Analysis of Common Enzymatic Pathways in Gambierdiscus toxicus and Symbiodinium in the TCA Cycle :: The TCA Cycle

Background: Dinoflagellates are one of the four main types of phytoplankton, which are photosynthetic, single celled and free living organisms in the ocean. Dinoflagellates cause the Harmful Algal Blooms (HAB) also known as the red tide effect (Hackett et al 2004). Toxicity persisting at upper levels of the food chain is detected in them from the ones which are toxic, but not all such blooms are toxic. Enhanced detection capabilities may in part contribute to observed high frequency and severity of toxic blooms. As they are also important in the health of coral reefs their study has gained significant interest. Species are often selected for genome sequencing based on their importance as a model organism or relevance to human health, such as the HAB case. Fig 1 Gambierdiscus Toxicus and its golden brown chloroplasts (Image courtesy: Institute Malarde) Recreating the evolutionary history of dinoflagellates has been challenging as they possess a known ability to transform from noncyst – to cyst – forming strategies (unreferenced/Wikipedia). The dinoflagellate nucleus lacks histones, nucleosomes and maintains continually condensed chromosomes during mitosis (Dodge 1966), making their classification difficult (Hackett et al 2004). Though being classified as eukaryotes, the dinoflagellate nuclei are not characteristically eukaryotic (Dodge 1966). However, typical eukaryotic organelles, such as Golgi bodies, mitochondria and chloroplasts are present in dinoflagellates (Morrill et al 1983). Since dinoflagellate nuclei possess intermediate characteristics between the coiled DNA areas of prokaryotic bacteria and the well-defined eukaryotic nucleus it was termed ‘mesokaryotic’ by Dodge (1966). This research focuses on Gambierdiscus toxicus which is an armored, marine, benthic species in the phylum Dinoflagellata. It has an epitheca and a hypotheca, that is very similar in size, compressed anterio-posteriorly. The theca is covered with numerous deep and dense pores which are very thick. This species is autotrophic creating energy via several golden-brown chloroplasts (Hackett et al 2004), but is also heterotrophic and hence is referred to as mixotrophic. It has a ventrally – oriented crescent shaped nucleus. (Adachi & Fukuyo 1979). It usually inhabits warmer waters such as bay, mediterranian, tropical/sub – tropical in North/Central America (Shiumuzu et al 1982; Loeblich & Indelicato 1986), Asia/Pacific (Holmes & Tao 2002; Lu & Hodgkiss 2004) and has recently been identified in the Mediterranean (Aligizaki & Nikolaidis 2008). These authors identified the organisms to genus level, at best of their effort, so may have been one of the less common members of its g enus although it is unlikely.