| Copper (Cu), one of about seven essential metals used by photoautotrophs, is a limiting resource in some parts of the ocean because of its low and variable concentration. This thesis examined copper dependence of growth, Cu uptake and quotas of diatoms of the Thalassiosirales isolated from different ocean habitats. A major finding of the research was that Cu quotas of diatoms of the Thalassiosirales are dependent on the type of photosynthetic electron transport gene they contain viz. plastocyanin; encoding a Cu-dependent protein versus cytochrome c6; encoding a Fe-dependent protein. Increased Cu quotas of plastocyanin-containing species reduced the growth rates they attained in Cu-deplete seawater. Cytochrome c6-containing species required lower Cu concentrations to achieve maximum rates of growth and contained less cellular Cu than plastocyanin-containing species. Steady state uptake rate of Cu by T. oceanica (a plastocyanin-containing species) was a linear function of growth irradiance at low and high Cu concentration, suggesting that Cu uptake was light dependent. In Cu-deplete seawater, high light abolished the Cu-limited phenotype of this species by enabling it to acquire sufficient Cu for maximum growth. |
