Antagonistic microbial interactions: Contributions and potential applications for controlling pathogens in the aquatic systems.

Despite the active and intense treatment of wastewater, pathogenic microorganisms and viruses are frequently introduced into the aquatic environment. For most human pathogens, however, this is a rather hostile place, where starvation, continuous inactivation, and decay generally occur, rather than successful reproduction. Nevertheless, a great diversity of the pathogenic microorganisms can be detected, in particular, in the surface waters receiving wastewater. Pathogen survival depends majorly on abiotic factors such as irradiation, changes in water ionic strength, temperature, and redox state. In addition, inactivation is enhanced by the biotic interactions in the environment. Although knowledge of the antagonistic biotic interactions has been available since a long time, certain underlying processes and mechanisms still remain unclear. Others are well-appreciated and increasingly are applied to the present research. Our review compiles and discusses the presently known biotic interactions between autochthonous microbes and pathogens introduced into the aquatic environment, including protozoan grazing, virus-induced bacterial cell lysis, antimicrobial substances, and predatory bacteria. An overview is provided on the present knowledge, as well as on the obvious research gaps. Individual processes that appear promising for future applications in the aquatic environment are presented and discussed

Mo- and W-Fiber Reinforced SiCN Ceramic Matrix Composites based on PIP process

Mo- and W-fiber reinforced CMCs can be easily manufactured via polymer infiltration and pyrolysis at 1300 °C (PIP) Mo/SiCN and W/SiCN composites are light-weight in comparison to Mo/Mo and W/W composites Mo/SiCN and W/SiCN show increased fracture strain compared to CMCs Mo/SiCN and W/SiCN can be considered as WMCs and thus need no weak interphase Microstructural and phase analyses have shown that Mo- and W-fibers are still present and thermally resistant in the SiCN matrix even at 1300 °C Thermodynamical calculations strongly recommend an additional fiber coating from C-attack! Microstructural and phase analyses have shown that Mo- and W-fibers suffer from surfacial attack, mainly by C-based materials Applying a coating as reaction barrier (e.g. Y2O3) should provide further improvement in mechanical properties New applications are feasible due to: increased fracture strain good tensile and fracture strain high stiffness high thermal conductivity low thermal expansion high thermal shock resistance anisotropic behaviour of composite according to tailor-made desig

Mo- and W-Fiber Reinforced SiCN Ceramic Matrix Composites based on PIP process

Mo- and W-fiber reinforced CMCs can be easily manufactured via polymer infiltration and pyrolysis at 1300 °C (PIP) Mo/SiCN and W/SiCN composites are light-weight in comparison to Mo/Mo and W/W composites Mo/SiCN and W/SiCN show increased fracture strain compared to CMCs Mo/SiCN and W/SiCN can be considered as WMCs and thus need no weak interphase Microstructural and phase analyses have shown that Mo- and W-fibers are still present and thermally resistant in the SiCN matrix even at 1300 °C Thermodynamical calculations strongly recommend an additional fiber coating from C-attack! Microstructural and phase analyses have shown that Mo- and W-fibers suffer from surfacial attack, mainly by C-based materials Applying a coating as reaction barrier (e.g. Y2O3) should provide further improvement in mechanical properties New applications are feasible due to: increased fracture strain good tensile and fracture strain high stiffness high thermal conductivity low thermal expansion high thermal shock resistance anisotropic behaviour of composite according to tailor-made desig

Antagonistic Microbial Interactions: Contributions and Potential Applications for Controlling Pathogens in the Aquatic Systems

