Filasterea

Ministeria vibrans

Ministeria vibrans

Filasterea is a clade originally proposed by Shalchian-Tabrizi et al. in 2008 based on a phylogenomic analysis with dozens of genes. Filasterea was found to be the sister-group to the clade composed of Metazoa and Choanoflagellata within the Opisthokonta, a finding that has been further corroborated with additional, more taxon-rich, phylogenetic analyses (Torruella et al. 2012, Torruella et al. 2015). Filasterea comprises, so far, only two described genus: Capsaspora and Ministeria spp. . The name (latin filum: thread; greek. aster: star) indicates the main morphological features shared by all their integrants, that is a small, rounded, amoeboid uninucleated cellular body covered in long and radiating cell protrusions known as filopodia. These filopodia may be involved in substrate adhesion and capture of prey.

Caspaspora owczarzaki

Capsaspora owczarzaki

There are currently cultures from two filasterean species: Capsaspora owczarzaki and Ministeria vibrans, the first isolated from within a fresh-water snail, the second a marine, free-living bacteriovore. The MCG lab has obtained the complete genome sequence of C. owczarzaki (Suga et al. 2013) and it is currently trying to obtain the genome sequence of M. vibrans. RNAseq data is available from both taxa. Comparative analyses has shown that Filasterea are key to unravel the genetic repertoire of the unicellular ancestor of animals and to provide insights into the origin of Metazoa.  Interestingly, metabarcoding analyses of ribosomal 18S in marine environments have failed to recover other filasterean representatives (Del Campo & Ruiz-Trillo, 2013; Del Campo et al., 2015), suggesting this clade may not be especially abundant in natural ecosystems.

References:

-Shalchian-Tabrizi, K., Minge, M. A., Espelund, M., Orr, R., Ruden, T., Jakobsen, K. S., & Cavalier-Smith, T. (2008). Multigene phylogeny of choanozoa and the origin of animals. PLoS ONE, 3(5), e2098.
-Torruella, G., Derelle, R., Paps, J., Lang, B. F., Roger, A. J., Shalchian-Tabrizi, K., & Ruiz-Trillo, I. (2012). Phylogenetic relationships within the Opisthokonta based on phylogenomic analyses of conserved single-copy protein domains. Mol Biol Evol, 29(2), 531–544.

-Torruella, G., de Mendoza, A., Grau-Bové, X., Antó, M., Chaplin, M. A., del Campo, J., et al. (2015). Phylogenomics Reveals Convergent Evolution of Lifestyles in Close Relatives of Animals and Fungi. Current Biology : CB, 25(18), 2404–2410.

-Suga, H., Chen, Z., de Mendoza, A., Sebe-Pedros, A., Brown, M. W., Kramer, E., et al. (2013). The Capsaspora genome reveals a complex unicellular prehistory of animals. Nat Commun, 4, 2325. http://doi.org/10.1038/ncomms3325

-del Campo, J., & Ruiz-Trillo, I. (2013). Environmental survey meta-analysis reveals hidden diversity among unicellular opisthokonts. Mol Biol Evol, 30(4), 802–805. http://doi.org/10.1093/molbev/mst006

-del Campo, J., Mallo, D., Massana, R., de Vargas, C., Richards, T. A., & Ruiz-Trillo, I. (2015). Diversity and distribution of unicellular opisthokonts along the European coast analysed using high-throughput sequencing. Environ Microbiol, 17(9), 3195–3207. http://doi.org/10.1111/1462-2920.12759