| Abstract: | The mineralized envelope surrounding the trachelomonad cell is a complex of organic and inorganic components, anastomosed to form a structure that is characteristic of the species. Although there may be considerable morphological variability in envelope size, shape and ornamentation, its microarchitecture is characterized by two basic components: granular and needle-like deposits. The present study documents for the first time that manipulation of the culture conditions results in predictable changes in envelope ultrastructure, color and elemental composition. Supplemental iron (Fe) in the culture medium results in an increase of granular components in the envelope, whereas supplemental managanese (Mn) results in an increase of needle-like components; with nitrogen (N) supplements there is an increase of both granular and needle-like components in the envelope. It is also shown here that autoxidation of Fe may occur, resulting in the accumulation of Fe deposits along strands of unmineralized envelope mucilage. Autoxidation and deposition of Mn do not occur. |
