3.6 Cell morphology
SEM images showed that the algal cells only weakly interacted with 200 mg/L Mt (Fig. 6A&B). At Mt500, Mt particles were more tightly adsorbed by the cells (Fig. 6C). In addition, abundant fibrous Pal particles were adhered to the cell surface at Pal200 (Fig. 6D&E). With the gradual elevation of Pal concentration, the density of mineral particles on the cell surface gradually increased. At Pal500, the cells were almost wrapped in Pal (Fig. 6F), suggesting strong binding between the Pal and algal cells.
TEM observations showed that, Mt crystals were adsorbed onto the cells at Mt200 (Fig. 7A). With the increase of Mt addition, more Mt particles were observed on the cell surface (Fig. 7B). In addition, there were only scarce mineral particles around the cell wall at Pal200, which appeared as separated mineral fibers (Fig. 7C). The Pal particles even inserted into the cell wall due to its fibrous shape. Compared with Mt, cell lysis could be observed with large amounts of Pal adsorbed on the cell surface at Pal500 (Fig. 7D).