Global distribution of Trebouxiophyceae diversity explored by high‐throughput sequencing and phylogenetic approaches

Abstract

Summary Trebouxiophyceae are a ubiquitous class of Chlorophyta encountered in aquatic and terrestrial environments. Most taxa are photosynthetic, and many acts as photobionts in symbiotic relationships, while others are free‐living. Trebouxiophyceae have also been widely investigated for their use for biotechnological applications. In this work, we aimed at obtaining a comprehensive image of their diversity by compiling the information of 435 freshwater, soil and marine environmental DNA samples surveyed with Illumina sequencing technology in order to search for the most relevant environments for bioprospecting. Freshwater and soil were most diverse and shared more than half of all operational taxonomic units (OTUs), however, their communities were significantly distinct. Oceans hosted the highest genetic novelty, and did not share any OTUs with the other environments; also, marine samples host more diversity in warm waters. Symbiotic genera usually found in lichens such as Trebouxia, Myrmecia and Symbiochloris were also abundantly detected in the ocean, suggesting either free‐living lifestyles or unknown symbiotic relationships with marine planktonic organisms. Altogether, our study opens the way to new prospection for trebouxiophycean strains, especially in understudied environments like the ocean.

Choricystis and Lewiniosphaera gen. nov. (Trebouxiophyceae Chlorophyta), two different green algal endosymbionts in freshwater sponges

“…However, they were probably often overlooked in monitoring programs of investigation for water quality because of its cell size (<3 μm). In contrast, Metz et al ( 2019 ) mostly found C. limnetica in freshwater and soil samples collected around the world. Both other species were not reported in that study, which could be the result of the intron distribution described above.…”

Lichen algae: the photosynthetic partners in lichen symbioses

“…Coccomyxa Schmidle -This trebouxiophycean algal genus is notable for the diversity of habitats and ecological circumstances in which its species are known to occur. Environmental surveys have found Coccomyxa sequences to be among the most widely distributed OTUs, and notably well represented in cold highlatitude climates (Metz et al 2019). It is commonly reported freeliving on terrestrial substrata and in aquatic environments, including those highly polluted with heavy metals and radioactive materials (see Gustavs et al 2017).…”

Thorsmoerkia curvula gen. et spec. nov. (Trebouxiophyceae, Chlorophyta), a semi-terrestrial microalga from Iceland exhibits high levels of unsaturated fatty acids

“…In the last years, several new lineages of trebouxiophycean algae have been discovered including the description of new genera, suggesting that the diversity of this group is still underexplored (Neustupa et al 2013;Song et al 2015;Vančurová et al 2015;Ulrich and Röske 2018;Darienko and Pröschold 2019). This goes along with a recent metagenomic study showing that the most diverse trebouxiophycean communities are found in freshwater and soil environments (Metz et al 2019). Like in the present study, integrative taxonomic approaches combining morphological and molecular traits will improve the knowledge about biodiversity in the diverse class of Trebouxiophyceae (e.g., Muggia et al 2018).…”