Natural Biofilms Research Articles

Meta-analysis of glyphosate contamination in surface waters and dissipation by biofilms

One consequence of the intensive use of glyphosate is the contamination of rivers by the active substance and its metabolites aminomethyl phosphonic acid (AMPA) and sarcosine, inducing river eutrophication. Biofilms are the predominant lifestyle for microorganisms in rivers, providing pivotal roles in ecosystem functioning and pollutant removal. The persistence of glyphosate in these ecosystems is suspected to be mostly influenced by microbial biodegradation processes.The present study aimed to investigate the tripartite relationship among biofilms, phosphorus and glyphosate in rivers. The first part consists of a co-occurrence analysis among glyphosate, AMPA and phosphorus using an extensive dataset of measurements (n = 56,198) from French surface waters between 2013 and 2017. The second part investigated the capacity of natural river biofilms to dissipate glyphosate, depending on phosphorus availability and the exposure history of the biofilm, in a microcosm study.A strong co-occurrence among glyphosate, AMPA and phosphorus was found in surface waters. More than two-thirds of samples contained phosphorous with glyphosate, AMPA or both compounds. Seasonal fluctuations in glyphosate, AMPA and phosphorus concentrations were correlated, peaking in spring/summer shortly after pesticide spreading. Laboratory experiments revealed that natural river biofilms can degrade glyphosate. However, phosphorus availability negatively influenced the biodegradation of glyphosate and induced the accumulation of AMPA in water. An increase in alkaline phosphatase activity and phosphorus uptake was observed in glyphosate-degrading biofilms, evidencing the tight link between phosphorus limitation and glyphosate degradation by biofilms.The results of the present study show that phosphorus not only is a key driver of river eutrophication but also can reduce complete glyphosate degradation by biofilms and favour the accumulation of AMPA in river water. The predominant role of biofilms and the trophic status of rivers must therefore be considered in order to better assess the fate and persistence of glyphosate.

Advanced characterization of natural biofilm on nanofiber scaffold

Nanofiber scaffolds provide numerous advantages over common carriers engineered for microorganisms. The most important advantage is an increased speed of primary surface colonization (up to four times faster), which shortens the time required for the areal biofilm formation and optimum performance of attached microorganisms (higher efficiency of biological activity of up to twice as fast). Image analysis predicts early formation of biofilm even in beginning stages; analysis of biofilm reveals the different structures of bacterial colonies on both scaffolds (higher porosity, size, and number of bacterial colonies on nanofiber's surface). The image analysis correlates well with determinations of dry matter (linear correlation of 0.96) and proteins (linear correlation of 0.89).

Dynamics of Bacterial Communities Mediating the Treatment of an As-Rich Acid Mine Drainage in a Field Pilot.

Passive treatment based on iron biological oxidation is a promising strategy for Arsenic (As)-rich acid mine drainage (AMD) remediation. In the present study, we characterized by 16S rRNA metabarcoding the bacterial diversity in a field-pilot bioreactor treating extremely As-rich AMD in situ, over a 6 months monitoring period. Inside the bioreactor, the bacterial communities responsible for iron and arsenic removal formed a biofilm (“biogenic precipitate”) whose composition varied in time and space. These communities evolved from a structure at first similar to the one of the feed water used as an inoculum to a structure quite similar to the natural biofilm developing in situ in the AMD. Over the monitoring period, iron-oxidizing bacteria always largely dominated the biogenic precipitate, with distinct populations (Gallionella, Ferrovum, Leptospirillum, Acidithiobacillus, Ferritrophicum), whose relative proportions extensively varied among time and space. A spatial structuring was observed inside the trays (arranged in series) composing the bioreactor. This spatial dynamic could be linked to the variation of the physico-chemistry of the AMD water between the raw water entering and the treated water exiting the pilot. According to redundancy analysis (RDA), the following parameters exerted a control on the bacterial communities potentially involved in the water treatment process: dissolved oxygen, temperature, pH, dissolved sulfates, arsenic and Fe(II) concentrations and redox potential. Appreciable arsenite oxidation occurring in the bioreactor could be linked to the stable presence of two distinct monophylogenetic groups of Thiomonas related bacteria. The ubiquity and the physiological diversity of the bacteria identified, as well as the presence of bacteria of biotechnological relevance, suggested that this treatment system could be applied to the treatment of other AMD.

