Fourier transform infrared spectroscopy as a novel tool to investigate changes in intracellular macromolecular pools in the marine microalga Chaetoceros muellerii (Bacillariophyceae)

Fourier Transform Infrared (FT-IR) spectroscopy was used to study carbon al location patterns ill response to changes in nitrogen availability in the d iatom Chaetoceros muellerii Lemmerman, The results of the FT-ER measurement s were compared with those obtained with traditional chemical methods. The data obtained with both FT-IR and chemical methods showed that nitrogen sta rvation led to the disappearance of the differences in cell constituents an d growth rates existing between cells cultured at either high [NO3 ] or hig h [NH4+]. Irrespective of the nitrogen source supplied before nitrogen star vation, a diversion of carbon away from protein, chlorophyll, and carbohydr ates into lipids was observed. Under these conditions, cells that had previ ously received nitrogen as nitrate appeared to allocate a larger amount of mobilized carbon into lipids than cells that had been cultured in the prese nce of ammonia, All these changes were reversed by resupplying the cultures with nitrogen, The rate of protein accumulation in the N-replete cells was slower than the rate of decrease under nitrogen starvation. This study dem onstrates that the relative proportions of the major macromolecules contain ed in microalgal cells and their changes in response to external stimuli ca n be determined rapidly, simultaneously, and inexpensively using FT-IR, The technique proved to be equally reliable to and less labor intensive than m ore traditional chemical methods.