''Guillardia'' is a genus of flagellate

cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anteri ...

algae belonging to the family Geminigeraceae, containing a secondary plastid within a reduced cytoplasmic compartment that contains a vestigial

nucleomorph Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. They are thought to be vestiges of primitive red and green algal nuclei that were engulfed by a larger eukaryote. Becaus ...

. There is only one characterised member of this genus, ''Guillardia theta''.

Genomes

''Guillardia theta'' was the first cryptophyte to have its nuclear genome sequenced. The genome contains 87 Mbp, encoding around 24,840 genes. The complete nucleomorph and plastid genomes have been sequenced, containing 551 kbp and 121 kbp respectively.

Optogenetic tools

Two anion-conducting

channelrhodopsins Channelrhodopsins are a subfamily of retinylidene proteins (rhodopsins) that function as light-gated ion channels. They serve as sensory photoreceptors in unicellular green algae, controlling phototaxis: movement in response to light. Expressed ...

were isolated from ''Guillardia theta'' that hyperpolarize neuronal membrane potential and are potent inhibitors of neural activity.

References

Cryptomonad genera {{Cryptomonad-stub