Hydrodynamics Alter the Tolerance of Autotrophic Biofilm Communities Toward Herbicides.

Multiple stressors pose potential risk to aquatic ecosystems and are the main reasons for failing ecological quality standards. However, mechanisms how multiple stressors act on aquatic community structure and functioning are poorly understood. This is especially true for two important stressors types, hydrodynamic alterations and toxicants. Here we perform a mesocosm experiment in hydraulic flumes connected as a bypass to a natural stream to test the interactive effects of both factors on natural (inoculated from streams water) biofilms. Biofilms, i.e., the community of autotrophic and heterotrophic microorganisms and their extracellular polymeric substances (EPS) in association with substratum, are key players in stream functioning. We hypothesized (i) that the tolerance of biofilms toward toxicants (the herbicide Prometryn) decreases with increasing hydraulic stress. As EPS is known as an absorber of chemicals, we hypothesize (ii) that the EPS to cell ratio correlates with both hydraulic stress and herbicide tolerance. Tolerance values were derived from concentration-response assays. Both, the herbicide tolerance and the biovolume of the EPS significantly correlated with the turbulent kinetic energy (TKE), while the diversity of diatoms (the dominant group within the stream biofilms) increased with flow velocity. This indicates that the positive effect of TKE on community tolerance was mediated by turbulence-induced changes in the EPS biovolume. This conclusion was supported by a second experiment, showing decreasing effects of the herbicide to a diatom biofilm (Nitzschia palea) with increasing content of artificial EPS. We conclude that increasing hydrodynamic forces in streams result in an increasing tolerance of microbial communities toward chemical pollution by changes in EPS-mediated bioavailability of toxicants.

Sorption removal of phthalate esters and bisphenols to biofilms from urban river: From macroscopic to microcosmic investigation

River biofilms play fundamental roles in shaping the architecture of aquatic systems. Sorption to biofilms was thought to be a crucial mechanism controlling the fate and transport of trace emerging contaminants. This study focused on the role of in situ colonized river biofilms in the early fate of phthalate esters (PAEs) and bisphenols (BPs) at trace concentrations in a representative urban river. PAEs and BPs were readily sorbed to biofilms with uptakes of 38.2–162.5 μg/g for PAEs and 1787.7–4425.6 μg/g for BPs, respectively. The total mass and characteristics of the colonized biofilms varied in response to seasons and water qualities. The biofilm colonized in the downstream of a wastewater treatment plant exhibited the highest sorption capacity among the tested sites, possibly attributed to the higher organic contents of biofilms owing to the elevated availability of nutrients. Correlation analysis indicates that certain water qualities, e.g., TN and NH3N, and biofilm properties, e.g., organic and polysaccharide fractions could be selected to predict the sorption capacities of river biofilms. Hydrophobic partitioning into organic matter appears to be the dominant sorption mechanism and biofilm polysaccharides were probably responsible for the adhesion of tested compounds. The contaminant partitioning into biofilm and sediment at mass/volume ratios typical for small rivers suggests that the biofilm could serve as an important sorbing matrix for the trace organic contaminants as compared to the sediments. Our work yields new insights into the early uptake and accumulation of trace plasticizers by natural biofilms, which is of significance in understanding the subsequent transport of trace organic contaminants in fluvial systems.

