Microplastic particles entering aquatic systems are rapidly colonized by microbial biofilms. The presence of microbial biomass may cause sinking of particles and as a consequence prevent their ...transport to the oceans. We studied microbial colonization of different polymer particles exposed in the epi-, meta- and hypolimnion of a freshwater reservoir during late summer for 47 days. Parameters measured included biofilm formation, metal sorption and sinking velocities. Microbial biofilms contained bacteria, cyanobacteria and algae as well as inorganic particles such as iron oxides. Regardless of biofilm thickness and biovolumes of different biofilm constituents, single polyethylene (PE) particles stayed buoyant, whereas the sinking velocity of single polystyrene (PS) and polyethylene terephthalate (PET) particles did not change significantly compared to initial values. During exposition, a mixing event occurred, by which anoxic, iron-rich water from the hypolimnion was mixed with water from upper layers. This induced aggregation and sinking of hypolimnetic PE particles together with organic matter, cyanobacteria colonies and iron minerals.
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•Biofouling did not facilitate sinking of single microplastics within a temperate mesotrophic reservoir.•Colonization of phototrophic organisms was different between plastic polymer types.•Substantial amounts of iron and manganese sorbed to biofilm covered microplastics.
Microbial biofilms can be both cause and cure to a range of emerging societal problems including antimicrobial tolerance, water sanitation, water scarcity and pollution. The identities of ...extracellular polymeric substances (EPS) responsible for the establishment and function of biofilms are poorly understood. The lack of information on the chemical and physical identities of EPS limits the potential to rationally engineer biofilm processes, and impedes progress within the water and wastewater sector towards a circular economy and resource recovery. Here, a multidisciplinary roadmap for addressing this EPS identity crisis is proposed. This involves improved EPS extraction and characterization methodologies, cross-referencing between model biofilms and full-scale biofilm systems, and functional description of isolated EPS with in situ techniques (e.g. microscopy) coupled with genomics, proteomics and glycomics. The current extraction and spectrophotometric characterization methods, often based on the principle not to compromise the integrity of the microbial cells, should be critically assessed, and more comprehensive methods for recovery and characterization of EPS need to be developed.
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•Extracellular polymeric substances feature in key societal problems (clinical, environmental).•Methods and standards of EPS recovery and characterization need to be critically assessed.•More emphasis should be placed on methods that enable identification (chemical and function).•Integrated and multi-displinary analyses are required on biofilms and EPS isolates.•Will improve biofilm management and enable a more circular economy in water and waste.
Freshwater tufa deposits are the result of calcification associated with biofilms dominated by cyanobacteria. Recent investigations highlighted the fact that the formation of microbial calcium ...carbonates is mainly dependent on the saturation index, which is determined by pH, the ion activity of Ca²⁺ and CO₃²⁻, and the occurrence of extracellular polymeric substances (EPS) produced by microorganisms. EPS, which contain carboxyl and/or hydroxyl groups, can strongly bind cations. This may result in inhibition of CaCO₃ precipitation. In contrast, the formation of templates for crystal nucleation was reported by many previous investigations. The purposes of this study were (i) to characterize the in situ distribution of EPS glycoconjugates in tufa-associated biofilms of two German hard-water creeks by employing fluorescence lectin-binding analysis (FLBA), (ii) to verify the specific lectin-binding pattern by competitive-inhibition assays, and (iii) to assess whether carbonates are associated with structural EPS domains. Three major in situ EPS domains (cyanobacterial, network-like, and cloud-like structures) were detected by FLBA in combination with laser scanning microscopy (LSM). Based on lectin specificity, the EPS glycoconjugates produced by cyanobacteria contained mainly fucose, amino sugars (N-acetyl-glucosamine and N-acetyl-galactosamine), and sialic acid. Tufa deposits were irregularly covered by network-like EPS structures, which may originate from cyanobacterial EPS secretions. Cloud-like EPS glycoconjugates were dominated by sialic acid, amino sugars, and galactose. In some cases calcium carbonate crystals were associated with cyanobacterial EPS glycoconjugates. The detection of amino sugars and calcium carbonate in close association with decaying sheath material indicated that microbially mediated processes might be important for calcium carbonate precipitation in freshwater tufa systems.
ANaerobic AMMonium OXidation (anammox) is an established process for efficient nitrogen removal from wastewater, relying on anammox bacteria to form stable biofilms or granules. To understand the ...formation, structure, and stability of anammox granules, it is important to determine the composition of the extracellular polymeric substances (EPS). The aim of this research was to elucidate the nature of the proteins, which are the major fraction of the EPS and were suspected to be glycosylated. EPS were extracted from full-scale anammox granular sludge, dominated by “Candidatus Brocadia”, and subjected to denaturing polyacrylamide gel electrophoresis. By further analysis with mass spectrometry, a high abundant glycoprotein, carrying a heterogeneous O-glycan structure, was identified. The potential glycosylation sequence motif was identical to that proposed for the surface layer protein of “Candidatus Kuenenia stuttgartiensis”. The heavily glycosylated protein forms a large fraction of the EPS and was also located by lectin staining. Therefore, we hypothesize an important role of glycoproteins in the structuring of anammox granules, comparable to the importance of glycans in the extracellular matrix of multicellular organisms. Furthermore, different glycoconjugates may have distinct roles in the matrix of granular sludge, which requires more in-depth characterization of different glycoconjugates in future EPS studies.
