Microbial community structure and sulfur biogeochemistry in mildly‐acidic sulfidic geothermal springs in Yellowstone National Park

Abstract

Geothermal and hydrothermal waters often contain high concentrations of dissolved sulfide, which reacts with oxygen (abiotically or biotically) to yield elemental sulfur and other sulfur species that may support microbial metabolism. The primary goal of this study was to elucidate predominant biogeochemical processes important in sulfur biogeochemistry by identifying predominant sulfur species and describing microbial community structure within high-temperature, hypoxic, sulfur sediments ranging in pH from 4.2 to 6.1. Detailed analysis of aqueous species and solid phases present in hypoxic sulfur sediments revealed unique habitats containing high concentrations of dissolved sulfide, thiosulfate, and arsenite, as well as rhombohedral and spherical elemental sulfur and/or sulfide phases such as orpiment, stibnite, and pyrite, as well as alunite and quartz. Results from 16S rRNA gene sequencing show that these sediments are dominated by Crenarchaeota of the orders Desulfurococcales and Thermoproteales. Numerous cultivated representatives of these lineages, as well as the Thermoproteales strain (WP30) isolated in this study, require complex sources of carbon and respire elemental sulfur. We describe a new archaeal isolate (strain WP30) belonging to the order Thermoproteales (phylum Crenarchaeota, 98% identity to Pyrobaculum/Thermoproteus spp. 16S rRNA genes), which was obtained from sulfur sediments using in situ geochemical composition to design cultivation medium. This isolate produces sulfide during growth, which further promotes the formation of sulfide phases including orpiment, stibnite, or pyrite, depending on solution conditions. Geochemical, molecular, and physiological data were integrated to suggest primary factors controlling microbial community structure and function in high-temperature sulfur sediments.

Predominant Acidilobus-Like Populations from Geothermal Environments in Yellowstone National Park Exhibit Similar Metabolic Potential in Different Hypoxic Microbial Communities

“…1) were sampled from August to November 2007 at the following locations: Norris Geyser Basin One Hundred Spring Plain (OSP), Monarch Geyser (MG), Cistern Spring (CIS), and Joseph's Coat Hot Springs-Scorodite Spring (JCHS). All sites have been characterized extensively for several years, and the geochemistry is reasonably stable in these systems (2,4,6,7,21,36). Subsequent samples from identical locations and with identical temperature values were obtained in 2009 and 2010 for reverse transcriptase assays as well as continued geochemical monitoring.…”

“…Organisms within the Desulfurococcales are abundant community members in high-temperature habitats of YNP, especially Acidilobus-like populations found in mildly acidic hypoxic environments containing elemental sulfur (4,20,21). Similar organisms are found in numerous other high-temperature sulfide-rich systems distributed globally (22)(23)(24)(25)(26)(27)(28).…”

Hydrogen Peroxide Cycling in High-Temperature Acidic Geothermal Springs and Potential Implications for Oxidative Stress Response

“…were measured using a modified version of the Winkler method (Macur et al, 2013). Briefly, a 60-mL syringe filled with geothermal spring water was capped immediately with a septum (zero headspace) to avoid ingassing of atmospheric O 2 , then treated with appropriate reagents and titrated against Na 2 S 2 O 3 .…”

“…Ferric iron concentrations were then calculated as the difference between total soluble iron and ferrous iron. Total dissolved sulfide (TS) was assessed using the amine sulfuric acid method (APHA, 1998;Macur et al, 2013;Jay et al, 2014) with 7.5 mL of unfiltered samples [to avoid rapid degassing of H 2 S(aq) upon filtration].…”

Viral assemblage composition in Yellowstone acidic hot springs assessed by network analysis

“…High temperatures (480C), low pH (pHo3) conditions generally favor Archaea-dominated communities (Bolduc et al, 2012). Bacteria and eukaryotes are few or in many cases, absent (Reysenbach et al, 1994;Blank et al, 2002;Kozubal et al, 2012;Macur et al, 2012;Jay et al, 2013). These extreme environmental conditions favor not only the Archaea but also result in a relatively simplified microbial community structure.…”