Cyanobacteria are abundant in nearly every surface environment on Earth. Understanding their chemical reactivity and metal binding capacity with varying ionic strength (IS) is paramount to understanding trace metal cycling in natural environments. We conducted an investigation on the cell surface reactivity of the freshwater cyanobacterium Synechocystis sp. PCC 6803 at freshwater (0.01 M NaCl) and marine (0.56 M NaCl) IS. Potentiometric titration data were used to develop a multiple discrete site, non-electrostatic surface complexation model (SCM), and corresponding cell surface functional group identities were verified using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Synechocystis cells were best modeled in FITEQL 4.0 using a non-electrostatic 2-site protonation model. Cadmium (Cd) adsorption experiments paired with SCM was utilized to calculate the binding constants of Cd. Synechocystis surface functional groups demonstrated a stronger affinity for Cd across the entire pH range studied (3–9) at freshwater IS, with the greatest difference at circumneutral pH (6–8) where Cd adsorption in freshwater IS was 60% greater than at marine IS. These data combined with the ubiquitous distribution of Synechocystis in freshwater and brackish environments suggest that these organisms could play an important role in trace metal cycling in environments with large salinity gradients, such as estuaries and deltas, and could act as a transport mechanism for trace metals from terrestrial to marine settings.

蓝细菌在地球上几乎每个表面环境中都丰富。了解其化学反应性和具有不同离子强度（IS）的金属结合能力对于了解自然环境中的痕量金属循环至关重要。我们进行了淡水蓝藻Synechocystis sp。的细胞表面反应性的调查。淡水（0.01 M NaCl）和海洋（0.56 M NaCl）的PCC 6803 IS。电位滴定数据用于建立多个离散位点，非静电表面络合模型（SCM），并使用衰减全反射傅里叶变换红外光谱（ATR-FTIR）光谱法验证了相应的细胞表面官能团身份。突囊藻在FITEQL 4.0中，最好使用非静电2位质子化模型对细胞进行建模。镉（Cd）吸附实验与SCM配对用于计算Cd的结合常数。囊藻表面官能团在淡水IS的整个pH范围内（3-9）表现出对Cd的更强亲和力，在环境pH值（6-8）时最大差异，其中淡水IS中的Cd吸附比海洋中的镉高60％。是。这些数据结合到处都是集胞藻 在淡水和微咸的环境中，这些生物可能在盐度梯度较大的环境（例如河口和三角洲）中的痕量金属循环中发挥重要作用，并可能充当痕量金属从陆地到海洋环境的运输机制。