Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Organic Geochemistry Group, MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Str. 8, 28359 Bremen, Germany.
FEMS Microbiol Ecol. 2018 Jan 1;94(1). doi: 10.1093/femsec/fix131.
Germination of akinetes of filamentous heterocyst-forming cyanobacteria of the order Nostocales is an essential process that ensures survival and recolonization after long periods of unfavorable conditions, as desiccation, cold and low light. We studied the morphological, physiological and metabolic changes that occur during germination of akinetes in two model species of cell differentiation, Anabaena variabilis ATCC 29413 and Nostoc punctiforme ATCC 29133, which live in different habitats. We characterized the akinete envelopes and showed their similarity to envelopes of N2-fixing heterocysts. Akinete germination started inside the envelopes and was dependent on light intensity but independent of nitrogen supply. During the germination of A. variabilis akinetes, cell division and heterocyst differentiation were highly accelerated. The energy for cell division was initially supplied by respiration of glycogen and subsequently by photosynthesis. By contrast, during germination of N. punctiforme akinetes, cell division and heterocyst differentiation were slow. During the initial 15-20 h, N. punctiforme akinetes increased in volume and some burst. Only then did intact akinetes start to divide and fully germinate, possibly fueled by nutrients released from dead akinetes. The different strategies used by these different cyanobacteria allow successful germination of dormant cells and recolonization under favorable conditions.
类囊体丝状异形胞形成蓝藻目异形胞的萌发是一个必要的过程，确保了在长时间的不利条件下，如干燥、寒冷和低光照下的生存和再殖民化。我们研究了两个细胞分化模型种——变鱼腥藻 ATCC 29413 和点形念珠藻 ATCC 29133 中异形胞萌发过程中发生的形态、生理和代谢变化，它们生活在不同的栖息地。我们对异形胞包被进行了表征，并表明它们与固氮异形胞的包被相似。异形胞的萌发始于包被内部，并且依赖于光强，但与氮供应无关。在变鱼腥藻异形胞的萌发过程中，细胞分裂和异形胞分化被高度加速。细胞分裂的能量最初由糖原的呼吸提供，随后由光合作用提供。相比之下，在点形念珠藻异形胞的萌发过程中，细胞分裂和异形胞分化较慢。在最初的 15-20 小时内，点形念珠藻异形胞体积增加并有些破裂。只有那时，完整的异形胞才开始分裂并完全萌发，可能是由死异形胞释放的营养物质提供燃料。这些不同的蓝藻使用的不同策略允许休眠细胞成功萌发，并在有利条件下重新殖民化。
