Type 1 Chlorophyceae - Mychonastes homosphaera (Skuja) Kalina et Puncocharova

Several isolates of Type 1 have been found from three different sites.  This type is the most abundant coccoid chlorophyte among our winter isolates. The different isolates that have been examined by light microscopy are quite uniform, with a very thin plastid , no pyrenoids, and small granules in the cytoplasm.  Mature cells are spherical, but autospores are flattened on the adjoining sides.  Cells range from about 2-4 µm in diameter.

Type 1 can be distinguished from the other coccoid chlorophyte, Type 10, by the HaeIII fragments.

The 18S rDNA PCR-RFLP patterns of Type 1 produced with HaeIII, NciI, BstNI, TaqI, and MfeI are all identical to those predicted from the published 18S rDNA sequence for "Chlorella homosphaera" (GenBank accession X73996), an organism that has been renamed Mychonastes homosphaera by Kalina and Puncocharova.  The original description of C. homosphaera by Skuja fits our isolates except that his organisms were up to 11 µm in diameter and produced 4-8 autospores.  Our isolates rarely exceed 4 µm and typically produce 2 autospores.  Type 1 organisms are probably a variety of M. homosphaera.