Effect of increasing salinity to adapted and non-adapted Anammox biofilms.

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-1 did 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 50 g 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 NO2- / NH4+ 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.

Highly efficient long-term storage of carrier-bound anammox biomass.

The anammox process is a potential alternative to the conventional nitrogen removal from wastewater. However, due to large generation times of anammox bacteria, the start-up of treatment reactors may be impeded. An efficient storage technique can handle this drawback and may be also suitable for seasonally operated treatment plants like in touristic areas. In the current study, several storage techniques were investigated with respect to its suitability for the preservation of the specific anammox activity after long-term storage. Storing conditions differed in terms of temperature, redox buffer and nutrient supplementation. The specific activity of immobilized anammox bacteria (Candidatus Kuenenia stuttgartiensis) was determined three times during a long-term preservation of 78 days and 106 days, respectively. The highest activity was ensured at a storing temperature of 4 °C, providing nitrate as redox buffer and a nutrient supplement every 23 days. Thus, 91.4% of the initial anammox activity could be preserved after a storage of 106 days. Superiority of the presented treatment condition was confirmed by a calculated nitrate-ammonium consumption rate close to the optimal ratio of 1.32. This technique provided an economical and simple method suitable for long-term storage of immobilized anammox biomass.

The precision of bacterial quantification techniques on different kinds of environmental samples and the effect of ultrasonic treatment.

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.

In vitro-differentiated embryonic stem cells give rise to male gametes that can generate offspring mice.

Male gametes originate from a small population of spermatogonial stem cells (SSCs). These cells are believed to divide infinitely and to support spermatogenesis throughout life in the male. Here, we developed a strategy for the establishment of SSC lines from embryonic stem (ES) cells. These cells are able to undergo meiosis, are able to generate haploid male gametes in vitro, and are functional, as shown by fertilization after intracytoplasmic injection into mouse oocytes. Resulting two-cell embryos were transferred into oviducts, and live mice were born. Six of seven animals developed to adult mice. This is a clear indication that male gametes derived in vitro from ES cells by this strategy are able to induce normal fertilization and development. Our approach provides an accessible in vitro model system for studies of mammalian gametogenesis, as well as for the development of new strategies for the generation of transgenic mice and treatment of infertility.