Despite the active and intense treatment of wastewater, pathogenic microorganisms and viruses are frequently introduced into the aquatic environment. For most human pathogens, however, this is a rather hostile place, where starvation, continuous inactivation, and decay generally occur, rather than successful reproduction. Nevertheless, a great diversity of the pathogenic microorganisms can be detected, in particular, in the surface waters receiving wastewater. Pathogen survival depends majorly on abiotic factors such as irradiation, changes in water ionic strength, temperature, and redox state. In addition, inactivation is enhanced by the biotic interactions in the environment. Although knowledge of the antagonistic biotic interactions has been available since a long time, certain underlying processes and mechanisms still remain unclear. Others are well-appreciated and increasingly are applied to the present research. Our review compiles and discusses the presently known biotic interactions between autochthonous microbes and pathogens introduced into the aquatic environment, including protozoan grazing, virus-induced bacterial cell lysis, antimicrobial substances, and predatory bacteria. An overview is provided on the present knowledge, as well as on the obvious research gaps. Individual processes that appear promising for future applications in the aquatic environment are presented and discussed

Novel ceramic matrix composites with tungsten and molybdenum fiber reinforcement

Ceramic matrix composites usually utilize carbon or ceramic fbers as reinforcements. However, such fbers often expose a low ductility during failure. In this work, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fbers to reach pseudo ductile behavior during failure. Tungsten and molybdenum fbers were chosen as reinforcement in SiCN ceramic matrix composites manufactured by polymer infltration and pyrolysis process. The composites were investigated with respect to microstructure, flexural- and tensile strength. The single fber strengths for both tungsten and molybdenum were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. The W fber became brittle across the entire cross section, while the Mo fber showed a superfcial, brittle reaction zone but kept ductile on the inside

Novel ceramic matrix composites with tungsten and molybdenum fiber reinforcement

Damage-tolerant ceramic matrix composites (CMC) are prone to high temperature applications under severe environmental conditions and usually utilize carbon or ceramic fibres (e.g. SiC) as reinforcements of ceramic matrices with inherent low elongation to break compared to common metals. However, CMC reveal an elongation to break and stiffness similar to the ceramic matrices, and thus need a fibre coating in order to improve the elongation to break length and thus to achieve damage tolerance of the composite. In addition, such fibers often expose a low ductility during failure. As a consequence, design criteria for components of such CMC materials are limited by the low strain of failure. In order to overcome this problem, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fibres to reach pseudo ductile behaviour during failure. Tungsten (W) and molybdenum (Mo) fibers were chosen as reinforcement in SiCN CMC manufactured by polymer infiltration and pyrolysis process. These fibres are commercially available since they are widespread used in light bulbs, etc. , and possess an intrinsic higher elongation to break, compared to ceramic fibres, as well as high stiffness even at high temperatures. W/SiCN and Mo/SiCN composites were manufactured via filament winding and resin transfer moulding of commercially available polysilazanes, pyrolysed and re-densified by multiple reinfiltration and pyrolysis steps. These composites were investigated with respect to microstructure, flexural and tensile strength. Single fibre strengths for W and Mo were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. W fibre became brittle across the entire cross section, while the Mo fibre showed a superficial, brittle reaction zone but kept ductile on the inside

Grazing of heterotrophic flagellates on viruses is driven by feeding behaviour

The trophic interactions between viruses, bacteria and protists play a crucial role in structuring microbial communities and regulating nutrient and organic matter flux. Here, we show that the impact on viral density by heterotrophic flagellates is related to their feeding behaviour (feeding on sedimented particles Thaumatomonas coloniensis, filter feeding of suspended particles - Salpingoeca sp., and actively searching raptorial feeding - Goniomonas truncata). Phage MS2 was co-incubated with flagellates and the natural bacterial and viral community originating from the same groundwater habitats where the flagellates were isolated. Three complementary assays, i.e. flow cytometry, qPCR and plaque assay, were used for enumeration of total viruses, total MS2 phages, and free and infectious MS2, respectively, to provide insights into the grazing mechanisms of the flagellates on viruses. Phage MS2 was actively removed by the suspension feeders T. coloniensis and Salpingoeca sp. in contrast with the actively raptoriale grazer G. truncata. The decline of viral titre was demonstrated to be caused by ingestion rather than random absorption by both qPCR and locating protein fluorescently labelled MS2 inside the flagellates. Further, we indicate that phages can be used as a minor carbon source for flagellates. Collectively, these data demonstrate that eliminating viruses can be an important function of protists in microbial food webs, carbon cycling and potentially water quality control