Symbiont-driven sulfur crystal formation in a thiotrophic symbiosis from deep-sea hydrocarbon seeps.
Bottom Line: This suggests that their formation is either extra- or intracellular in symbionts.We propose that formation of these crystals provides both energy-storage compounds for the symbionts and serves the symbiosis by removing excess toxic sulfide from host tissues.This symbiont-mediated sulfide detoxification may have been crucial for the establishment of thiotrophic symbiosis and continues to remain an important function of the symbionts.
Affiliation: Department of Limnology and Oceanography, Faculty of Life Sciences, University of Vienna, Althanstr. 14, 1090, Vienna, Austria.Show MeSH
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Mentions: Viable symbionts, characterized by intact outer and cytoplasmic membranes and a moderately electron-dense cytoplasm containing glycogen and chromatin strands, contained small, membrane-bound, electron-translucent sulfur vesicles with S8 sulfur (Eichinger et al., 2011). The first step in the transition for sulfur vesicles inside the symbionts to accumulation of crystals in host cell cytoplasm is the disintegration of the sulfur vesicle membrane. Such remnants of sulfur vesicles were present as diffuse electron-translucent patches within the symbiont's cytoplasm (Fig. 7A). Next, the remnants of the sulfur vesicles must pass through the symbiont's cell wall and the symbiosome membrane into the bacteriocyte cytoplasm (Fig. 7B). Here sulfur accumulates, which was visible as conspicuous, electron-translucent area often with straight edges typical of the crystals (Fig. 7C). Such areas were completely surrounded by symbionts with intact cell walls, except where they were adjacent to the crystals. Crystals are then found in bacteriocytes with an intact nucleus and cell membranes.
Affiliation: Department of Limnology and Oceanography, Faculty of Life Sciences, University of Vienna, Althanstr. 14, 1090, Vienna, Austria.