Green Algae

Viable green algae were widely distributed in Siberian permafrost and were detected in 76 out of 293 permafrost cores. A total of 106 strains of green algae were isolated, and half of them, small non-motile globular cells, were identified as Chlorella spp. (Vishnivetskaya et al. 2001, 2005). Along with Chlorella spp., the species Chlorella vulgaris and Chlorella sacchorophilla and the genera Mychonastes sp., Pseudococcomyxa sp., Chodatia sp. (Chodatia tetrallontoidea), Stichococcus sp., Chlorococcum sp., Scotiellopsis sp. were identified using morphological criteria (Komarenko and Vasil'eva 1978; Andreeva 1998). Only three strains of green algae, classified as Chlorella sp., Mychonastes sp., Chlorococcum sp., were found in borehole 1/99 located in Beacon Valley, Antarctica (Gilichinsky et al. 2007b). These green algae were isolated from a permafrost layer sandwiched between buried ice horizons at depths of 14.1-14.8 m.

The 18S rRNA gene sequences of the viable green algae from Siberian (six strains) and Antarctic (three strains) permafrost were analyzed (Fig. 6.2). Among unicellular green algae were representatives of the genera Nannochloris, Chlorella (both in the order Chlorellales), Stichococcus (order Microthamniales), and Paradoxia (uncertain position) within Trebouxiophyceae. We found that two isolates from Siberian permafrost and three isolates from Antarctic permafrost were closely related to each other and to Nannochloris sp. JL4-6 (99%) and Chlorella protothecoides (97.8%).

Thus, the algae isolated from subsurface permafrost sediments had previously characterized relatives from cold environments, mostly from Antarctica. Members of the Chlorellaceae family, which consists of unicellular coccoid algae with simple morphology and small size, are widespread in Antarctic cold freshwater environments and cryptoendolitic communities (Friedmann and Ocampo-Friedmann 1976; Friedmann 1982; Wynn-Williams 1990; Vincent et al. 1993b; Vishniac 1993).

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Nannochloris sp. JL4-6 (AY195983)

- str. 594-GA199, Siberian permafrost 6.3 m str. Ant-1, Antarctic permafrost 14.5 m str. 193-GA188, Siberian permafrost 5.2 m str. Ant-2 and str. Ant-3, Antarctic permafrost 14.8-14.9 m

— Chlorella protothecoides var. acidicola 124, acidic soil (AJ439399)

|_r Chlorela sp. RA1 (Y14950) 6^- Nannochloris bacilaris (AB080300)

t- Nannochloris sp.AS2-10 (AY195968) Chlorela ellipsoidea SAG 211-1a, picoplankton (X63520) Stichococcus bacilaris D10-1 (AB055865)

Stichococcus deasonii UTEX 1706 (DQ275460) str. 594-GA18, Siberian permafrost 4.65 m Stichococcus jenerenss D4 (DQ275461) - Chlorela angustoellipsoidea MES A74 (AB006047) str. 594-GA375, Siberian permafrost 11.8 m Chlorella sp. MBIC10747 (AB183635) Chlorela saccharophia MBIC10042 (AB183578) Chlorela saccharophia SAG 211-9a, picoplankton (X63505)

Chlorellales

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Microthamniales

Chlorellales

- Choricystis sp. AS 5-1 (AY195970)

-Choricystis sp. Pic8/18P-11w (AY197629)

-Chlorophyte BC98, endosymbiont (AJ302940)

-str. 191-GA31, Siberian permafrost 34.0 m

- str. 294-GA206, Siberian permafrost 24.2 m

-Paradoxia multiseta LB 2460 (AY422078)

Trebouxiophyceae incertae sedis

Fig. 6.2 Phylogenetic relationship of green algae isolated from Siberian and Antarctic permafrost. Tree was created as described in Fig. 6.1. Sequences were deposited in GenBank

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