Type 6 Trebouxiophyceae

Type 6 is spherical when at maximum size of about 6 µm, but is elliptical when smaller.  The chloroplast is also quite variable.  Small cells have a dark, dense plastid that is positioned at one end or along the side of the elliptical cell.  Larger cells have a thin parietal plastid.  A pyrenoid is visible in some cells.  A few cells, particularly in older cultures, have a structure that looks like a lipid droplet in the cytosol. Four autospores are typically produced. Cells range from about 2-6 µm in the long axis.

Type 6 Green coccoid can be distinguished from other trebouxiophytes by the HaeIII fragments. The gel on the left shows the HaeIII fragments and NciI fragments Type 6. We have found three isolates of Type 6, all isolated from plankton samples taken February, 1995 and February, 1996. Type 6 restriction fragments do not match those predicted from any published sequence.