IDENTIFICATION OF A PSYCHROPHILIC GREEN ALGA FROM LAKE BONNEY ANTARCTICA:CHLAMYDOMONAS RAUDENSISETTL. (UWO 241)CHLOROPHYCEAE.

An unusual psychrophilic green alga was isolated from the deepest portion of the photic zone (<0.1% of incident PAR) at a depth of 17 m in the permanently ice-covered lake, Lake Bonney, Antarctica. Here we identify and report the first detailed morphological and molecular examination of this Antarctic green alga, which we refer to as strain UWO 241. To determine the taxonomic identity, UWO 241 was examined using LM and TEM and partial sequences of the small subunit (SSU), internal transcribed spacer (ITS) 1 and ITS2 regions (including the 5.8S) of the ribosomal operon. These data were compared with those of previously described taxa. We identified UWO 241 as a strain ofChlamydomonas raudensisEttl (SAG 49.72).Chlamydomonas raudensisis closely related toC. noctigamaKorshikov (UTEX 2289) as well as foraminifer symbionts such asC. hedleyiLee, Crockett, Hagen et Stone (ATCC 50216). In addition, its morphology, pigment complement, and phototactic response to temperature are reported.Chlamydomonas raudensis(UWO 241) contains relatively high levels of lutein and low chla/ bratios (1.6±0.15), and the phototactic response was temperature dependent. The Antarctic isolate (UWO 241) included the typical photosynthetic pigments found in all chla/ bcontaining green algae. It possesses a small eyespot and, interestingly, was positively phototactic only at higher nonpermissive growth temperatures. Comparison of SSU and ITS rDNA sequences confirms the identification of the strain UWO 241 asC.raudensisEttl and contradicts the previous designation asC. subcaudataWille. [ABSTRACT FROM AUTHOR]