Secondary bioreceptivity of granite: effect of salt weathering on subaerial biofilm growth

Salt crystallisation is a very common and powerful weathering agent that can modify the petrophysical properties of building stone such as granite. In addition, the weathering can affect the susceptibility of the stone to biological colonisation. The aims of the present study were to examine the properties of a granite weathered by sodium chloride crystallisation and to evaluate the effects of the weathering on the secondary bioreceptivity of the stone to subaerial phototrophic biofilms. For this purpose, granite samples were subjected to a laboratory-based accelerated salt weathering test, and changes in weight, open porosity, bulk density, capillary water content, abrasion pH and surface roughness of the samples were determined. Samples of both weathered and non-weathered granite were then inoculated with a multi-species phototrophic culture derived from a natural subaerial biofilm and incubated under standardised laboratory conditions for 3 months. The weight loss produced by the weathering process was consistent with significant changes in abrasion pH and surface roughness. The bioreceptivity of the stone was also altered. According to the bioreceptivity index, the granite under study was characterised by ‘mild primary bioreceptivity’, but ‘high secondary bioreceptivity’ after the salt weathering process. Study of the secondary bioreceptivity of stone materials can provide very useful information about response to weathering effects, and the findings can be used to improve the selection of materials for building purposes.

Magnet-assisted rapid and controllable construction of an electroactive biofilm for microbial current generation

Artificial electroactive biofilms have been developed as potential alternative to natural biofilms because the fabrication of them is simple, rapid, standardized and controllable. However, the construction of artificial electroactive biofilms usually involves cell dry process or the use of binding agents, which inevitably decreases the viability of the entrapped cells. Herein, a fast and convenient bacterial immobilization method is proposed as an attempt to construct an artificial electroactive biofilm for microbial energy harvesting, in which bacteria are captured by magnetically active nitrogen-doped Fe3O4/reduced graphene oxide composite and bring onto the electrode by means of external magnetic field. The resulting artificial electroactive biofilm produces higher current than the natural electroactive biofilm in the bioelectrochemical systems. The improved performance of the biofilm captured by nitrogen-doped Fe3O4/reduced graphene oxide can be attributed to its high surface, high affinity for the attachment of Geobacter sulfurreducens, and efficient extracellular electron transfer between microbial biofilm and electrode. Moreover, because of the magnetic activity of the resulting electroactive biofilm, the current produced from the artificial electroactive biofilm is magnetically switchable. This study offers a new approach to rapidly fabricate an artificial electroactive biofilm and provides an opportunity for the fabrication of a magnetically controllable microbial bioelectrochemical system.

Exposure to artificial daylight or UV irradiation (A, B or C) prior to chemical cleaning: an effective combination for removing phototrophs from granite

This study evaluated whether exposing samples of granite colonized by a natural biofilm to artificial daylight or UV-A/B/C irradiation for 48 h enhanced removal of the biofilm with a chemical product previously approved for conservation of monuments by the European Biocide Directive. Rodas granite, which is commonly found in stone-built heritage monuments in Galicia (NW Spain), was naturally colonized by a sub-aerial biofilm. The efficacy of the cleaning method was evaluated relative to uncolonized surfaces and colonized control samples without previous irradiation, treated by dry-brushing or with benzalkonium chloride. The effect of UV irradiation in the combined treatment was evident, as comparable cleaning levels were not reached in the controls. Although the biofilm was not totally removed by any of the treatments, UV-B irradiation followed by benzalkonium chloride was potentially useful for cleaning stone, with results comparable to those achieved by UV-C irradiation, which is known to have germicidal effects.

Experiment on Surface Water Pretreatment by Biological Contact Oxidation Process Filled with Modified Suspending Biochemical Packing

In this paper, surface water of mining cities is pretreated by biological contact oxidation process filled with modified suspending biochemical packing, the characteristics of natural biofilm and the removal of organic pollutants, ammonia nitrogen, total nitrogen and turbidity in surface water were studied. The results show that the structure of mature biofilm is stable and the microbial population appears diversity, and the system has good removal effect on ammonia nitrogen and total nitrogen during the stabilization period, while the removal of organic pollutants and turbidity is slightly worse, the removal effect of the system on organic pollutants, ammonia nitrogen and total nitrogen is better at higher temperatures; on the contrary, the system has a good removal effect on turbidity at lower temperatures.

