The impact of different operating conditions on membrane fouling and EPS production

The main goal of this research was to investigate how different factors influence membrane fouling. The impact of the different concentrations of activated sludge and the amount of extracellular polymer substances (EPS) were monitored. Two pilot plants with submerged membrane modules (hollow fiber and flat sheet) were operated and the raw wastewater was used.Humic substances were identified as the major components of EPS in the activated sludge (more than 34%) in both pilot plants. As the basic constituent in permeate, humic substances were identified as the most dominant components in the effluent (61%) in both pilot plants. Conversely, proteins were mostly analyzed in permeate and supernatant below the detection limit. The total amount of EPS [mg g⁻¹ (VSS)] was similar for concentrations of activated sludge 6, 10 and 14 g L⁻¹. Carbohydrates were identified as the component of EPS which tends most to clog membranes.     

Die „Zähluhr”

Ohne Zusammenfassung     

Community Assembly of Terrestrial Testate Amoebae: How is the Very First Beginning Characterized?

Testate amoebae play an important role at the very first beginning of succession on land. We used litterbags buried into four different soils to study the early colonization (which occurred within less than 55 days) and establishment of testate amoebae. The litterbag cellulose exposed at the youngest mining site poor in nitrogen and phosphorus was colonized firstly in high abundances, whereas the substrate introduced into the reference sites of undisturbed soil was colonized slowly and in low densities. Besides the (expected) small-sized r-strategists (e.g., Euglypha rotunda, Tracheleuglypha dentata, and Trinema lineare), large-sized K-strategists (e.g., Centropyxis spp., Phryganella acropodia) occurred in remarkably high densities on all sites. Species that colonized the cellulose in high densities (e.g., P. acropodia and T. dentata) were found extremely rarely in the adjacent source substrate and vice versa, stressing the importance of the target substrate quality. In the course of the experiment, the influencing environmental factors became more complex, as shown by redundancy analysis (RDA). Concerning the amoebal community, there was a change from variability to stability, as visualized by cluster analysis. Adjacent litterbags within an investigation site revealed amoebal species and abundances with an increasing similarity during exposition time, whereas the litterbags between the four investigation sites were colonized differently. These observations point to a stochastic (variable) beginning of community assembly, changing to a more deterministic (stable) course. No species replacement has been observed, which is an essential part of most successional theories. Thus, the more flexible concept of "community assembly" should be considered instead of "succession" for protozoa. The stochastic beginning of community assembly and the lack of species replacement are explained by a neutral community model.     

A 71-kDa protein from Halobacterium salinarium belongs to a ubiquitous P-loop ATPase superfamily with head-rod-tail structure

The nucleotide sequence of a genomic fragment from Halobacterium salinarium containing an open reading frame encoding a protein with a calculated molecular mass of 71 kDa was determined. Database searches revealed that this protein, Hp71, has similarities to eukaryotic cytoskeletal proteins. Heterologous production of Hp71 in Escherichia coli allowed the isolation of anti-Hp71 antibodies. The antibodies were used (1) to verify the production of Hp71 in H. salinarium and (2) to determine its cytoplasmic localization by immune electron microscopy. Homologous overproduction of Hp71 in H. salinarium and heterologous production in Haloferax volcanii resulted in modifications of cell morphology from rods to extended rods, and from pleiomorphic cells to rods, respectively. Structure prediction methods indicated that Hp71 has a head-rod-tail configuration, including an N-terminal domain with a nucleotide binding motif (P-loop), and an extended discontinuous coiled-coil domain of 330 amino acids. To identify related proteins, the complete genomes of Haemophilus influenzae, Mycoplasma genitalium, and Methanococcus jannaschii were searched for deduced proteins with extended coiled-coil domains. Only one or two proteins were found for each organism, showing that Hp71 is one of only a few prokaryotic intracellular proteins with extended coiled-coil domains. The phenotype upon overproduction and the similarity of Hp71 to the SMC superfamily of P-loop head-rod-tail proteins (named after SMC1, which is involved in the “stability of minichromosomes” in yeast) indicate that Hp71 might be involved in cytoskeleton formation and/or chromosome partitioning in H. salinarium. Received: 25 March 1997 / Accepted: 11 August 1997     

Relative brain size: A critique of a new measure

An analysis of a relative brain size measuring technique proposed by Radinsky ('67) shows it to be inapplicable on lower taxonomic levels of primates. The relationship among foramen magnum area, total skeletal weight (a suggested index of body size) and cranial capacity are analyzed by a partial correlation technique. Results indicate that foramen magnum size is significantly associated with total skeletal weight through its relationship to cranial capacity.