The ultrastructure of cells and cellulose membranes in Acrasiae

Gezelius, Kerstin

doi:10.1016/0014-4827(59)90310-6

Cited by 57 publications

(25 citation statements)

References 45 publications

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“…Esterosomes were shown to contain mainly two proteins, crystal protein and D2. Consistent with several previously published studies of developing cells [1][2][3] and spores [4], the crystals we observed in vegetative cells were without obvious membranes ( Figure 1), while other studies of aggregating cells showed crystalline bodies with membranes [5,6]. This difference may have been a consequence of the different protocols used for preparing the samples for microscopy.…”

Section: Localization Of Gp70supporting

confidence: 92%

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Role of Esterase gp70 and Its Influence on Growth and Development of Dictyostelium discoideum

Yuan

Chia

2000

Experimental Cell Research

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Gp70 is an esterase originally called crystal protein because of its presence in crystalline structures in aggregation-competent Dictyostelium discoideum cells. Although postulated to break down spore coats, the function of gp70 in vivo was incompletely investigated. Our immunolocalization and biochemical studies of vegetative D. discoideum amoebae show that gp70 was recruited to phagosomes and found in lysosomes. Purified gp70 was effective at hydrolyzing naphthyl substrates with acyl chains typical of lipids and lipopolysaccharides, indicating that the gp70 was involved in digesting endocytosed molecules. The activity of purified gp70 was inhibited by reductants that retarded its electrophoretic mobility and verified the presence of intramolecular disulfide bonds predicted by its amino acid sequence. Compared to wild-type cells, cells overexpressing gp70 were more phagocytically active, had shorter generation times, and produced more fruiting bodies per unit area, while cells lacking gp70 were phagocytically less active with longer doubling times, developed more slowly, and had significantly fewer fruiting bodies per unit area. Consistent with the phenotype of a disrupted metabolism, one-third of the gp70-minus cells were large and multinucleated. Together, these results indicated that despite its crystalline appearance, gp70 was an active esterase involved in both the growth and the development of D. discoideum.

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Section: Localization Of Gp70supporting

confidence: 92%

“…By electron microscopy, crystalline bodies are observed in amoebae of the cellular slime mold Dictyostelium discoideum [1,2]. The crystal structures become more numerous between the growth and aggregation stages, are present in mature spores, and disappear only after spore germination [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Role of Esterase gp70 and Its Influence on Growth and Development of Dictyostelium discoideum

Yuan

Chia

2000

Experimental Cell Research

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“…MLBs are not produced only by higher eukaryotic cells, as they have also been observed in protozoa and, more particularly, in Dictyostelium discoideum (2)(3)(4)(5)(6)(7)(8)(9)(10). D. discoideum is a soil amoeba and a bacterial predator that internalizes its prey through phagocytosis.…”

mentioning

confidence: 99%

“…discoideum cells secrete their MLBs, and this phenomenon has been repeatedly seen at different steps of the multicellular process (2,(4)(5)(6)(7)(8). Despite the fact that bacterial lawns best mimic the natural environment of D. discoideum, the secretion of MLBs by vegetative cells grown on a bacterial lawn has been reported only once to our knowledge, with few details (10).…”

mentioning

confidence: 99%

“…Despite the fact that bacterial lawns best mimic the natural environment of D. discoideum, the secretion of MLBs by vegetative cells grown on a bacterial lawn has been reported only once to our knowledge, with few details (10). This is probably due to the fact that the secretion of MLBs observed in most studies occurred under conditions where cell aggregation was induced by starvation or where vegetative cells could not be distinguished from starved cells (2,(4)(5)(6)(7)(8).…”

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Lipid Composition of Multilamellar Bodies Secreted by Dictyostelium discoideum Reveals Their Amoebal Origin

et al. 2013

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When they are fed with bacteria, Dictyostelium discoideum amoebae produce and secrete multilamellar bodies (MLBs), which are composed of membranous material. It has been proposed that MLBs are a waste disposal system that allows D. discoideum to eliminate undigested bacterial remains. However, the real function of MLBs remains unknown. Determination of the biochemical composition of MLBs, especially lipids, represents a way to gain information about the role of these structures. To allow these analyses, a protocol involving various centrifugation procedures has been developed to purify secreted MLBs from amoeba-bacterium cocultures. The purity of the MLB preparation was confirmed by transmission electron microscopy and by immunofluorescence using H36, an antibody that binds to MLBs. The lipid and fatty acid compositions of pure MLBs were then analyzed by high-performance thin-layer chromatography (HPTLC) and gas chromatography (GC), respectively, and compared to those of amoebae as well as bacteria used as a food source. While the bacteria were devoid of phosphatidylcholine (PC) and phosphatidylinositol (PI), these two polar lipid species were major classes of lipids in MLBs and amoebae. Similarly, the fatty acid composition of MLBs and amoebae was characterized by the presence of polyunsaturated fatty acids, while cyclic fatty acids were found only in bacteria. These results strongly suggest that the lipids constituting the MLBs originate from the amoebal metabolism rather than from undigested bacterial membranes. This opens the possibility that MLBs, instead of being a waste disposal system, have unsuspected roles in D. discoideum physiology.

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Electron microscopy of Wallerian degeneration

Lee

1963

J of Comparative Neurology

112

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The ultrastructure of cells and cellulose membranes in Acrasiae

Cited by 57 publications

References 45 publications

Role of Esterase gp70 and Its Influence on Growth and Development of Dictyostelium discoideum

Role of Esterase gp70 and Its Influence on Growth and Development of Dictyostelium discoideum

Lipid Composition of Multilamellar Bodies Secreted by Dictyostelium discoideum Reveals Their Amoebal Origin

Electron microscopy of Wallerian degeneration

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