Culturing of Amoeba proteus on Tetrahymena.
About: This article is published in Experimental Cell Research.The article was published on 1955-01-01. It has received 228 citations till now. The article focuses on the topics: Amoeba proteus & Amoeba (genus).
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TL;DR: In this article, the effect of crop (grass and grass-clover), N application rate (0, 40, 80, ) and manure type (no manure, farm yard manure and slurry) on the F/B ratio within three growing seasons was tested, as well as relations with soil and crop characteristics, nitrate leaching and partial N balance.
Abstract: It is frequently hypothesised that high soil fungal/bacterial ratios are indicative for more sustainable agricultural systems. Increased F/B ratios have been reported in extensively managed grasslands. To determine the shifts in fungal/bacterial biomass ratio as influenced by grassland management and to find relations with nitrogen leaching potential, we sampled a two-year-old field experiment at an organic experimental farm in the eastern part of The Netherlands. The effect of crop (grass and grass-clover), N application rate (0, 40, 80, ) and manure type (no manure, farm yard manure and slurry) on the F/B ratio within three growing seasons was tested, as well as relations with soil and crop characteristics, nitrate leaching and partial N balance. Biomass of fungi and bacteria was calculated after direct counts using epifluorescence microscopy. Fungal and bacterial biomass and the F/B ratio were higher in grass than in grass-clover. The F/B ratio decreased with increasing N application rate and multiple regression analysis revealed a negative relationship with pH. Bacterial activity (measured as incorporation of [3H]thymidine and [14C]leucine into bacterial DNA and proteins) showed the exact opposite: an increase with N application rate and pH. Leaching increased with N application rate and was higher in grass-clover than in grass. Partial N balance was more positive at a higher N application rate and showed an inverse relationship with fungal biomass and F/B ratio. We conclude that the fungal/bacterial biomass ratio quickly responded to changes in management. Grasslands with higher N input showed lower F/B ratios. Grass-clover had a smaller fungal biomass and higher N leaching than grass. In general, a higher fungal biomass indicated a lower nitrogen leaching and a more negative partial N balance (or smaller N surplus), but more observations are needed to confirm the relationship between F/B ratio and sustainability.
473 citations
Cites methods from "Culturing of Amoeba proteus on Tetr..."
...Twenty g soil and 95ml Prescott and James’s mineral salt solution (P&J medium, Prescott and James (1955)) were shaken by hand in a bottle for 30 s. Hundred ml of soil suspension was added to 20ml labelled thymidine and leucine in a 13ml polypropylene centrifuge tube with screw cap....
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TL;DR: It is suggested that a single mechanism underlies phagocytosis, pinocythesis, ropheocytotic, cytopempsis, and potocytoses in amebas.
Abstract: The attachment to the surface of the ameba (Chaos chaos L. (Pelomyxa carolinensis, Wilson)) of two proteins, ribonuclease and ferritin, and two colloidal suspensions, thorium dioxide and gold, was studied in the electron microscope. The initial step in the pinocytosis of ferritin and thorium dioxide particles by amebas is shown to be the attachment of these substances to the "hairlike" extensions of the plasmalemma. Ribonuclease caused alterations in the structure of the plasmalemma, but on account of its relative lack of density, it could not be definitely localized. Colloidal gold did not appear to be active with respect to pinocytosis in amebas. Since molecules in solution and particles in suspension are taken up by the same mechanism, the first step of which is their attachment to the cell surface, it is suggested that a single mechanism underlies phagocytosis, pinocytosis, ropheocytosis, cytopempsis, and potocytosis.
168 citations
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TL;DR: A mechanism for pinocytosis is suggested which relates adsorption of charged solutes on the plasmalemma to a decrease in the tension and the structural rigidity of the membrane.
164 citations
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TL;DR: Cell growth in volume and protein, and growth in the volume of the nucleus were followed over the cell cycle employing small groups of amoebae in synchronous growth, and nuclear growth is rapid following division but falls to a lower rate during most of the interphase.
153 citations
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TL;DR: The results suggest that many functions of soil biota that are well established in permanent grassland, are restored in a ley-arable crop rotation, however, due to a reduction in certain species, specific functions of these soilBiota could be reduced or lost.
152 citations
Cites methods from "Culturing of Amoeba proteus on Tetr..."
...20 g soil and 95 ml Prescott and James’s mineral salt solution (P&J medium, Prescott and James, 1955) were shaken by hand in a bottle for 30 s. 100 ml of soil suspension was added to 20 ml labelled thymidine and leucine in a 13 ml polypropylene centrifuge tube with screw cap....
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