A model for the biofilm growth by Acidianus sp. DSM 29099 on pyrite is given. In the first stage (24–48 h), reversible attachment is possible. It is accompanied by the production of adhesive ...compounds on the mineral surface. Biofilm formation on pyrite by Acidianus sp. DSM 29099 is a dynamic process accompanied by formation of pits and production of adhesive compounds, which after cell detachment remain as footprints.
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•In situ visualization of biofilms and EPS of thermoacidophilic archaea on pyrite.•Direct detection of footprints of cells of Acidianus sp. DSM 29099.•EPS extraction and analysis of Acidianus in bioleaching environments.•Suggestion of a model for biofilm formation by Acidianus sp.
Bioleaching of metal sulfides represents an interfacial process where biofilm formation is important in the initial steps of this process. In technical applications of bioleaching, such as reactor leaching in the temperature range of 50 up to 90 °C and also in (self-heating) heaps, thermophilic archaea play an important role and often are the leaching organisms of choice. Nevertheless, to date there is little information available on the interactions between thermoacidophilic archaea and their natural mineral substrates such as pyrite. Especially for extracellular polymeric substances (EPS) of archaea and their biofilms in bioleaching environments information is rather limited. The present work focused on investigations of biofilm dynamics and EPS production of the thermoacidophilic archaeon Acidianus sp. DSM 29099 under bioleaching conditions. The results show that biofilms are dispersed non-homogeneously on pyrite. Large parts of the pyrite surfaces remain free of cells. Cell detachment from pyrite results in microbial “footprints” which, based on lectin binding assays, consist of mannose, glucose and fucose containing compounds. A monolayer biofilm develops on pyrite after 2–4 days of incubation. In addition, the pyrite surface is covered with a layer of organic compounds. EPS analysis indicates the presence of proteins, polysaccharides and uronic acids, the composition of which varies according to substrate and lifestyle (i.e. planktonic, biofilm cells). This report provides insight into EPS and biofilm characteristics of thermophilic archaea and improves understanding of the mineral-microbial-biofilm interfacial interactions in extreme environments. Moreover, the results on interaction dynamics of archaeal microbial consortia will facilitate the understanding of thermophilic bioleaching.
Environmental biofilms represent a complex mixture of different microorganisms. Their identity is usually analyzed by means of nucleic acid-based techniques. However, these biofilms are also composed ...of a highly complex extracellular matrix produced by the microbes within a particular biofilm system. The biochemical identity of this extracellular matrix remains in many cases an intractable part of biofilms and bioaggregates. Consequently, there is a need for an approach that will give access to the fully hydrated structure of the extracellular matrix or at least a major part of it. A crucial compound of the matrix identified as carbohydrate-based polymers represents major structural and functional constituents. These glycoconjugates can be characterized by using fluorescently-labeled lectins in combination with confocal laser scanning microscopy. The lectin approach is defined previously, as fluorescence lectin barcoding (FLBC) and fluorescence lectin-binding analysis (FLBA), where FLBC is equal to the screening of a particular sample with all the commercially available lectins and FLBA is the actual analysis of the matrix throughout an experiment with a selected panel of lectins. As the application of immune-based techniques in environmental biofilm systems is impossible, the lectin approach is currently the only option for probing lectin-specific glycoconjugates in complex biofilms and bioaggregates. From all the commercially available lectins tested, the lectins such as AAL, HAA, WGA, ConA, IAA, HPA, and LEA showed the highest binding efficiency. Furthermore, 20 of the overall lectins tested showed an intermediate signal intensity, nevertheless very useful for the assessment of matrix glycoconjugates. With the data compiled, we shall virtually shed more light on the dark matter of the extracellular matrix and their 3-dimensional distribution in environmental biofilm systems. The results will be helpful in future studies with a focus on the extracellular matrix glycoconjugates present in environmental microbial communities.
Plasma wall interaction (PWI) is important for the material choice in ITER and for the plasma scenarios compatible with material constraints. In this paper, different aspects of the PWI are assessed ...in their importance for the initial wall materials choice: CFC for the strike point tiles, W in the divertor and baffle and Be on the first wall. Further material options are addressed for comparison, such as W divertor/Be first wall and all-W or all-C. One main parameter in this evaluation is the particle flux to the main vessel wall. One detailed plasma scenario exists for a
Q
=
10 ITER discharge G. Federici et al., J. Nucl. Mater. 290–293 (2001) 260 which was taken as the basis of further erosion and tritium retention evaluations. As the assessment of steady state wall fluxes from a scaling of present fusion devices indicates that global wall fluxes may be a factor of 4
±
3 higher, this margin has been adopted as uncertainty of the scaling. With these wall and divertor fluxes, important PWI processes such as erosion and tritium accumulation have been evaluated: It was found that the steady state erosion is no problem for the lifetime of plasma-facing divertor components. Be wall erosion may pose a problem in case of a concentration of the wall fluxes to small wall areas. ELM erosion may drastically limit the PFC lifetime if ELMs are not mitigated to energies below 0.5
MJ. Dust generation is still a process which requires more attention. Conversion from gross or net erosion to dust and the assessment of dust on hot surfaces need to be investigated. For low-
Z materials the build-up of the tritium inventory is dominated by co-deposition with eroded wall atoms. For W, where erosion and tritium co-deposition are small, the implantation, diffusion and bulk trapping constitute the dominant retention processes. First extrapolations with models based on laboratory data show small contributions to the inventory. For later ITER phases and the extrapolation to DEMO additional tritium trapping sites due to neutron-irradiation damage need to be taken into account. Finally, the expected values for erosion and tritium retention are compared to the ITER administrative limits for the lifetime, dust and tritium inventory.
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