Plastic Alters Biofilm Quality as Food Resource of the Freshwater GastropodRadix balthica

High amounts of plastic debris enter and accumulate in freshwater systems across the globe. The plastic contamination of benthic habitats in lakes and running waters poses a potential threat to freshwater ecosystems. This study investigates the effects of plastic on two trophic levels of the aquatic food web: primary production, that is, epiplastic biofilm, and primary consumption, that is, a benthic invertebrate grazer. Two plastic types, polymethyl methacrylate (PMMA) and polycarbonate (PC), and glass (control) were used as substrata for natural biofilm establishment. PMMA and PC are, for example, intensively used in the automobile, construction, and electronical industries and in cosmetics (PMMA), CDs, and DVDs (PC). These biofilms were fed to the freshwater gastropod Radix balthica (Linnaeus 1758) in a laboratory-grazing experiment. Biofilm structure and composition were observed using confocal laser scanning microscopy before the grazing experiment. Sublethal effects on R. balthica were observed measuring consumption of biofilm and growth rates. The biofilm composition on PMMA significantly differed compared to PC and glass. The grazing experiments showed limited biofilm consumption and lower growth rates of R. balthica in both plastic treatments. Concluding, plastic in freshwaters has a direct effect on the primary production and an indirect effect on higher trophic levels.

Role of dissolved organic matter from natural biofilms in oxytetracycline photodegradation.

Dissolved organic matter (DOM) is one of the most important factors that influence the photodegradation of antibiotics in the aquatic environment. However, the mechanisms by which DOM produced by natural biofilms (BDOM) influences photodegradation are poorly understood. Here, the influences of BDOM and fulvic acid (FA) as model DOM on the photodegradation of the antibiotic oxytetracycline (OTC) were investigated, and the differences between the characteristics of BDOM and FA were determined by ultraviolet, infrared, and three-dimensional fluorescence spectrum analyses. In addition, an experiment on the scavengers of reactive oxygen species (ROS) was also conducted to explore related mechanisms. The results indicated that the aromaticity degree and molecular weight of BDOM were lower than those of FA. The OTC photodegradation rates increased from 9.7 × 10-2 to 19.9 × 10-2min-1 with increasing BDOM concentration, while they decreased from 8.9 × 10-2 to 5.6 × 10-2min-1 with increasing FA concentration. Excited triplet-state BDOM (3BDOM*) and singlet oxygen (1O2) simultaneously promoted the photodegradation of H2OTC and HOTC-. However, FA inhibited OTC photodegradation through strong light-shielding effects. These results are beneficial for understanding the effects of natural biofilms on the antibiotic photodegradation in the aquatic environment.

Adsorption of Cu2+ and mechanism by natural biofilm.

The biofilm culturing device fixed on the slides was vertically placed in the commonly called small Li Lake of Jiangnan University. The adsorption experiment of Cu2+ was carried out by mature biofilm. Besides, scanning electron microscope (SEM), polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy spectrum (SEM-EDX) were used to analysis the effect of Cu2+ on the morphological structure of biofilm. The result indicated that when the initial concentration of Cu2+ was 5 mg·L-1, the absorption capacity of Cu2+ by unit mass biofilm is the maximum. More extracellular polymeric substances (EPS) were released by biofilm due to the stimulation of Cu2+. EPS was beneficial to the adsorption of Cu2+ by biofilm. After the adsorption of Cu2+, the bacterial diversity index decreased, while there were no significant differences in microbial communities on biofilm. Moreover, the main groups combining Cu2+ were the hydroxyl groups and amide groups in S-EPS and B-EPS. Ion exchange is a mechanism of the adsorption of Cu2+ by EPS.

