Biocoenosis and degradation in model wastewater treatment plants

Summary The bacteria and protozoa of laboratory models for wastewater treatment plants have been determined and compared to species from ordinary plants. A determination key specially designed for the bacteria of wastewater treatment plants has been developed. Large changes in the composition of the bacterial populations were found in the model open laboratory plant system. Tests with a model sterile closed plant and reproducible inoculum have been performed to get a constant bacteria population to improve the comparability and reproducibility for substance degradation test.     

Skerotin-Komponenten in den Vitellocyten von Microdalyellia fairchildi (Turbellaria)

Zusammenfassung 1. An Microdalyellia fairchildi (Turbellaria, O. Neorhabdocoela) wird im Hinblick auf die chemische Natur der Eischalen das Vorkommen der Grundkomponenten des Sklerotins (Phenole, NH₂-reiche Proteine, Phenoloxidase) histo- und cytochemisch überprüft.2. An Totalpräparaten, histologischen Schnitten und isolierten Vitellocyten werden alle drei Komponenten in sogenannten Schalenvesikeln der Dotterzellen nachgewiesen, die hier neben anderen nährstoffhaltigen Vesikeln vorliegen. Für andere Gewebe und Organe, insbesondere die sogenannten Schalendrüsen, sind die ausgeführten Tests im wesentlichen negativ. Die Sklerotin-Natur der Eischalen ist damit nach entsprechenden Befunden an zahlreichen Trematoden und einigen Cestoden auch für eine Turbellarien-Gruppe erstmals erwiesen.3. Die Verwendung von H3-Tyrosin zeigt eine beträchtliche Anreicherung dieser Aminosäure in den Vitellarien sowie eine starke Beteiligung am Aufbau der Eischalen. Die Vermutung, daß die Phenolkomponente aus Tyrosin hervorgeht und an der Brückenbildung der Proteinketten beteiligt ist, bleibt zu erweisen.4. Bemerkenswert ist, daß sich die Aktivität der Phenoloxidase der Vesikel zwar auf Brenzcatechin, nicht aber auf Dopa (3,4-Dihydroxyphenylalanin) erstreckt; hierin weicht sie von den biochemischen Befunden extrahierter Phenoloxidasen verschiedener Herkunft ab. Mit verschiedenen Schwermetallkomplexbildnern (Natriumdiäthyldithiocarbaminat, D-Penicillamin) ist Inhibition möglich.

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Sclerotin precursors in the vitelline cells of Microdalyellia fairchildi (Turbellaria)

Summary 1. In Microdalyellia fairchildi (Turbellaria, O. Neorhabdocoela) the occurrence of sclerotin precursors (phenolic substance, phenoloxidase, NH₂-rich protein) is histo- and cytochemically tested.2. In whole mount preparations, histological sections and isolated vitelline cells the three components could be demonstrated in special vesicles of the vitelline cells, which are present here along with nutrient vesicles. For other tissues and organs the tests were generally negative, especially for the so-called shell glands. After several corresponding results in many trematodes and in some cestodes the sclerotin nature of egg capsules seems now to be well-founded for a group of turbellaria too.3. Tritium-labeled tyrosine, which is ingested with food, is markedly enriched in the vitellaria and shown to be an essential ingredient of the egg-shell material. But the idea that this tyrosine is the precursor of the phenolic substance and thus possibly participates in cross-linking the protein chains of sclerotin remains to be confirmed.4. It is shown that the phenoloxidase of the vesicles catalyzes the oxidation of catechol but not that of Dopa (3,4-dihydroxyphenylalanine), a finding different from several biochemical investigations of the enzyme taken from other sources. Inhibition of the enzyme with some heavy metal complex-binding compounds (sodium diethyldithiocarbaminate, D-penicillamine) is demonstrated.

     

Virulence of Agrobacterium tumefaciens requires lipid homeostasis mediated by the lysyl‐phosphatidylglycerol hydrolase AcvB

Agrobacterium tumefaciens transfers oncogenic T‐DNA via the type IV secretion system (T4SS) into plants causing tumor formation. The acvB gene encodes a virulence factor of unknown function required for plant transformation. Here we specify AcvB as a periplasmic lysyl‐phosphatidylglycerol (L‐PG) hydrolase, which modulates L‐PG homeostasis. Through functional characterization of recombinant AcvB variants, we showed that the C‐terminal domain of AcvB (residues 232–456) is sufficient for full enzymatic activity and defined key residues for catalysis. Absence of the hydrolase resulted in ~10‐fold increase in L‐PG in Agrobacterium membranes and abolished T‐DNA transfer and tumor formation. Overproduction of the L‐PG synthase gene (lpiA) in wild‐type A. tumefaciens resulted in a similar increase in the L‐PG content (~7‐fold) and a virulence defect even in the presence of intact AcvB. These results suggest that elevated L‐PG amounts (either by overproduction of the synthase or absence of the hydrolase) are responsible for the virulence phenotype. Gradually increasing the L‐PG content by complementation with different acvB variants revealed that cellular L‐PG levels above 3% of total phospholipids interfere with T‐DNA transfer. Cumulatively, this study identified AcvB as a novel virulence factor required for membrane lipid homeostasis and T‐DNA transfer.