the thrombosis targeting properties. Finally, we observe the biodegradation and biocompatibility of these particles. This work demonstrates that the PHySIOMIC particles offer an innovative and valuable tool for non-invasive in vivo diagnosis and monitoring of microthrombi, using MRI during ischemic stroke.

Cold-shock RNA-binding protein CspR is also exposed to the surface of Enterococcus faecalis.

CspR has been characterized recently as a cold-shock RNA-binding protein in Enterococcus faecalis, a natural member of the gastro-intestinal tract capable of switching from a commensal relationship with the host to an important nosocomial pathogen. In addition to its involvement in the cold-shock response, CspR also plays a role in the long-term survival and virulence of E. faecalis. In the present study, we demonstrated that anti-CspR immune rabbit serum protected larvae of Galleria mellonella against a lethal challenge of the WT strain. These results suggested that CspR might have a surface location. This hypothesis was verified by Western blot that showed detection of CspR in the total as well as in the surface protein fraction. In addition, identification of surface polypeptides by proteolytic shaving of intact bacterial cells followed by liquid chromatography-MS-MS revealed that cold-shock proteins (EF1367, EF2939 and CspR) were present on the cell surface. Lastly, anti-CspR immune rabbit serum was used for immunolabelling and detected with colloidal gold-labelled goat anti-rabbit IgG in order to determine the immunolocalization of CspR on E. faecalis WT strain. Electron microscopy images confirmed that the cold-shock protein RNA-binding protein CspR was present in both cytoplasmic and surface parts of the cell. These data strongly suggest that CspR, in addition to being located intracellularly, is also present in the extracellular protein fraction of the cells and has important functions in the infection process of Galleria larvae.

Aluminium-based galvanic anode impacts the photosynthesis of microphytobenthos and supports the bioaccumulation of metals released.

Very few studies have looked at the potential biological effects of degradation products of galvanic anodes particularly on primary producers which are central to food webs in marine ecosystems. The galvanic anode cathodic protection system (GACP) is widely used to protect submerged metallic structures from corrosion. Aluminium (Al) and zinc (Zn) are the main constituents of galvanic anodes and are therefore released in the marine environment by oxidation process to form ions or oxy-hydroxides. The main objective of our study was to evaluate the effects of the metals released from an aluminium-based galvanic anode on microphytobenthos performance in term of biofilm growing through the analysis of photosynthetic parameters, the determination of chlorophyll and extracellular polymeric substances (EPS). The bioaccumulation of Al and Zn were measured in the microphytobenthic compartment collected at the surface of polyvinyl chloride (PVC) plates exposed during 13 days to seawaters enriched in different concentrations of metals released from dissolution of one anode. Determination of bioconcentration factors confirmed that the microphytobenthos has incorporated Al. A significative effect was observed on the Chl a concentration for the higher tested concentration ([Al] = 210.1 ± 60.2 µg L - 1; [Zn] = 20.2 ± 1.4 µg L - 1). The seawater exposed to the anode affected the MPB productivity (ETRIImax) with consequences on acclimatation light (Ek), absorption cross section of PSII (σPII), Fv/Fm and NPQ. Regarding the EPS production, the anode degradation presented an impact on high and low molecular weight of both carbohydrates and protein fractions of microphytobenthos suggesting that EPS play an essential role in sequestering metal contaminants to maintain the integrity of the biological membranes and the functionality of the cellular organelles. The accumulation of Al released by GACP in microphytobenthos cells could lead to physiologic problems in photosynthetic organisms.