The psychrophilic strain CCCryo 005-99 of Chloromonas remiasii (Chlamydomonadaceae, Chlorophyta). Single cells show the original morphology with a lateral stigma, central nucleus and the characteristic posterior elongation (top middle). Usually cells form 2-celled or 4-celled sporangia (bottom right and top left). Flagella are often shed in cultures. [Photo credit: Thomas Leya, Fraunhofer IZI-BB]

Strain CCCryo 005-99 of Chloromonas remiasii is a psychrophilic (obligate cryophile) snow alga. It was isolated by Hau U. Ling on 2-Sept-1999 from red snow, also containing Sanguina nivaloides, collected that day by Torsten Mueller on the island of Spitsbergen, Svalbard, Norway (79°38'04.5" N 11°02'12.7" E / 79.634582, 11.036847). The sample was collected from a flat snow field with an icy meltwater stream crossing the eastern side of the of a small valley southeast of Sørgattet, below Reuschfjellet (739 m), during the field campaign KOL 07/1999. Further details can be accessed via the CCCryo collection.

The strain has an optimum growth temperature around 13 °C; it will cease growing at 18 °C and higher. 25-54% of all its fatty acids are saturated, 19-28% are monounsaturated and 27-47% are polyunsaturated depending on culture conditions. It has an active xanthophyll cycle and also produces alpha-tocopherol. Its genome size is estimated at 545 Mbp. The strain produces resting stages. The motile swarmers will easily shed their two flagella under unfavorable (e.g., too warm) conditions forming 2-celled (or 4, rarely 8) sporangia. Typical for its morphology are the asymmetrical body shape with one side flattened and a cytoplasm free posterior elongation/tail. Originally this strain was described as Chloromonas nivalis by the isolator based on morphological characteristics. Its name has been revised using molecular sequence data (Matsuzaki et al. 2018) using CCCryo 005-99 as an authentic strain.

C. remiasii has been sequenced as part of a larger research project studying the genetic comparison of psychrophilic snow algae to mesophilic algae such as Chlamydomonas reinhardtii. Differential expression profiles of transcriptome samples will explore changes in adaptation mechanisms with regard to responses to high and low light, blue versus red light, the effects of increased osmotic pressure resulting from salt stress, mimicking low/freezing temperatures, and special characteristics of snow algae with regard to carbon dioxide uptake. With these transcriptomes and the genome assembly, this study also establishes genetic data sets of psychrophilic snow algae valuable for further research in this field.

Reference

Matsuzaki, R., Nozaki, H., and Kawachi, M. (2018) Taxonomic revision of Chloromonas nivalis (Volvocales, Chlorophyceae) strains, with the new description of two snow-inhabiting Chloromonas species. PLoS ONE 13(3): e0193603. doi: 10.1371/journal.pone.0193603