TY - GEN A1 - Rathsack, Kristina A1 - Böllmann, Jörg A1 - Martienssen, Marion T1 - Comparative Study of Different Methods for Analyzing Denitrifying Bacteria in Fresh Water Ecosystems T2 - Journal of Water Resource and Protection N2 - Bacteria capable of denitrification play a significant role in the nitrogen cycle of freshwater ecosystems. By metabolizing nitrogen compounds they e.g. counteract the eutrophication of natural waters. To get detailed insights into the in situ turnover rates of nitrogen a reliable tool of quantification for active microorganisms is essential. In the present investigation, quantification capabilities of a molecular tool (Polymerase Chain Reaction—PCR) and a cultivation based tool (Most probable number—MPN) were investigated and compared. The total bacterial concentration yielded by the molecular PCR approach was up to 6-fold higher compared to the results of the MPN approach. However, the portion of culturable denitrifying bacteria compared to the number of specific gene copies (nirS) was much lower. Depending on the environmental conditions, the difference between the PCR and the MPN approach was up to three orders of magnitude. From lab scale experiments with a pure P. aeroginosa strain it can be concludes, that these differences are not the result of inappropriate culture conditions but rather reflect the portion of so called viable but not culturable bacteria (VBNC). Low nitrate concentrations as found in many fresh water ecosystems induced a significant increase in the portion of non culturable denitrifying bacteria. Referred to the investigation of dynamic populations, the number of metabolic active bacteria is represented by the MPN rather than by the PCR approach. Y1 - 2014 SN - 1945-3094 SN - 1945-3108 VL - 6 IS - 6 SP - 609 EP - 617 ER - TY - GEN A1 - Böllmann, Jörg A1 - Rathsack, Kristina A1 - Martienssen, Marion T1 - The precision of bacterial quantification techniques on different kinds of environmental samples and the effect of ultrasonic treatment T2 - Journal of Microbiological Methods N2 - The precision of cell number quantification in environmental samples depends on the complexity of the sample and on the applied technique. We compared fluorescence microscopy after filtration, quantification of gene copies and the cultivation based most probable number technique for their precision. We further analyzed the effect of increasing complexity of the sample material on the precision of the different methods by using pure cultures of Pseudomonas aeruginosa, fresh water samples and sediment slurries with and without ultrasonic treatment for analyses. Microscopy reached the highest precision, which was similar between pure cultures and water samples, but lower for sediment samples due to a higher percentage of cells in clusters and flocks. The PCR based quantification was most precise for pure cultures. Water and sediment samples were similar but less precise, which might be caused by the applied DNA extraction techniques. MPN measurements were equally precise for pure cultures and water samples. For sediment slurries the precision was slightly lower. The applied ultrasonic treatment of the slurries dispersed the cell clusters and flocks, increased the precision of microscopical and MPN measurements and also increased the number of potential colony forming units. However, the culturable cell number decreased by half. For MPN quantification of viable cells in samples with a high proportion of clustered cells we therefore recommend an optimization of ultrasonic treatment and a confirmation by microscopy and cultivation to reach highest possible dispersion of the cells with a minimum of inactivation. As a result of these observations we suggest a correction factor for MPN measurements to consider the effect of sonication on complex samples. The results are most likely applicable to other complex samples such as soil or biofilms. Y1 - 2016 U6 - https://doi.org/10.1016/j.mimet.2016.05.006 SN - 0167-7012 VL - 126 SP - 42 EP - 47 ER - TY - GEN A1 - Engelbrecht, Steffen A1 - Mozooni, Mohammad A1 - Rathsack, Kristina A1 - Böllmann, Jörg A1 - Martienssen, Marion T1 - Effect of increasing salinity to adapted and non-adapted Anammox biofilms T2 - Environmental Technology N2 - The Anammox process is an efficient low energy alternative for the elimination of nitrogen from wastewater. The process is already in use for side stream applications. However, some industrial wastewaters, e.g. from textile industry are highly saline. This may be a limit for the application of the Anammox process. The aim of this study was to evaluate the effects of different NaCl concentrations on the efficiency of adapted and non-adapted Anammox biofilms. The tested NaCl concentrations ranged from 0 to 50 g NaCl*L⁻¹. Concentrations below 30 g NaCl*L⁻¹did not significantly result in different nitrogen removal rates between adapted and non-adapted bacteria. However, adapted bacteria were significantly more resilient to salt at higher concentrations (40 and 50g NaCl*L⁻¹). The IC50 for adapted and non-adapted Anammox bacteria were 19.99 and 20.30 g NaCl*L⁻¹, respectively. Whereas adapted biomass depletes the nitrogen in ratios of NO-₂/NH+₄ around 1.20 indicating a mainly Anammox-driven consumption of the nitrogen, the ratio increases to 2.21 at 40 g NaCl*L⁻¹ for non-adapted biomass. This indicates an increase of other processes like denitrification. At lower NaCL concentrations up to 10 g NaCl*L⁻¹, a stimulating effect of NaCl to the Anammox process has been observed. KW - Adapted KW - Anammox KW - Biofilm KW - Non-adapted KW - Salinity Y1 - 2019 U6 - https://doi.org/10.1080/09593330.2018.1455748 SN - 0959-3330 SN - 1479-487X VL - 40 IS - 22 SP - 2880 EP - 2888 ER - TY - GEN A1 - Martienssen, Marion A1 - Böllmann, Jörg A1 - Nixdorf, Brigitte A1 - Rathsack, Kristina T1 - Calculation of hypolimnic denitrification in a dimictic freshwater lake during summer stratification T2 - Aquatic Microbial Ecology KW - Denitrification KW - freshwater Y1 - 2019 U6 - https://doi.org/10.3354/ame01911 SN - 0948-3055 SN - 1616-1564 VL - 83 IS - 2 SP - 189 EP - 201 ER -