Monday, June 11, 2007

Kleptoplasty


Kleptoplasty is a wonderful term. It is used to describe the behavior of a group of organisms that are able to ingest algal cells and degrade the cells, but not the chloroplasts contained within the cells. The chloroplasts remain functional for some period of time during which the photosynthetic products generated by the sequestered chloroplasts are utilized by the new 'host'.

On the left is a figure from a paper by Gast et al. in the journal Enviornmental Microbiology from earlier this year showing a kleptoplastic dinoflagellate isolated from the Ross Sea in Antartica (the paper is in a free issue of the journal so go read the whole thing).

In addition to being a very interesting behavior from an ecological perspective, kleptoplasty is of evolutionary interest because the capacity to grow autotrophically by photosynthesis arose within dinoflagellates by the retention of chloroplasts from ingested algal cells. This ability appears to have arisen multiple times within dinoflagellates because not all contain chloroplasts from the same type of algal cell.

2 comments:

César Sánchez said...

Kleptoplasty (say it aloud, sounds funny!) is a very interesting phenomenon. I'm wondering to which degree this may happen with other organelles or cell structures: a microorganism eating another microbe but not degrading its mitochondria... or even its nucleus! (ok, perhaps the nucleus is too fragile in a digestion process because of all those pores in its envelope...)

amstar said...

yes it is a fun word.

I don't know if anyone has looked at the mitochondria of kleptoplastic organisms. It would be pretty easy to do. Take the paper I linked to in the post. All they'd need to do in that system is to look to see if the dinoflagellates are harboring haptophyte-like mitochondria that could have come from the same source as the chloroplasts they sequester.

The amount of genetic material in these cells is interesting. If you count both mitochondirial chromosomes, the chloroplast chromosome and both nuclei, there is at least the potential for a cell to contain 5 distinct genomes.

As for other cells structures, some mixotrophic cilliates prey on phototrophs that have eye-spots. After ingesting the cells, the cilliates utilize both the chloroplasts and the eye-spots.