Glaucocystophyta

1. Introduction
   1. Small group (3 genera known)
   2. Not economically important, consequently little studied
   3. Primarily important because of their unusual plastid, which retains a peptidoglycan cell wall
   4. If primary plastids (and by implication red and green algae) are monophyletic, then the glaucocystophytes may be the outgroup, which would give them a very important phylogenetic position.
   5. The Glaucocystophyta have caused tremendous confusion. Because they retain an unusual collection of ancestral character states, and have plastids that obviously resemble cyanobacteria, they have been treated quite differently by different authors.
   6. Synonomy
      1. Also called Glaucophyta, which is easier to pronounce, but the type genus is Glaucocystis, hence Glaucocystophyta is probably more correct.
2. Structure & metabolism
   1. May be motile, nonmotile, or have motile and nonmotile stages
   2. Motile stages
      1. Dorsiventral
      2. Two unequal flagella, with typical eukaryotic 9+2 arrangement
      3. Flagella have two rows of delicate hairs, reminiscent of flagellar hairs in green algae
         1. Do not have mastigonemes, which are characteristic of heterokonts.
      4. Cruciate microtubular root system with a multilayered structure (MLS); reminiscent of green algae
   3. Flat vessicles subtended by microtubules lie under the plasma membrane
      1. In some taxa these contain plates or fibers
      2. Reminiscent of the cortical alveoli found in the Alveolata (ciliates, apicomplexa, and dinoflagellates)
   4. Reserve polysaccharide is starch, which is accumulated outside of the plastid
   5. Cellulosic cell wall in Glaucocystis (Cyanophora lacks a cell wall, and Gloeochaete's cell wall has been reported to be non-cellulosic)
   6. Plastids
      1. Thin peptidoglycan cell wall on plastid, located between the two plastid outer membranes
      2. Chlorophyll a (only)
      3. Secondary pigments include beta-carotene, zeaxanthin, and beta-cryptoxanthin
      4. Phycobilisomes, consequently thylakoids are not stacked.
3. Classification
   1. Three genera
   2. Taxa to know:
      1. Glaucocystis
         1. Nonmotile, but retains two rudimentary flagella, which do not penetrate the cell wall
         2. Contrary to the text, there are several species of Glaucocystis
         3. Glaucocystis occurs in soft or acidic waters
      2. Cyanophora
         1. The best studied of the glaucocystophytes
         2. Chloroplast genome has been completely sequenced: genbank accession # U30821
         3. Chloroplast genome is 135,599 bp, contains 191 genes, and has an inverted repeat
      3. Gloeochaete
         1. Both motile and nonmotile stages
   3. Taxa probably incorrectly allied with Glaucocystophyta
      1. Glaucosphaera is a red alga rather than a glaucocystophyte (Bhattacharya et al., 1995)
   1. Paulinella resembles a testate amoeba, but has glaucocystophyte plastids; perhaps a secondary plastid?
4. Ecology
   1. Little is known
   2. Freshwater, sometimes collected from soil samples
   3. Rare, and typically not abundant
      1. I.e., even if you find a pond where a glaucocystophyte occurs, you may have to look at quite a few samples before you find it.

Required Reading: VdH: Chapter 4

Supplementary Reading:

Bhattacharya, D., T. Helmchen, C. Bibeau, and M. Melkonian. 1995. Comparisons of nuclear-encoded small-subunit ribosomal RNAs reveal the evolutionary position of the Glaucocystophyta. Mol. Biol. Evol. 12:415-420.

Kies, L., and B.P. Kremer. 1990. Phylum Glaucocsytophyta. In Lynn Margulis, J.O. Corliss, M. Melkonian, and D.J. Chapman, eds., Handbook of Protoctista, Jones and Bartlett, Boston.

L.J. Rothschild. 1989. Protozoa, Protista, Protoctista: what's in a name? J. Hist. Biol. 22:277-305.

Löffelhardt, W., and H.J. Bohnert. 1994. Molecular biology of cyanelles. In D.A. Bryant (ed.), The Molecular Biology of Cyanobacteria, Kluwer, Amsterdam.

Lockhart, P.J., C.J. Howe, D.A. Bryant, T.J. Beanland, and A.W.D. Larkum. 1992. Substitutional bias confounds inference of cyanelle origins from sequence data. J. Mol. Evol. 34:153-162.