Phylogeny and lipid profiles of snow-algae isolated from Norwegian red-snow microbiomes

International audienceSnow algae blooms often form green or red coloured patches in melting alpine and polar snowfields w orldwide , y et little is known about their biolo gy, bio geo graphy, and species di v ersity. We inv estigated eight isolates collected fr om r ed snow in northern Norw ay, using a combination of morphology, 18S rRNA gene and internal transcribed spacer 2 (ITS2) genetic markers. Phylogenetic and ITS2 rRNA secondar y structur e anal yses assigned six isolates to the species Raphidonema nivale , Deuterostichococcus epilithicus , Chlor omonas r eticulata , and Xanthonema bristolianum. Two novel isolates belonging to the family Stichococcaceae (ARK-S05-19) and the genus Chloromonas (ARK-S08-19) were identified as potentially new species. In la borator y culti v ation, differ ences in the growth rate and fatty acid profiles wer e observ ed betw een the str ains. Chlorophyta w ere c har acterized by a bundant C18:3 n-3 fatty-acids with incr eases in C18:1 n-9 in the stationary phase, whilst Xanthonema (Ochrophyta) was c har acterized by a large proportion of C20:5 n-3, with increases in C16:1 n-7 in the stationary phase. In a further experiment, lipid droplet formation was studied in C. reticulata at the single-cell level using imaging flo w c ytometry. Our stud y esta b lishes new cultur es of snow algae, r ev eals nov el data on their biodi v ersity and bio geo graphy, and provides an initial c har acterization of physiological traits that shape natural communities and their ecophysiological properties