THE TOXIC DINOFLAGELLATE PROROCENTRUM-LIMA AND ITS ASSOCIATED BACTERIA .1. AN ULTRASTRUCTURAL-STUDY

Prorocentrum lima Ehrenberg (Dodge) and its associated bacteria were e xamined by scanning and transmission electron microscopy. The absence of trichocysts in this species is confirmed. The peculiarities of this P. lima strain (PL2V) were an abundance of intracellular reserves and extensive development of fibrous bodies, probably constituting a part of the pusule. Associated bacterial microflora was abundant. Various morphological types of free-living bacteria were found free-floating i n the liquid culture medium. Numerous bacteria were directly attached to the dinoflagellate cell or agglomerated, forming large aggregates i n the P. lima mucus. Bacteria-like inclusions were visible in a few pe rcent of the P. lima cells observed. We suggest that they were intrace llular bacteria, and that bacterial infection within this toxic dinofl agellate is possible, but occurs only rarely. This SEM and TEM study p rovides the first evidence for an association between this toxic dinof lagellate and surrounding bacteria.