The Genome Sequence of an Algal Strain of Nannochloropsis QH25.

Species of Nannochloropsis are single-celled Stramenopiles commonly used in microalgae-based technologies for the manufacturing of bioproducts. Nannochloropsis oceanica QH25 was isolated from an algal cultivation pond located in Imperial, Texas (USA). We used PacBio continuous long read (CLR) sequencing to produce a highly contiguous 29.34 Mb genome.

High-Quality Genome Assembly of Nannochloris desiccata 2437 and Its Associated Bacterial Community.

High-quality genome sequences were generated for the nonaxenic marine microalga Nannochloris desiccata UTEX 2437 and eight of its associated environmental bacterial species. N. desiccata UTEX 2437 is diploid, and its 20.738-Mbp nuclear genome sequence is assembled in 29 contigs.

Phylogenetic analyses and reclassification of the oleaginous marine species Nannochloris sp. "desiccata" (Trebouxiophyceae, Chlorophyta), formerly Chlorella desiccata, supported by a high-quality genome assembly.

Microalgae are diverse, with many gaps remaining in phylogenetic and physiological understanding. Thus, studying new microalgae species increases our broader comprehension of biological diversity, and evaluation of new candidates as algal production platforms can lead to improved productivity under a variety of cultivation conditions. Chlorella is a genus of fast-growing species often isolated from freshwater habitats and cultivated as a source of nutritional supplements. However, the use of freshwater increases competition with other freshwater needs. We identified Chlorella desiccata to be worthy of further investigation as a potential algae production strain, due to its isolation from a marine environment and its promising growth and biochemical composition properties. Long-read genomic sequencing was conducted for C. desiccata UTEX 2526, resulting in a high-quality, near chromosome level, diploid genome with an assembly length of 21.55 Mbp in only 18 contigs. We also report complete circular mitochondrial and chloroplast genomes. Phylogenomic and phylogenetic analyses using nuclear, chloroplast, 18S rRNA, and actin sequences revealed that this species clades within strains currently identified as Nannochloris (Trebouxiophyceae, Chlorophyta), leading to its reclassification as Nannochloris sp. "desiccata" UTEX 2526. The mode of cell division for this species is autosporulation, differing from the type species N. bacillaris. As has occurred across multiple microalgae genera, there are repeated examples of Nannochloris species reclassification in the literature. This high-quality genome assembly and phylogenetic analysis of the potential algal production strain Nannochloris sp. "desiccata" UTEX 2526 provides an important reference and useful tool for further studying this region of the phylogenetic tree.