Wirtskreis und Infektionscyclus eines neu isolierten Bdellovibrio bacteriovorus-Stammes

Zusammenfassung Der neu isolierte Stamm W von Bdellovibio bacteriovorus infiziert und lysiert Rhodospirillum rubrum F und alle anderen untersuchten Athiorhodaceae, nicht aber Pseudomonas aeruginosa und Spirillum serpens. Er befällt auch zahlreiche Enterobacteriaceae und von den grampositiven Bakterien Streptococcus faecalis und Lactobacillus plantarum.Nach dem Festheften an der Zellwand wird diese in 3–20 min durchdrungen. In 10–60 min ist Bdellovibrio vollständig in die Zelle eingedrungen und hat sich im Raum zwischen Zellwand und cytoplasmatischer Membran angesiedelt.In 3–5 Std wird der gesamte Zellinhalt bis auf die Membranen aufgelöst. In dieser Phase erfolgt die Vermehrung von Bdellovibrio. In den ghosts sind die Parasiten in lebhafter Bewegung. Die Geißel hat einen Gesamtdurchmesser von 29 m und eine Länge von etwa 3 . Sie ist von einer Geißelscheide umgeben, die in Verbindung zur Zellwand steht. Der Durchmesser der Geißel ohne Scheide beträgt etwa 18 m. Bdellovibrio kann oberhalb eines Sauerstoffpartialdruckes von 4–5 mm Hg infizieren und sich vermehren. Der Titer von Bdellovibrio nimmt bei Aufbewahrung in lysierten Kulturen in 36 Tagen von 10⁸ auf 10¹ pfu (plaque forming units) je ml ab. Bei Aufbewahrung in Nährkultur sinkt der Titer nur auf 10⁴ pfu/ml ab. Die Zahl der Plaques im Verhältnis zum Titer der Impfsuspension von Bdellovibrio schwankt in Abhängigkeit vom Wirtsstamm. Wenn man die Plaque-Bildungsrate bei R. rubrum gleich 1 setzt, beträgt sie bei Serratia marcescens 0,0001, bei Proteus vulgaris 10. Bd. bacteriovorus, Stamm W wächst nicht in synthetischer Nährlösung oder Lysaten. Ein geringes Wachstum ohne Zellteilung findet in Zellextrakten von R. rubrum statt. Der Stamm vermehrt sich jedoch in hitzeinaktiviertem R. rubrum. Die Plaque-Bildungsrate ist unter diesen Bedingungen aber sehr niedrig.In Lysaten treten encystierte Dauerformen von Bdellovibrio bacteriovorus auf.

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The host range and the infectious cycle of a new isolated, on gram-positive and gram-negative bacteria parasiting Bdellovibrio bacteriovorus strain

Summary Rhodospirillum rubrum and all other investigated Athiorhodaceae are infected and lysed by the new isolated strain W of Bdellovibrio bacteriovorus. This strain W parasites on numerous Enterobacteriaceae and the gram-positive bacteria Streptococcus faecalis and Lactobacillus plantarum, but not on Pseudomonas aeruginosa and Spirillum serpens.After attachment of Bdellovibrio to the host, the cell wall is penetrated in 3 to 20 min. In 10 to 60 min Bdellovibrio has completely entered the host cell. He remains in the space between cell wall and cytoplasmic membrane of the host.The host cell is completely lysed within 3 to 5 hours. During this phase the size and cell number of Bdellovibrio are increased and a new flagellum is likely to be formed. In the ghosts of the host cell a strong movement is observed. The single polar flagellum of Bdellovibrio has a diameter of 29 m. The flagellum consists of an inner core ( 18 m) and an outer sheath which is continued into the cell wall. Bdellovibrio is able to grow and to infect only under aerobic or semiaerobic conditions (oxygen partial pressure 4 to 5 mm Hg and more). The titer of Bdellovibrio is gradually decreased from 10⁸ to 10¹ plaque forming units (pfu) per ml, when kept in the lysate for 36 days. In a synthetic medium there is a diminution of 10⁴ pfu/ml only. The plating efficiency is dependent of the host strain. If the plating efficiency of Bdellovibrio with Rhodospirillum rubrum is 1.0, the rate varies from 0.0001 with Serratia marcescens to 10 with Proteus vulgaris. Bdellovibrio bacteriovorus strain W does not grow in a synthetic medium. However, it grows but does not multiply in cell free extracts of Rhodospirillum rubrum. The parasite is also able to infect and lyse heat inactivated R. rubrum. But the plating efficiency in this case is very low.It has been observed that in lysed cells of R. rubrum certain amount of Bdellovibrio is encysted. The morphology and fine structure of these cells is quite different from the normal virulent type.

     

Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q₁₀ of threshold current was 2.3 (SD = 0.2), while the Q₁₀ for threshold potentials was 2.0 (SD = 0.1).     

Modification of the zona-free hamster ova bioassay of boar sperm fertility and correlation with in vivo fertility

These studies were designed to evaluate the ability of the zona-free hamster ova bioassay to detect differences in fertility of boar sperm. In the first study, sperm from two previously infertile boars were compared to sperm from seven previously fertile boars. The percentage of zona-free hamster ova penetrated by sperm from the previously infertile boars was significantly lower than the percentage of ova penetrated by sperm from previously fertile boars (18% of ova penetrated vs. 83%, P < .001). In the 14 ejaculates from the previously infertile boars that had ejaculate motilities of 50% or greater, the percentage of zona-free hamster ova penetrated continued to be lower than in ejaculates from the fertile boars. One of the two previously infertile boars consistently had a normal semen analysis. The only two observed manifestations of his reduced fertility were his zero conception rate and the limited ability of his sperm to penetrate zona-free hamster ova. In the second study, females were inseminated with equal numbers of sperm from two previously fertile males and the paternity of offspring determined at birth. The experiment was replicated with four combinations of six boars. A high correlation was observed between the percentage of offspring sired and the ability to penetrate zona-free hamster ova (R = .89). Neither morphology nor the ability of the sperm to undergo an acrosome reaction during in vitro incubation was correlated with fertility in the competitive mating situation. These results suggest the zona-free hamster ova bioassay can improve the in vitro fertility assessment of fresh boar semen.