Gold nanoparticle trophic transfer from natural biofilm to grazer fish

Nanoparticle (NP) trophic transfer is reported as an important exposure route for organisms in aquatic ecosystems. This study focused on gold nanoparticle (AuNP, PEG-coated, 10 nm diameter) transfer using an experimental benthic food chain which included two trophic levels: natural river biofilm and grazer fish Hypostomus plecostomus. AuNP biofilm accumulation was assessed via water AuNP concentrations and total biofilm mass. An extended range of six AuNP concentrations in water (0, 0.0048, 0.048, 0.48, 4.8, and 48 mg Au L−1) was set. A dose-dependent relation between gold concentrations in water and natural river biofilm was observed after a 48-h exposure. This pointed out the high propensity of natural biofilms to accumulate gold. Additionally, total biofilm mass appeared to influence AuNP accumulation at the highest exposure levels. This first step enables the set-up of the transfer experiment in which grazer fish were exposed for 21 days to natural biofilms, previously contaminated by low AuNP concentrations in water (NP0.1: 0.48 and NP1: 4.8 mg Au L−1). Gold was quantified in eight fish organs, and histology was observed. Gold was transferred from biofilms to fish; bioaccumulation was organ- and exposure level-dependent. Interestingly, the brain showed significant gold accumulation at the highest exposure level (NP1). Histological observations indicated distinct inflammatory responses in fish liver, spleen, and muscle. The overall results suggest the potential hazards of subchronic nanoparticle exposure in aquatic organisms.

Consistent and reproducible long-term in vitro growth of health and disease-associated oral subgingival biofilms

BackgroundSeveral in vitro oral biofilm growth systems can reliably construct oral microbiome communities in culture, yet their stability and reproducibility through time has not been well characterized. Long-term in vitro growth of natural biofilms would enable use of these biofilms in both in vitro and in vivo studies that require complex microbial communities with minimal variation over a period of time. Understanding biofilm community dynamics in continuous culture, and whether they maintain distinct signatures of health and disease, is necessary to determine the reliability and applicability of such models to broader studies. To this end, we performed next-generation sequencing on biofilms grown from healthy and disease-site subgingival plaque for 80 days to assess stability and reliability of continuous oral biofilm growth.ResultsBiofilms were grown from subgingival plaque collected from periodontitis-affected sites and healthy individuals for ten eight-day long generations, using hydroxyapatite disks. The bacterial community in each generation was determined using Human Oral Microbe Identification by Next-Generation Sequencing (HOMINGS) technology, and analyzed in QIIME. Profiles were steady through the ten generations, as determined by species abundance and prevalence, Spearman’s correlation coefficient, and Faith’s phylogenetic distance, with slight variation predominantly in low abundance species. Community profiles were distinct between healthy and disease site-derived biofilms as demonstrated by weighted UniFrac distance throughout the ten generations. Differentially abundant species between healthy and disease site-derived biofilms were consistent throughout the generations.ConclusionsHealthy and disease site-derived biofilms can reliably maintain consistent communities through ten generations of in vitro growth. These communities maintain signatures of health and disease and of individual donors despite culture in identical environments. This subgingival oral biofilm growth and perpetuation model may prove useful to studies involving oral infection or cell stimulation, or those measuring microbial interactions, which require the same biofilms over a period of time.

Hot spots of antibiotic tolerant and resistant bacterial subpopulations in natural freshwater biofilm communities due to inevitable urban drainage system overflows

