Glaucocystophytes are freshwater algae that possess an almost-intact cyanobacterium, referred to as a cyanelle, as their photosynthetic organelle. Because the cyanelle represents an intermediate state in plastid evolution, glaucocystophytes have been the subject of several studies to characterize the genetics and biochemistry of their cyanelles. However, only a small handful of older studies exist on the composition of their lipids, particularly two major plastid lipids, mono-and digalactosyldiacylglycerol (MGDG and DGDG, respectively), found in all photosynthetic life. Our study has used a modern mass spectrometry approach, namely positive-ion electrospray ionization/mass spectrometry/mass spectrometry, to provide a fresh interpretation of the MGDG and DGDG composition of the species, Cyanophora paradoxa Korshikov and Glaucocystis nostochinearum Itzigsohn, representing two glaucocystophyte genera. We have found that the major forms of MGDG and DGDG (with sn-1/sn-2 regiochemistry) are 20:5/16:0 MGDG, 20:5/20:5 MGDG, 20:5/16:0 DGDG, and 20:5/20:5 DGDG. A comparison of these four forms, along with other more minor forms of MGDG and DGDG, to two examples of cyanobacteria has revealed that glaucocystophytes do not share intact forms of MGDG and DGDG with extant cyanobacteria, but may have maintained certain C16 and C18 cyanobacterial fatty acids.

Glaucocystophytes are a group of evolutionarily important freshwater algae that have an almost intact cyanobacterium, referred to as a cyanelle, as the photosynthetic organelle. Because of this, they have been the subject of a large number of studies over the past few decades on how a cyanobacterium transitioned into a chloroplast. However, studies on their lipid composition have lagged behind those on other areas of glaucocystophyte cell biology. To this end, we have examined the sterol composition of Cyanophora paradoxa Korshikov and Glaucocystis nostochinearum Itzigsohn in order to identify sterols left unidentified in previous studies. We have found that two isolates of G. nostochinearum and one of C. paradoxa uniformly produced three sterols: 24-methylcholest-5-en3b-ol, 24-ethylcholesta-5,22E-dien-3b-ol, and 24-ethylcholest-5-en-3b-ol.

Karenia brevis is a harmful marine dinoflagellate that forms yearly blooms in the Gulf of Mexico. Under normal growth conditions, K. brevis forms two predominant sterols (24R)-4a-methyl-5a-ergosta-8(14),22-dien-3b-ol (gymnodinosterol) and its 27-nor isomer (brevesterol). At the current time, there are no published studies concerning the biosynthesis of these two sterols. We have therefore undertaken experiments in which K. brevis was exposed to the fungicide fenpropidine, an inhibitor of the D 14 -reductase and the D 8→7 -isomerase that operate in sterol biosynthesis in both fungal and plant systems. Such exposure to fenpropidine has produced two, tri-unsaturated intermediates. The identifications of these two K. brevis sterol biosynthesis intermediates, via gas chromatography/mass spectrometry and nuclear magnetic resonance spectroscopy techniques, were 4a-methyl-5a-ergosta-8,14,22-trien-3b-ol and 5a-ergosta-8,14,22-trien-3b-ol.