Thursday, February 21, 2008

Seaweed linked to parasites

A brief article on the Herald's website heralds the discovery of a type of brown algae whose closed relatives include a couple of parasites, cryptosporidium and plasmodium.
This is the closest yet to linking those parasites to algae.

The link is already understood in general terms, because the parasites contain relics of chloroplasts, the mechanism for photosynthesising sunlight into energy. The parasites thus evolved from feeding off sunlight to feeding directly off hosts, leaving residual traces of their origins.

Previously, the closest link between those parasites and algae was a group of dinoflagellates (some parasitic simple algae); this discovery brings the link much closer.

The resonance with Sydney is that they were found in Sydney harbour, while seeking algae living in coral.

Brown algae tends to manifest as seaweed.

Cryptosporidium and plasmodium are both single-cell eukaryotes of the phylum Apicomplexa (classes Aconoidasida and Conoidasida respectively - differing in the absence/presence of the conoid, an organelle comprised of a "funnel of rods").

Brown algae are distinguished by chloroplasts with four membranes, suggesting an origin in symbiosis between two eukaryotes. While Brown algae, dinoflagellates and those parasites are all eukaryotes, in the kingdom chromalveolata. Brown algae are multicellular; the parasites are unicellular, and dinoflagellates are... _mostly_ unicellular.

The online report raises more questions than answers. It refers to the print edition, but it's not been published there. What is the name of this new algae? Which dinoflagellates? The findings are said to be published in Nature, but maybe the paper hasn't been published yet, because a search of Nature's archive doesn't turn it up.

And finally... hello to Dee Carter, microbiology Associate Professor at Sydney University, quoted in the report. Based on this photo (not so much the current one at the university!), looks like the same Dee Carter who was in my class at school (Onslow College). Small world.

Other references: Wikipedia [beware, however, there are inconsistencies in classifying organisms: some use unhelpful paraphyletic groupings such as protista.]

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