Interactions between marine bacteria and axenic diatoms (Cylindrotheca fusiformis, Nitzschia laevis, and Thalassiosira weissflogii) incubated under various conditions in the lab

Bacteria-phytoplankton interactions in aquatic systems range from symbiosis to parasitism and are h~ghly vanable in space and time. Three marine diatoms (Cylindrotheca fusiformis, Nitzschia laevis, and Thalassiosira weissflogi!) were grown in axenic culture and incubated under controlled lab conditions with single bacterial isolates, mixed bacterial populations, and seawater off Scripps Pier. Growth of both bacteria and algae was significantly higher when incubated together in f/2 medium or artificial seawater which were rich in inorganic nutrients, vitamins, and trace metals. In contrast, growth of diatoms in a vitamin and trace metal free medium was reduced or even negative when incubated together with bacterial isolates or seawater bacteria. In addition, the amount and quality of n v n n n l r r m o r i r m a t t o r i n r n i v o A n . l t a , m c u m r o A i f f o r o n t f r n m t h n c o n f n > > r o r > t l t ~~r o c I n n o n o r a l , -.-. , .z ---.--. ---. . .~