Scholarly Work - Microbiology & Cell Biology
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3494
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Item Acquisition of elemental sulfur by sulfur-oxidising Sulfolobales(Wiley, 2024-08) Fernandes-Martins, Maria C.; Springer, Carli; Colman, Daniel R.; Boyd, Eric S.Elemental sulfur (S80)-oxidising Sulfolobales (Archaea) dominate high-temperature acidic hot springs (>80°C, pH <4). However, genomic analyses of S80-oxidising members of the Sulfolobales reveal a patchy distribution of genes encoding sulfur oxygenase reductase (SOR), an S80 disproportionating enzyme attributed to S80 oxidation. Here, we report the S80-dependent growth of two Sulfolobales strains previously isolated from acidic hot springs in Yellowstone National Park, one of which associated with bulk S80 during growth and one that did not. The genomes of each strain encoded different sulfur metabolism enzymes, with only one encoding SOR. Dialysis membrane experiments showed that direct contact is not required for S80 oxidation in the SOR-encoding strain. This is attributed to the generation of hydrogen sulfide (H2S) from S80 disproportionation that can diffuse out of the cell to solubilise bulk S80 to form soluble polysulfides (Sx2−) and/or S80 nanoparticles that readily diffuse across dialysis membranes. The Sulfolobales strain lacking SOR required direct contact to oxidise S80, which could be overcome by the addition of H2S. High concentrations of S80 inhibited the growth of both strains. These results implicate alternative strategies to acquire and metabolise sulfur in Sulfolobales and have implications for their distribution and ecology in their hot spring habitats.Item Covariation of hot spring geochemistry with microbial genomic diversity, function, and evolution(Springer Science and Business Media LLC, 2024-08) Colman, Daniel R.; Keller, Lisa M.; Arteaga-Pozo, Emilia; Andrade-Barahona, Eva; St. Clair, Brian; Shoemaker, Anna; Cox, Alysia; Boyd, Eric S.The geosphere and the microbial biosphere have co-evolved for ~3.8 Ga, with many lines of evidence suggesting a hydrothermal habitat for life’s origin. However, the extent that contemporary thermophiles and their hydrothermal habitats reflect those that likely existed on early Earth remains unknown. To address this knowledge gap, 64 geochemical analytes were measured and 1022 metagenome-assembled-genomes (MAGs) were generated from 34 chemosynthetic high-temperature springs in Yellowstone National Park and analysed alongside 444 MAGs from 35 published metagenomes. We used these data to evaluate co-variation in MAG taxonomy, metabolism, and phylogeny as a function of hot spring geochemistry. We found that cohorts of MAGs and their functions are discretely distributed across pH gradients that reflect different geochemical provinces. Acidic or circumneutral/alkaline springs harbor MAGs that branched later and are enriched in sulfur- and arsenic-based O2-dependent metabolic pathways that are inconsistent with early Earth conditions. In contrast, moderately acidic springs sourced by volcanic gas harbor earlier-branching MAGs that are enriched in anaerobic, gas-dependent metabolisms (e.g. H2, CO2, CH4 metabolism) that have been hypothesized to support early microbial life. Our results provide insight into the influence of redox state in the eco-evolutionary feedbacks between thermophiles and their habitats and suggest moderately acidic springs as early Earth analogs.Item Sulfide oxidation by members of the Sulfolobales(Oxford University Press, 2024-05) Fernandes-Martins, Maria C.; Colman, Daniel R.; Boyd, Eric S.The oxidation of sulfur compounds drives the acidification of geothermal waters. At high temperatures (>80°C) and in acidic conditions (pH <6.0), oxidation of sulfide has historically been considered an abiotic process that generates elemental sulfur (S0) that, in turn, is oxidized by thermoacidophiles of the model archaeal order Sulfolobales to generate sulfuric acid (i.e. sulfate and protons). Here, we describe five new aerobic and autotrophic strains of Sulfolobales comprising two species that were isolated from acidic hot springs in Yellowstone National Park (YNP) and that can use sulfide as an electron donor. These strains significantly accelerated the rate and extent of sulfide oxidation to sulfate relative to abiotic controls, concomitant with production of cells. Yields of sulfide-grown cultures were ∼2-fold greater than those of S0-grown cultures, consistent with thermodynamic calculations indicating more available energy in the former condition than the latter. Homologs of sulfide:quinone oxidoreductase (Sqr) were identified in nearly all Sulfolobales genomes from YNP metagenomes as well as those from other reference Sulfolobales, suggesting a widespread ability to accelerate sulfide oxidation. These observations expand the role of Sulfolobales in the oxidative sulfur cycle, the geobiological feedbacks that drive the formation of acidic hot springs, and landscape evolution.Item Relationships between fluid mixing, biodiversity, and chemosynthetic primary productivity in Yellowstone hot springs(Wiley, 2023-01) Fernandes‐Martins, Maria C.; Colman, Daniel R.; Boyd, Eric S.The factors that influence biodiversity and productivity of hydrothermal ecosystems are not well understood. Here we investigate the relationship between fluid mixing, biodiversity, and chemosynthetic primary productivity in three co-localized hot springs (RSW, RSN, and RSE) in Yellowstone National Park that have different geochemistry. All three springs are sourced by reduced hydrothermal fluid, but RSE and RSN receive input of vapour phase gas and oxidized groundwaters, with input of both being substantially higher in RSN. Metagenomic sequencing revealed that communities in RSN were more biodiverse than those of RSE and RSW in all dimensions evaluated. Microcosm activity assays indicate that rates of dissolved inorganic carbon (DIC) uptake were also higher in RSN than in RSE and RSW. Together, these results suggest that increased mixing of reduced volcanic fluid with oxidized fluids generates additional niche space capable of supporting increasingly biodiverse communities that are more productive. These results provide insight into the factors that generate and maintain chemosynthetic biodiversity in hydrothermal systems and that influence the distribution, abundance, and diversity of microbial life in communities supported by chemosynthesis. These factors may also extend to other ecosystems not supported by photosynthesis, including the vast subterranean biosphere and biospheres beneath ice sheets and glaciers.Item Ecological dichotomies arise in microbial communities due to mixing of deep hydrothermal waters and atmospheric gas in a circumneutral hot spring.(American Society for Microbiology, 2021-09) Fernandes-Martins, Maria C.; Keller, Lisa M.; Munro-Ehrlich, Mason; Zimlich, Kathryn R.; Mettler, Madelyn K.; England, Alexis M.; Clare, Rita; Surya, Kevin; Shock, Everett L.; Colman, Daniel R.; Boyd, Eric S.Understanding the source and availability of energy capable of supporting life in hydrothermal environments is central to predicting the ecology of microbial life on early Earth when volcanic activity was more widespread. Little is known of the substrates supporting microbial life in circumneutral to alkaline springs, despite their relevance to early Earth habitats.Item Diversification of methanogens into hyperalkaline serpentinizing environments through adaptations to minimize oxidant limitation(Springer Science and Business Media LLC, 2020-11) Fones, Elizabeth M.; Colman, Daniel R.; Kraus, Emily A.; Stepanauskas, Ramunas; Templetin, Alexis S.; Spear, John R.; Boyd, Eric S.Metagenome assembled genomes (MAGs) and single amplified genomes (SAGs) affiliated with two distinct Methanobacterium lineages were recovered from subsurface fracture waters of the Samail Ophiolite, Sultanate of Oman. Lineage Type I was abundant in waters with circumneutral pH, whereas lineage Type II was abundant in hydrogen rich, hyperalkaline waters. Type I encoded proteins to couple hydrogen oxidation to CO2 reduction, typical of hydrogenotrophic methanogens. Surprisingly, Type II, which branched from the Type I lineage, lacked homologs of two key oxidative [NiFe]-hydrogenases. These functions were presumably replaced by formate dehydrogenases that oxidize formate to yield reductant and cytoplasmic CO2 via a pathway that was unique among characterized Methanobacteria, allowing cells to overcome CO2/oxidant limitation in high pH waters. This prediction was supported by microcosm-based radiotracer experiments that showed significant biological methane generation from formate, but not bicarbonate, in waters where the Type II lineage was detected in highest relative abundance. Phylogenetic analyses and variability in gene content suggested that recent and ongoing diversification of the Type II lineage was enabled by gene transfer, loss, and transposition. These data indicate that selection imposed by CO2/oxidant availability drove recent methanogen diversification into hyperalkaline waters that are heavily impacted by serpentinization.Item Roadmap for naming uncultivated Archaea and Bacteria(2020-08) Murray, Alison E.; Freudenstein, John; Gribaldo, Simonetta; Hatzenpichler, Roland; Hugenholtz, Philip; Kampfer, Peter; Konstantinidis, Konstantinos T.; Lane, Christopher E.; Papke, R. Thane; Parks, Donovan H.; Rossello-Mora, Ramon; Stott, Matthew B.; Sutcliffe, Iain C.; Thrash, J. Cameron; Venter, Stephanus N.; Whitman, William B.; Acinas, Silvia G.; Amann, Rudolf I.; Anantharaman, Karthik; Armengaud, Jean; Baker, Brett J.; Barco, Roman A.; Bode, Helge B.; Boyd, Eric S.; Brady, Carrie L.; Carini, Paul; Chain, Patrick S. G.; