Use of high temperature catalytic oxidation (HTCO) to measure carbon content of microorganisms

High temperature catalytic oxidation (HTCO) was used for the first time to determine carbon content of heterotrophic protists (the helioflagellate Pte ridomonas danica, the dinoflagellate Oxyrrhis marina, and the scuticociliat e Uronema sp.) and bacteria (Escherichia coli). This technique has the adva ntage, over the conventional CHN analysis of glass-fiber filters, of measur ing total organic carbon in the liquid phase. Failing to retain small organ isms on filters and cell rupture during filtration can thus be avoided. Cel l volumes were measured on live (Coulter Counter) and Lugol's iodine- or fo rmaldehyde-preserved cells and used to obtain a carbon:biovolume conversion factor for each species. Carbon:biovolume conversion factors ranged from 1 23 to 175 and from 121 to 864 fg C mu m(-3) for live and preserved cells, r espectively. A linear regression of cell carbon content versus live biovolu me gave a mean carbon:biovolume conversion factor of 125.3 +/- 7.6 (SE) fg C mu m(-3) for the 4 species studied with biovolumes ranging from 0.69 to 1 590 mu m(3) The data obtained in this study is compared to live and preserv ed cells data obtained from the literature and the possibility of using a s ingle carbon:biovolume conversion factor for bacteria and protozoa is discu ssed.