Antibiotic resistant bacteria are a threat to human life. Recently, sewers have been identified as potential reservoirs. The intermittent injection of sewage into adjacent surface waters is inevitable, due to capacity limitations of the urban drainage system. Information regarding the effect to natural freshwater biofilms (NFB) due to the intermittent contaminations are scarce. Therefore, a fundamental screening is necessary. In April, we placed NFB-attachment constructions in a brook upstream and downstream from urban drainage overflow constructions. In meanwhile two sampling campaigns were conducted. The sewage and the brook water were collected to gather information about antibiotic background exposure of ciprofloxacin (CIP), clarithromycin (CLA) and doxycycline (DOX). Six months later we experimentally determined the oxygen uptake rate (OUR) of the NFB-communities after a 24 h lasting exposure with additionally dosed antibiotics. Concentrations of 0.1, 1.0 and 10.0 mg L−1 were selected. CIP, CLA and DOX were individually dosed, and also in mixtures. The mean antibiotic background concentration in sewage was in a range of 575.5–1289.1 ng L−1, which mainly exceeded the concentrations published in literature. The determined mean concentration in the brook was in a range of 4.6–539.0 ng L−1. The first significant inhibition of the OUR with individually dosed antibiotics started mainly at a concentration of 1.0 mg L−1. Antibiotics in a mixture with concentrations of 0.1 and 1.0 mg L−1 were as effective as single dosed antibiotics with a concentration of 10.0 mg L−1. The increased antibiotic tolerance and resistance of NFB-communities downstream of the combined sewer overflow (CSO) structure was a consequence of a severe impact due to urban drainage overflows. Hence, NFB-communities downstream of CSO-constructions are hot spots of antibiotic tolerant and resistant subpopulations and access restrictions should be announced, if an infection risk is present.

Core/Shell Bacterial Cables: A One-Dimensional Platform for Probing Microbial Electron Transfer.

Extracellular electron transfer (EET) from electrochemically active bacteria (EAB) plays a critical role in renewable bioelectricity harvesting through microbial fuel cells (MFC). Comprehensive interpretation and interrogation of EET mechanisms can provide valuable information to enhance MFC performance, which however are still restricted by the intrinsic complexity of natural biofilm. Here, we design core/shell EAB-encapsulating cables as a one-dimensional model system to facilitate EET studies, where the local microenvironments can be rationally controlled to establish structure-function correlations with full biological relevance. In particular, our proof-of-concept studies with Shewanella loihica PV-4 ( S. loihica) encapsulating cables demonstrate the precise modulation of fiber diameters (from 6.9 ± 1.1 to 25.1 ± 2.4 μm) and bacteria interactions, which are found to play important roles in programming the formation of different intercellular structures as revealed by in situ optical and ex situ electron microscopic studies. As-formed bacterial cables exhibit conductivity in the range of 2.5-16.2 mS·cm-1, which is highly dependent on the bacteria density as well as the nature and number of intercellular interconnections. Under electron-acceptor limited conditions, the closely contacted bacteria promote the development of high density self-assembling nanomaterials at cellular interfaces which can be directly translated to the increase of EET efficiency (16.2 mS·cm-1) as compared with isolated, remotely connected bacteria samples (6.4 mS·cm-1). Introducing exceeding concentrations of soluble electron acceptors during cell culture, however, substantially suppresses the formation of cellular interconnections and leads to significantly reduced conductivity (2.5 mS·cm-1). Frequency-dependent measurements further revealthat EET of EAB networks share similar characteristics to electron hopping in conductive polymer matrix, including dominant direct current-conduction in the low frequency region, and alternating current-induced additional electron hopping when the applied frequency is above the critical frequency (105 Hz). The current work represents a strategically new approach for noninvasively probing EET with rationally defined microenvironment and cellular interactions across a wide range of length scales, which is expected to open up new opportunities for tackling the fundamentals and implications of EET.

Microwave-mediated synthesis of zinc oxide nanoparticles: a therapeutic approach against Malassezia species.

