Horizontal gene transfer in the evolution of red algae. Image from Kobras and Falush, eLife, 2019 and photos by Andreas Weber (left panel), Debashish Bhattacharya (two middle panels), and Shin-ya Miyagishima (right panel). [CC BY 4.0]

The Galdieria sulphuraria MS1 genome sequence and gene models were not determined by the Joint Genome Insitute, but were downloaded from the Red Algal Resources to Promote Integrative Research in Algal Genomics webpage on October 31, 2019. All published models are available as ExternalModels. In order to ensure this genome is comparable to those sequenced and annotated by the JGI, we applied standard filters to ExternalModels to produce the initial GeneCatalog. A total of 615 external models were excluded based on one of the following classifications: 1) association with repetitive elements, 2) pseudogenes with internal stop codons, 3) alternative isoforms or overlapping transcript models, 4) alleles on secondary scaffolds, and 5) short models lacking functional annotation. Please note that this copy of the genome is not maintained by Rossoni et al. and is therefore not automatically updated. In order to allow comparative analyses with other algal genomes sequenced by the JGI, a copy of this genome is incorporated into PhycoCosm. The JGI Annotation Pipeline was used to add functional annotation to the genes.

Galdieria sulphuraria MS1 was found as a contaminant in samples from Yosemite National Park. It belongs to the Galdieriales, a monophyletic clade of polyextremophilic unicellular red algae. The Galdieriales and Cyanidiales thrive in acidic and thermal habitats, such as volcanoes, geysers, acid rivers, and geothermal plants. It is estimated that 1% of their gene inventory is derived from horizontal gene transfer (HGT), and the majority of these HGT-derived genes are related to polyextremophily (Rossoni et al., 2019).