Products of photosynthesis by marine phytoplankton: Chitin in TCA “protein” precipitates

Evidence is presented which documents probable errors in previous estimates of 14CO 2 incorporation and cellular distribution in estuarine and marine phytoplankton. Extension of the standard extraction procedure for phytoplankton photosynthetic carbon pools shows the presence of chitin (poly N- acetyl- d-glucosamine ) in the previously considered protein pool. Trichloracetic acid (TCA) precipitates were processed in several ways including alkali extraction (protein solubilization), 4 and 6 N HC1 hydrolysis, hydrolysis with purified chitinase coupled with HPLC and colorimetric analysis of amino sugars. Data for Thalassiosira pseudonana cultures and natural photoplankton populations are presented. The results show the presence of diatom chitin (chitan) in the TCA precipitate which has been previously characterized solely as the “protei” fraction.