Identity and physiology of a new psychrophilic eukaryotic green alga, Chlorella sp., strain BI, isolated from a transitory pond near Bratina Island, Antarctica

• Published in: Extremophiles : life under extreme conditions 2008-09, Vol.12 (5), p.701-711
• Main Authors: Morgan-Kiss, Rachael M, Ivanov, Alexander G, Modla, Shannon, Czymmek, Kirk, Hüner, Norman P. A, Priscu, John C, Lisle, John T, Hanson, Thomas E
• Format: Article
• Language: English
• Subjects: Algae; Animal, plant and microbial ecology; Antarctic Regions; Aquatic plants; Biochemistry; Biological and medical sciences; Biomedical and Life Sciences; Biotechnology; Chlorella - classification; Chlorella - growth & development; Chlorella - physiology; Chlorella - ultrastructure; Chlorophyta - classification; Chlorophyta - isolation & purification; Chlorophyta - physiology; Cold Climate; Ecosystem; Electron Transport; Environmental changes; Eukaryotes; Fatty Acids - analysis; Food webs; Fundamental and applied biological sciences. Psychology; Geography; Ice shelves; Life Sciences; Low temperature; Marine biology; Microbial Ecology; Microbiology; Microorganisms; Original Paper; Photochemistry; Photosynthesis; Phylogeny; Pigments, Biological - isolation & purification; Polyunsaturated fatty acids; Ponds; Primary production; Various environments (extraatmospheric space, air, water)
• ISSN: 1431-0651; 1433-4909
• DOI: 10.1007/s00792-008-0176-4

Permanently low temperature environments are one of the most abundant microbial habitats on earth. As in most ecosystems, photosynthetic organisms drive primary production in low temperature food webs. Many of these phototrophic microorganisms are psychrophilic; however, functioning of the photosynthetic processes of these enigmatic psychrophiles (the “photopsychrophiles”) in cold environments is not well understood. Here we describe a new chlorophyte isolated from a low temperature pond, on the Ross Ice Shelf near Bratina Island, Antarctica. Phylogenetic and morphological analyses place this strain in the Chlorella clade, and we have named this new chlorophyte Chlorella BI. Chlorella BI is a psychrophilic species, exhibiting optimum temperature for growth at around 10°C. However, psychrophily in the Antarctic Chlorella was not linked to high levels of membrane-associated poly-unsaturated fatty acids. Unlike the model Antarctic lake alga, Chlamydomonas raudensis UWO241, Chlorella BI has retained the ability for dynamic short term adjustment of light energy distribution between photosystem II (PS II) and photosystem I (PS I). In addition, Chlorella BI can grow under a variety of trophic modes, including heterotrophic growth in the dark. Thus, this newly isolated photopsychrophile has retained a higher versatility in response to environmental change than other well studied cold-adapted chlorophytes.