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The third and hottest water sample, Stevenson Island 72, comes from a deep trench east of Stevenson Island in the central portion of the lake, where small, well-developed hydrothermal vents coalesce along northwest-trending deep fissures that reach maximally 133 m depth, the deepest point in the lake (Morgan et al., 2003b). The fourth sample, West Thumb Canyon 129, represents hot vent water from a sublacustrine explosion crater in the western part of West Thumb basin, in the westernmost part of the lake (Morgan et al., 2003b). Reduced sulfur compounds (hydrogen sulfide, thiosulfate, sulfite) were quantified by a scaled-up modification of the microbore high-performance liquid chromatographic (HPLC) method of Vairavamurthy and Mopper (1990), using dithio-bis-nitropyridine (DTNP) derivatization.
Direct observations by SCUBA and ROV have revealed a wide range of hydrothermal features, including large hydrothermal chimneys; gas fumaroles; seepage of hot, shimmering water; and sulfur-oxidizing microbial mats growing around hot water seeps and vents (Remsen et al., 2002).
Examination of an ancient vent chimney revealed internal conduit structures with metal sulfide precipitates, indicating long-term hydrothermal activity (Cuhel et al., 2004).
In contrast, cool vent water with low chemosynthetic activity yielded predominantly phylotypes related to freshwater Actinobacterial clusters with a cosmopolitan distribution.
In-depth geophysical and geochemical exploration and lake floor mapping of Yellowstone Lake, the largest Alpine Lake in the United States, has revealed numerous sublacustrine hot vents and hydrothermal features in geothermally active areas on the lake bottom (Klump et al., 1988, 1995; Remsen et al., 1990; Morgan et al., 2003a, b).
Members of the Aquificales, most closely affiliated with the genus Sulfurihydrogenibium, are the most frequently recovered bacterial 16S r RNA gene phylotypes in the hottest samples; the detection of these thermophilic sulfur-oxidizing autotrophs coincided with maximal dark CO at temperatures of 50–60°C.
Vents at lower temperatures yielded mostly phylotypes related to the mesophilic gammaproteobacterial sulfur oxidizer Thiovirga. Analytical equipment was transported to Yellowstone National Park and set up as a field laboratory at the National Park Service Lake Station. Freshly collected samples for stable analytes were filtered through 0.2-μm filters (Supor-200, Pall Corp.) and aliquoted for the different analyses. Hydrothermal vent waters were collected in July 2003 from five locations (Table 1) in Yellowstone Lake for microbial community analysis by 16S r RNA gene sequencing (Table 1). The first two samples come from the Mary Bay area near the northeastern shore of the lake, one of the hydrothermally most active areas of Yellowstone Lake, with high heat flux and numerous hydrothermal vents (Morgan et al., 2003b): Mary Bay West 12 is a surface water sample taken above a nearshore bubbling warm fumarole in shallow water (1 m), and Mary Bay Canyon 28 represents warm deep water (52 m) below the sill of an underwater canyon in Mary Bay. Near-complete 16S r RNA genes were PCR-amplified with bacterial primers 8F (5); these primers were successful in recovering extremely diverse bacterial communities, including members of novel phyla (Teske et al., 2002). Phylogenetic ecology of the freshwater Actinobacteria ac I lineage. PCR products were cloned using the TOPO XL PCR cloning kit (Invitrogen Corporation, Carlsbad, CA, USA) following the manufacturers instructions, and sequenced at the sequencing center of the University of North Carolina with primers M13F (5). Here, we present results of a preliminary 16S r RNA gene clone library survey of the bacterial communities in five different thermal vent locations in Yellowstone Lake with distinct chemical signatures and distinct temperature-dependent chemosynthetic rates. The 16S r RNA gene clone libraries indicate the existence of distinct chemosynthetic bacterial communities, dominated either by Gammaproteobacteria affiliated with the mesophilic sulfur-oxidizing genus Thiovirga, or by phylotypes most closely related to cultured species and strains of the extremely thermophilic Aquificales. Hydrothermal springs and gas fumaroles in Yellowstone Lake, Yellowstone National Park, Wyoming. In contrast to the well-studied photosynthetic and chemosynthetic aerial hot spring communities of Yellowstone Park terrestrial habitats (Ward et al., 1998; Spear et al., 2005), systematic analyses of these Yellowstone Lake hydrothermal microbial communities are in their early stages, but have already demonstrated the potential for autotrophic, thermophilic chemosynthetic microbial communities. For example, the vents at Steamboat Point and Mary Bay at the northern edge of the lake, and deep-water vents off Stevenson island in the center of the lake, harbor chemosynthetic bacteria that assimilate dissolved inorganic carbon (DIC) in the dark at rates typically 0.08–0.5 μM C h (Cuhel et al., 2002).