Phylogenetic position of someChlorella species within the chlorococcales based upon complete small-subunit ribosomal RNA sequences

Abstract

Complete small-subunit rRNA (16S-like rRNA) coding region sequences were determined for eight species of the Chlorococcales (Chlorophyceae). The genera investigated includePrototheca, Ankistrodesmus, Scenedesmus, and fiveChlorella species. Distance matrix methods were used to infer a phylogenetic tree that describes evolutionary relationships between several plant and green algal groups. The tree exhibits a bifurcation within the Chlorococcales consistent with the division into Oocystaceae and Scenedesmaceae, but three of the fiveChlorella species are more similar to other algae than toChlorella vulgaris. All of the sequences contain primary and secondary structural features that are characteristic of 16S-like rRNAs of chlorophytes and higher plants.Anikstrodesmus stipitatus, however, contains a 394-bp group I intervening sequence in its 16S-like rRNA coding region.