Abstract To evaluate the influences of cyanobacterial extracellular polymeric substances (EPS) on CaCO3 precipitation, calcification experiments were conducted for 48 h (initial values of calcite saturation state and equilibrium CO2 partial pressure were ∼5-fold and ∼600 μatm, respectively) using cultures of four filamentous strains (Leptolyngbya sp. (NIES-2104), Scytonema sp. (NIES-2130), Phormidium ambiguum (NIES-2119), and Spirulina subsalsa (NIES-598)). All cultures induced CaCO3 precipitation mainly by photosynthesis to form mono-/ poly crystalline calcite and amorphous calcium carbonate (ACC) around them. These features suggested a CaCO3 nucleation process via an ACC precursor phase on negatively charged substances generated by cyanobacteria (i.e., cell walls, EPS, and oxygen bubbles). The characteristics of the precipitated CaCO3 were strongly influenced by the surface properties of the cyanobacteria. For Leptolyngbya, which lacks EPS, a small number of CaCO3 was nucleated onto the smooth surface of negatively charged cell walls and entire cells were incorporated into a large single crystal of calcite. For Scytonema and Phormidium, which possess EPS sheaths, a relatively large number of CaCO3 was nucleated onto the rough surface of negatively charged sheaths, and their sheaths were encrusted and partially impregnated by calcite crystals. For Spirulina, which possesses a loose EPS matrix, CaCO3 nucleation was scarce and restricted to the surface of negatively charged oxygen bubbles stabilized by the EPS matrix to form hollow calcite crystals. These results suggest that chemical properties (i.e., abundance of dissociated acidic groups) primarily controlled the presence/absence of CaCO3 nucleation around cyanobacteria, while a physical property (i.e., submicron-scale structure of negatively charged substances) primarily controlled the numbers of crystal nuclei provided and stabilized ACC precursors as well as the calcification styles (sheath encrustation or impregnation).

中文翻译：

---

在蓝藻周围成核的 CaCO3 的特征：对钙化过程的影响

摘要 为了评估蓝藻细胞外聚合物 (EPS) 对 CaCO3 沉淀的影响，使用培养物进行了 48 小时的钙化实验（方解石饱和状态和平衡 CO2 分压的初始值分别为~5 倍和~600 μatm）。四种丝状菌株（Leptolyngbya sp. (NIES-2104)、Scytonema sp. (NIES-2130)、Phormidium ambiguum (NIES-2119) 和 Spirulina subsalsa (NIES-598)）。所有培养物主要通过光合作用诱导 CaCO3 沉淀，在它们周围形成单晶/多晶方解石和无定形碳酸钙 (ACC)。这些特征表明在蓝藻产生的带负电荷的物质（即细胞壁、EPS 和氧气泡）上通过 ACC 前体相进行 CaCO3 成核过程。沉淀的 CaCO3 的特性受蓝藻表面性质的强烈影响。对于缺乏 EPS 的 Leptolyngbya，少量 CaCO3 在带负电的细胞壁的光滑表面成核，整个细胞被纳入方解石的大单晶中。对于具有EPS鞘的Scytonema和Phormidium，相对大量的CaCO3在带负电荷的鞘的粗糙表面上成核，并且它们的鞘被方解石晶体包裹并部分浸渍。对于具有松散 EPS 基质的螺旋藻，CaCO3 成核很少，并且仅限于由 EPS 基质稳定的带负电荷的氧气泡表面，形成空心方解石晶体。这些结果表明化学性质（即