Affiliation:
1. Center for Ecology and Evolutionary Biology, 5289 University of Oregon, Eugene, Oregon 97403-5289
2. Department of Chemistry and Biochemistry, California Polytechnic State University, San Luis Obispo, California 93407
3. Thermal Biology Institute and Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana 59717
Abstract
ABSTRACT
Members of the rhodophytan order Cyanidiales are unique among phototrophs in their ability to live in extreme environments that combine low pH levels (∼0.2 to 4.0) and moderately high temperatures of 40 to 56°C. These unicellular algae occur in far-flung volcanic areas throughout the earth. Three genera (
Cyanidium
,
Galdieria
, and
Cyanidioschyzon
) are recognized. The phylogenetic diversity of culture isolates of the Cyanidiales from habitats throughout Yellowstone National Park (YNP), three areas in Japan, and seven regions in New Zealand was examined by using the chloroplast RuBisCO large subunit gene (
rbcL
) and the 18S rRNA gene. Based on the nucleotide sequences of both genes, the YNP isolates fall into two groups, one with high identity to
Galdieria sulphuraria
(type II) and another that is by far the most common and extensively distributed Yellowstone type (type IA). The latter is a spherical, walled cell that reproduces by internal divisions, with a subsequent release of smaller daughter cells. This type, nevertheless, shows a 99 to 100% identity to
Cyanidioschyzon merolae
(type IB), which lacks a wall, divides by “fission”-like cytokinesis into two daughter cells, and has less than 5% of the cell volume of type IA. The evolutionary and taxonomic ramifications of this disparity are discussed. Although the 18S rRNA and
rbcL
genes did not reveal diversity among the numerous isolates of type IA, chloroplast short sequence repeats did show some variation by location within YNP. In contrast, Japanese and New Zealand strains showed considerable diversity when we examined only the sequences of 18S and
rbcL
genes. Most exhibited identities closer to
Galdieria maxima
than to other strains, but these identities were commonly as low as 91 to 93%. Some of these Japanese and New Zealand strains probably represent undescribed species that diverged after long-term geographic isolation.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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