A successful protocol was developed to aid in the reduction in dandruff-causing fungi, namely Malassezia globasa and Malassezia furfur. Both the species were isolated from volunteers aged between 20 and 22 suffering from dandruff, cultured ex vivo, and tested against the presence of synthesised zinc oxide nanoparticles (ZnNP). Direct microscopy, scanning electron microscopy (SEM), and biochemical assays specific to Malassezia species were conducted to identify dandruff-causing fungal species. Microwave-mediated synthesis of ZnNP was performed and characterised by UV-vis, X-ray diffraction, and SEM. The nanoparticles were tested against both Malassezia species and proved highly effective in inhibiting these fungi, although M. furfur was more susceptible than M. globosa. An optimum amount of 100 ppm was found to be sufficient to work as an antifungal agent. Synergistic effects of ZnNP with commercial shampoos were tested, and the result showed enhanced antifungal effects. To mimic the natural biofilm formed by these species on human skin, the formation of fungal biofilm was allowed on polystyrene coverslips. ZnNP was effective in eradication biofilm. Since zinc is an essential mineral for all living organism and is considered as biocompatible, the synthesised nanomaterials can be used in the formulation of antidandruff shampoos.

Simulation experiments to elucidate variable fluorescence as a potential proxy for bulk microalgal viability from natural water, sediments and biofilms: Implication in ships ballast water management

The variable fluorescence fluorometry measuring microalgal biomass (initial fluorescence - F0, a chl-a proxy) and photosynthetic efficiency (Fv/Fm) has been suggested as a potential tool in ballast-water assessment. In ballast tank, microalgae can be found in contiguous compartments i.e., in water, sediment, and biofilms. Therefore the utility of F0 and Fv/Fm depends upon proper background corrections, which is straightforward for water samples but not for sediment and biofilms. This study proposes procedures for correcting F0 values from sediment and biofilms. Irrespective of the saturation flash protocol used on any sample types the outcome of the results from viable and non-viable microalgae will remain same. Stress experiments (continuous darkness and biocide treatments) confirm that variable fluorescence (Fv) can be used as a potential proxy for viable cells as the values were negligible for non-viable cells and increased with an increase in abundance. Through this study, the utility of Fv and σPSII (functional-absorption-cross-section of photosystem II) along with F0 and Fv/Fm in providing additional information on cell-viability and algal-size group during assessment is discussed. The findings will have implications not only from the perspective of ballast water but also in testing/assays of specific interest (e.g. toxicity, water treatments, antifouling) and ecological studies involving microalgae.

Effect of CNT/PDMS Nanocomposites on the Dynamics of Pioneer Bacterial Communities in the Natural Biofilms of Seawater.

In this study, the antifouling (AF) performance of different carbon nanotubes (CNTs)-modified polydimethylsiloxane (PDMS) nanocomposites (PCs) was examined directly in the natural seawater, and further analyzed using the Multidimensional Scale Analyses (MDS) method. The early-adherent bacterial communities in the natural biofilms adhering to different PC surfaces were investigated using the single-stranded conformation polymorphism (SSCP) technique. The PCs demonstrated differences and reinforced AF properties in the field, and they were prone to clustering according to the discrepancies within different CNT fillers. Furthermore, most PC surfaces only demonstrated weak modulating effects on the biological colonization and successional process of the early bacterial communities in natural biofilms, indicating that the presence of the early colonized prokaryotic microbes would be one of the primary causes of colonization and deterioration of the PCs. C6 coating seems to be promising for marine AF applications, since it has a strong perturbation effect on pioneer prokaryotic colonization.

Multiple stressors and benthic harmful algal blooms (BHABs): Potential effects of temperature rise and nutrient enrichment

Blooms of Ostreopsis cf. ovata, causing health incidence and mass human intoxications in the Mediterranean, gained special attention over the past decades. To study the potential effects of temperature and nutrient enrichment on this benthic dinoflagellate and other associated microalgae in situ, a multifactorial experiment was set up along a temperature gradient of a heat pump system in Monaco. Microalgae were quantified in experimental units, in the natural biofilm and in the water column. No significant interaction was observed between temperature and nutrients. A species- and bloom phase-dependent effect of the increased temperature was recorded, while the nutrient enrichment had a significant effect only at the end of the experiment (when cell abundances were low). Temperature effects were also visible in the biofilm and the surrounding water. The observed assemblages were mainly driven by changes in abundances of Ostreopsis cf. ovata and Actinocyclus sp., affected in different ways.