Limnology of Organic Lake, Antarctica, a meromictic lake that contains high concentrations of dimethyl sulfide

Franzmann, P.D.; Deprez, Patrick P.; Burton, H. R.; Hoff, John van den

doi:10.1071/mf9870409

Cited by 37 publications

(27 citation statements)

References 18 publications

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“…Antarctica's Organic Lake is a shallow, hypersaline lake and contains the highest concentration of dimethylsulfide reported in natural water environments (35). The water temperatures are below Ϫ10°C, and the salinity exceeds 160 psu (practical salinity units) (36).…”

Section: Resultsmentioning

confidence: 99%

Novel N4 Bacteriophages Prevail in the Cold Biosphere

Zhan

Buchan

Chen

2015

Appl Environ Microbiol

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bColiphage N4 is a lytic bacteriophage discovered nearly half a century ago, and it was considered to be a "genetic orphan" until very recently, when several additional N4-like phages were discovered to infect nonenteric bacterial hosts. Interest in this genus of phages is stimulated by their unique genetic features and propagation strategies. To better understand the ecology of N4-like phages, we investigated the diversity and geographic patterns of N4-like phages by examining 56 Chesapeake Bay viral communities, using a PCR-clone library approach targeting a diagnostic N4-like DNA polymerase gene. Many new lineages of N4-like phages were found in the bay, and their genotypes shift from the lower to the upper bay. Interestingly, signature sequences of N4-like phages were recovered only from winter month samples, when water temperatures were below 4°C. An analysis of existing metagenomic libraries from various aquatic environments supports the hypothesis that N4-like phages are most prolific in colder waters. In particular, a high number of N4-like phages were detected in Organic Lake, Antarctica, a cold and hypersaline system. The prevalence of N4-like phages in the cold biosphere suggests these viruses possess yet-to-be-determined mechanisms that facilitate lytic infections under cold conditions. A s the most abundant microbial form, viruses play important roles in shaping host population structures, mediating genetic exchange between hosts, and modulating trophic transfer in marine food webs (1-3). Marine viral metagenomic studies suggest that viruses encompass the largest genetic repertoire in the ocean (4, 5), yet the functions of ϳ70% of the putative genes identified in viral metagenomic studies remain unknown (6). Recently, several novel phages infecting dominant marine bacteria have been isolated from the ocean (7,8). Both cultivation techniques and molecular approaches suggest that a great many marine viruses await discovery.Bacteriophage N4 was first isolated from sewer waters using Escherichia coli as a host nearly half a century ago (9) and remained a "genetic orphan" for decades, as no other genetically similar phages were characterized. Phage N4 has several unique features with regard to its morphology, physiology, and genome that have made it a focus of study. It has a 70-nm isocahedral capsid, and its genome size is 70 kb. More remarkably, N4 is the only known phage that does not rely on host RNA polymerase for early transcription (10, 11). Instead, it contains a DNA-dependent virionencapsidated RNA polymerase (vRNAP), which is coinjected with viral DNA into its host and initiates transcription (12). The phage also exhibits a lysis-inhibited infection cycle and an extremely large burst size (ca. 3,000 phages per cell), suggestive of a novel mechanism of cell lysis regulation (13,14).The recent renewed interest in the ecology of N4 was prompted by the isolation from a coastal estuary of two new N4-like phages, which infect bacteria of the marine Roseobacter lineage (15). Roseobacters are a widely ...

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Section: Resultsmentioning

confidence: 99%

Novel N4 Bacteriophages Prevail in the Cold Biosphere

Zhan

Buchan

Chen

2015

Appl Environ Microbiol

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“…It is shallow (6.8 m) and has variable surface water temperatures ( À 14 to þ 15 1C) while remaining sub-zero throughout most of its depth (Franzmann et al, 1987b;Gibson et al, 1991;Gibson, 1999). The lake has a high organic load generated from autochthonous production, and input from penguins and terrestrial algae (for example, in soaks, shallow ephemeral streams and depressions), and nutrient turnover is expected to be slow due to the constraints imposed on microbial activity by the lake's hypersalinity (B230 g l À 1 maximum salinity) and low temperature (Franzmann et al, 1987b;Gibson et al, 1991;Gibson, 1999). The salt and marine biota in the lake originate from seawater that was trapped in a basin B3000 years BP when the continental ice sheet receded and the land rose above sea level (Bird et al, 1991;Zwartz et al, 1998;Gibson, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…The salt and marine biota in the lake originate from seawater that was trapped in a basin B3000 years BP when the continental ice sheet receded and the land rose above sea level (Bird et al, 1991;Zwartz et al, 1998;Gibson, 1999). The bottom water of Organic Lake is unusual due to the absence of hydrogen sulfide and the high concentration of the gas dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and polysulfides (Deprez et al, 1986;Franzmann et al, 1987b;Gibson et al, 1991;. Concentrations of DMS as high as 5000 nM have been recorded in Organic Lake (Gibson et al, 1991), 100 times the maximum concentration recorded from seawater in the adjacent Prydz Bay and at least 1000 times that of the open Southern Ocean (Curran and Jones, 1998).…”

Section: Introductionmentioning

confidence: 99%

Metagenomic insights into strategies of carbon conservation and unusual sulfur biogeochemistry in a hypersaline Antarctic lake

et al. 2013

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Organic Lake is a shallow, marine-derived hypersaline lake in the Vestfold Hills, Antarctica that has the highest reported concentration of dimethylsulfide (DMS) in a natural body of water. To determine the composition and functional potential of the microbial community and learn about the unusual sulfur chemistry in Organic Lake, shotgun metagenomics was performed on size-fractionated samples collected along a depth profile. Eucaryal phytoflagellates were the main photosynthetic organisms. Bacteria were dominated by the globally distributed heterotrophic taxa Marinobacter, Roseovarius and Psychroflexus. The dominance of heterotrophic degradation, coupled with low fixation potential, indicates possible net carbon loss. However, abundant marker genes for aerobic anoxygenic phototrophy, sulfur oxidation, rhodopsins and CO oxidation were also linked to the dominant heterotrophic bacteria, and indicate the use of photo-and lithoheterotrophy as mechanisms for conserving organic carbon. Similarly, a high genetic potential for the recycling of nitrogen compounds likely functions to retain fixed nitrogen in the lake. Dimethylsulfoniopropionate (DMSP) lyase genes were abundant, indicating that DMSP is a significant carbon and energy source. Unlike marine environments, DMSP demethylases were less abundant, indicating that DMSP cleavage is the likely source of high DMS concentration. DMSP cleavage, carbon mixotrophy (photoheterotrophy and lithoheterotrophy) and nitrogen remineralization by dominant Organic Lake bacteria are potentially important adaptations to nutrient constraints. In particular, carbon mixotrophy relieves the extent of carbon oxidation for energy production, allowing more carbon to be used for biosynthetic processes. The study sheds light on how the microbial community has adapted to this unique Antarctic lake environment.

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“…Organic Lake is a shallow (7 m) hypersaline (≈230 g L −1 maximum salinity) meromictic lake with a high concentration of dimethylsulphide (≈120 μg L −1 ) in its anoxic monimolimnion (17,18). Water temperature at the surface of the lake can vary from −14 to +15°C while remaining subzero at depth (19,20). The lake is eutrophic, with organic material sourced both from autochthonous production and input from penguins and terrestrial algae.…”

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confidence: 99%

Virophage control of antarctic algal host–virus dynamics

Yau¹,

Lauro²,

DeMaere³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

252

324

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Viruses are abundant ubiquitous members of microbial communities and in the marine environment affect population structure and nutrient cycling by infecting and lysing primary producers. Antarctic lakes are microbially dominated ecosystems supporting truncated food webs in which viruses exert a major influence on the microbial loop. Here we report the discovery of a virophage (relative of the recently described Sputnik virophage) that preys on phycodnaviruses that infect prasinophytes (phototrophic algae). By performing metaproteogenomic analysis on samples from Organic Lake, a hypersaline meromictic lake in Antarctica, complete virophage and near-complete phycodnavirus genomes were obtained. By introducing the virophage as an additional predator of a predator-prey dynamic model we determined that the virophage stimulates secondary production through the microbial loop by reducing overall mortality of the host and increasing the frequency of blooms during polar summer light periods. Virophages remained abundant in the lake 2 y later and were represented by populations with a high level of major capsid protein sequence variation (25-100% identity). Virophage signatures were also found in neighboring Ace Lake (in abundance) and in two tropical lakes (hypersaline and fresh), an estuary, and an ocean upwelling site. These findings indicate that virophages regulate host-virus interactions, influence overall carbon flux in Organic Lake, and play previously unrecognized roles in diverse aquatic ecosystems.metagenomics | metaproteomics | East Antarctica | Vestfold Hills | microbial ecology

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Limnology of Organic Lake, Antarctica, a meromictic lake that contains high concentrations of dimethyl sulfide

Cited by 37 publications

References 18 publications

Novel N4 Bacteriophages Prevail in the Cold Biosphere

Novel N4 Bacteriophages Prevail in the Cold Biosphere

Metagenomic insights into strategies of carbon conservation and unusual sulfur biogeochemistry in a hypersaline Antarctic lake

Virophage control of antarctic algal host–virus dynamics

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