Richelia

Richelia
	Bright-field microscopy image of epiphytic cyanobacterial symbiont Richelia rhizosoleniae SC01 9 (indicated by arrows) attached to a host diatom Chaetoceros sp. (c). Scale bar, 50 μm.
Scientific classification
Domain:	Bacteria
Kingdom:	Bacillati
Phylum:	Cyanobacteriota
Class:	Cyanophyceae
Order:	Nostocales
Family:	Nostocaceae
Genus:	Richelia; J.Schmidt, 1901
Species
	Richelia intracellularis C.H.Ostenfeld ex J.Schmidt, 1901; Richelia sinica Shen and Li 1989 (recommended for removal); Non-LPSN Richelia rhizosoleniae (Lemmermann 1899) Foster et al., 2022; "Ca. Richelia exalis Delmont et al., 2021; Richelia euintracellularis Foster et al., 2022;

Richelia is a genus of nitrogen-fixing, filamentous, heterocystous and cyanobacteria. They exist as both free-living organisms as well as symbionts within potentially up to 13 diatoms distributed throughout the global ocean. As a symbiont, Richelia can associate epiphytically and as endosymbionts within the periplasmic space between the cell membrane and cell wall of diatoms.

Richelia has been divided into several species on a genomic basis. Despite not being recognized by the LPSN, they remain useful in talking about the differences in genomic content and lifestyle of the groups they refer to.