Release of macromolecular organic complexes by heterotrophic marine flagellates

Abstract

We examined whether or not the heterotrophic manne flagellate Paraphysomonas Imperforata releases macromolecular dissolved organic matter (DOM) 3H-bacterial prey (Vibrio spp ) were added to flagellate cultures and the accumulation of 3 ~-~~~ was measured Flagellates released a large amount of macromolecular DOM (6 to 57 % of 3 ~-~0 ~) that was nch in llpids (11pid macromolecular ratio = 0 20 0 92) One component of the macromolecular DOM was a digestive enzyme (acid phosphatase] of the flagellate The flagellate acld phosphatase was not degraded by proteases but it was suscephble to proteases after treatment with polymyxin B which destroys bacterial membranes These data suggest that bactenal membranes protected the released acid phosphatase from proteolyhc attack Ultracentnfugation showed that the sedimentation coefficient of the phosphatase was 15 to 42 S consistent with the hypothesis that the phosphatase IS part of a macromolecular complex We hypothesize that flagellates release thelr own digestive enzymes and incompletely digested membranes and probably other cellular components from bactenal prey and that these compounds form liposomehke organlc complexes These complexes may be important for understanding the chemical natuie and turnover of DOM in the oceans