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With an ever-increasing amount of plastic pollution in the various aquatic ecosystems around the world, the effects on organisms are still not fully understood. Most studies focus on direct effects posed by plastic intake or entanglement, but plastic debris can also affect primary production of biofilms and have an indirect impact on its consumers. This study investigates the primary production on three common plastic types in freshwater and its food quality for a benthic grazer. We hypothesized that different polymer types affect biofilm composition as well as the life parameters of its consumers. We incubated polyethylene (PE), polyethylene terephthalate (PET) and polystyrene (PS) as well as glass (control) in a productive freshwater creek for natural biofilm establishment. To account for changes in the environmental conditions, the experiment was conducted twice during winter and late spring, respectively. These biofilms were offered to the freshwater gastropod Physa fontinalis as sole food source. Growth and reproduction of the snails were measured to monitor sublethal effects. Additionally, biofilm composition was observed using confocal laser scanning microscopy (CLSM). In winter, snails feeding off PET and PE showed a significantly lower egg production and lower growth rates were observed on PET. No such effects occurred in spring. CLSM data revealed, that algal growth was significantly lower on PE and PET during the winter treatment compared to PS and glass. Since we could only find these effects during the colder and darker months (January-March), the microbial colonization on PE and PET was inhibited by the substrate under less favorable conditions of temperature and light. Hence, benign conditions may mask the adverse effects of microplastic on food webs. Our findings show that future studies on the plastisphere will need to consider such variations to further understand the influence of plastic pollution on primary production and higher trophic levels., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The understanding of biofilm formation by bioleaching microorganisms is of great importance for influencing mineral dissolution rates and to prevent acid mine drainage (AMD). Thermo-acidophilic archaea such as Acidianus, Sulfolobus and Metallosphaera are of special interest due to their ability to perform leaching at high temperatures, thereby enhancing leaching rates. In this work, leaching experiments and visualization by microscopy of cell attachment and biofilm formation patterns of the crenarchaeotes Sulfolobus metallicus DSM 6482(T) and the Acidianus isolates DSM 29038 and DSM 29099 in pure and mixed cultures on sulfur or pyrite were studied. Confocal laser scanning microscopy (CLSM) combined with fluorescent dyes as well as fluorescently labeled lectins were used to visualize different components (e.g. DNA, proteins or glycoconjugates) of the aforementioned species. The data indicate that cell attachment and the subsequently formed biofilms were species- and substrate-dependent. Pyrite leaching experiments coupled with pre-colonization and further inoculation with a second species suggest that both species may negatively influence each other during pyrite leaching with respect to initial attachment and pyrite dissolution rates. In addition, the investigation of binary biofilms on pyrite showed that both species were heterogeneously distributed on pyrite surfaces in the form of individual cells or microcolonies. Physical contact between the two species seems to occur, as revealed by specific lectins able to specifically bind single species within mixed cultures., (Copyright © 2016 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Streams and rivers are important sites of organic carbon mineralization which is dependent on the land use within river catchments. Here we tested whether planktonic and epilithic biofilm bacteria differ in their response to the quality of dissolved organic carbon (DOC). Thus, planktonic and biofilm bacterial production was compared with patterns of DOC along a land-use gradient in the Bode catchment area (Germany). The freshness index of DOC was positively related to the proportion of agricultural area in the catchment. The humification index correlated with the proportion of forest area. Abundance and production of planktonic bacteria were lower in headwaters than at downstream sites. Planktonic production was weakly correlated to the total concentration of DOC but more strongly to quality-measures as revealed by spectra indexes, i.e. positively to the freshness index and negatively to the humification index. In contrast to planktonic bacteria, abundance and production of biofilm bacteria were independent of DOC quality. This finding may be explained by the association of biofilm bacteria with benthic algae and an extracellular matrix which represent additional substrate sources. The data show that planktonic bacteria seem to be regulated at a landscape scale controlled by land use, whereas biofilm bacteria are regulated at a biofilm matrix scale controlled by autochthonous production. Thus, the effects of catchment-scale land use changes on ecosystem processes are likely lower in small streams dominated by biofilm bacteria than in larger streams dominated by planktonic bacteria., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Shewanellaceae are among the most widely studied electroactive microorganisms. In this report, we studied the influence of the applied electrode potential on the anodic current production of Shewanella putrefaciens NCTC 10695 under anoxic conditions. Furthermore, we used cyclic voltammetry (CV) and confocal laser scanning microscopy (CLSM) to investigate the microbial electron transfer and biofilm formation. It is shown that the chronoamperometric current density is increasing with increasing electrode potential from 3 μA cm(-2) at -0.1 V up to -12 μA cm(-2) at +0.4 V (vs. Ag/AgCl), which is accompanied by an increasing amount of biomass deposited on the electrode. By means of cyclic voltammetry we demonstrate that direct electron transfer (DET) is dominating and the planktonic cells play only a minor role., (2012 Elsevier B.V. All rights reserved)