Enzymatischer Abbau der Membranen von Oscillatoria amoena (Kütz.) Gomont mit Lysozym

Ohne Zusammenfassung     

Cytochemisch-elektronenmikroskopische Lokalisierung der Ribonukleinsäure und des Assimilats in Cyanophyceen

Zusammenfassung Mit cytochemisch-elektronenmikroskopischen Methoden wird nachgewiesen, daß in den untersuchten Cyanophyceen die Ribonukleinsäure in Granula lokalisiert ist, die im Cytoplasma gehäuft auftreten und in ihrem Aussehen und Verhalten den Paladeschen Granula oder Ribosomen vollkommen gleichen. Das Assimilationsprodukt der Cyanophyceen, ein Polyglukosid, liegt in Form größerer Granula zwischen den Lamellen des Chromatoplasmas.Herrn Professor Dr. H. Habs zu seinem 60. Geburtstag gewidmet.Der Verfasser dankt Frau M. Kasper für ihre wertvolle Mitarbeit.     

Die Wirkung von Uranylsalzen auf die Struktur des Bakteriennucleoids

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Der physikalische Status der Deoxyribonucleinsäure im Bakteriennucleoid

Subject of this paper is the physical and organization state of DNA within the nucleoid and its preservation during various treatments necessary for preparation of ultrathin sections of bacteria.Viscosimetric measurements show that the conformation of native DNA is not changed by treatment with osmium tetroxide or osmiumdichromate fixatives at pH 6 or 7. Neither has temporary complex formation with uranyl ions any effect. Storage at 22 C for 24 hours at pH 5.4 of the complex causes a 20% drop of viscosity, at pH 3.35 this drop is more pronounced. Denaturation of DNA by acid or heat seems to be slightly accelerated by the presence of uranyl ions.The conditions for denaturation and depolymerization of intracellular DNA were studied by electron microscopy of ultrathin sections of bacteria. The DNA resists denaturation unless its polynucleotide chains have been degraded to a certain extent. After artificial reduction of average chain length to a value which is in the range of nucleoid length, the conditions for denaturation of DNA within the nucloid are the same as for denaturation of thymus DNA in vitro. The morphological criterion of denaturation was a change in the arrangement of DNA fibres from an orderly pattern to a chaotic state.Uranyl ions do not cause visible denaturation of intracellular DNA in the absence of other deleterious influences, nor do they depolymerize intracellular DNA to such an extent that other agents may be able to cause rapid denaturation. Therefore uranyl treatment does not affect the physical and organizational state of intracellular DNA of bacteria.Contrary to uranyl ions cupric ions cause gross disorganization of nucleoid material.The results give strong support to the view that the bacterial nucleoid contains essentially one DNA molecule with helical conformation and almost uninterrupted polynucleotide chains.     

Refractive index of uranyl-treated bacterial cytoplasm as related to ribonucleic-acid content and growth rate

After fixation and treatment with uranyl acetate solutions, the refractive index (n _D) of the cytoplasm ofCorynebacterium bovis varies with substrate-dependent growth rate and RNA content. The effect, which presumably is due to quantitative binding of uranyl ions by RNA, permits a measurement of the growth rate of single cells in a single-species system by interference microscopy. Temperature-induced changes in growth rate are not reflected in changes ofn _D or RNA content.     

Microbiological basis of phosphate removal in the activated sludge process for the treatment of wastewater

Several strains resembling members of theAcinetobacter-Moraxella-Mima group of bacteria were isolated from activated sludge-type sewage treatment plants designed for phosphate removal. The bacteria are obligate aerobes but utilize as carbon and energy sources low-molecular intermediates generated anaerobically, particularly acetate and ethanol. These bacteria can be shown to be responsible for the phosphate luxury uptake occurring in these treatment plants. The bacteria are physiologically unusual in that they perform luxury uptake of phosphates in a complete growth medium. Phosphate release occurs on addition of a carbon source to the carbon-starved bacteria, lowering pH or both. The bacteria persist in the system by virtue of their ability to form floc.     

PHOSPHORUS CONTENT AND RATE OF GROWTH IN THE DIATOMS CYCLOTELLA NANA AND THALASSIOSIRA FLUVIATILIS

Cyclotella nana and Thalassiosira fluviatilis were grown in chemostat and turbidostat units in 1/3 strength artificial seawater supplemented with nutrients and vitamin B₁₂ in excess except for phosphorus (P) which in concentrations of 50 or 100 μg/liter was limiting. Different chemostat and turbidostat settings produced different cell numbers per unit volume which, since external P was practically nil, corresponded to varying amounts of bound P per cell. Growth rate plotted vs. P per cell follows a saturation curve. While no growth occurs at a certain minimum content of bound P, half the maxi-mum growth rate is observed at twice the minimum level of P,3/4 of the maximum at 3 times the minimum level, etc., the maximum growth rate being defined as that observed during growth unrestricted by P supply at a given set of conditions (light, temperature, salinity, etc.). Temperature and light were varied from 13.5 to 24 C and from 2000 to 6000 lux (continuous and intermittent). An abnormal growth curve was found with C. nana at 24 C and 6000 lux continuous light. Any change in P content of the cells significantly alters cell composition as reflected in P distribution in acid-soluble, lipid, and acid-insoluble fractions and in organic carbon content. External P does not immediately enter our equation for growth rate but is one of the factors deter-mining rate of P uptake and therefore bound P per cell. Conditions governing uptake, however, cannot be adequately controlled in a chemostat and there fore should be determined in a different experimental approach.