Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake

Journal Article · Fri Apr 15 00:00:00 EDT 2016 · Applied and Environmental Microbiology

DOI: https://doi.org/10.1128/AEM.00478-16 · OSTI ID:1319189

Li, Wei ^[1]; Podar, Mircea ^[2]; Morgan-Kiss, Rachael M. ^[1]

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1. Miami Univ., Oxford, OH (United States). Dept. of Microbiology
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division

The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (FlavobacteriaandMethylobacteriaceae) were independently associated with two key MCM lake microalgae (IsochrysisandChlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite ofChlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake. Single-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Ultimately, our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE; NSF; ORNL LDRD Director's R&D
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1319189
• Journal Information: Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 12 Vol. 82; ISSN 0099-2240
• Publisher: American Society for MicrobiologyCopyright Statement
• Country of Publication: United States
• Language: English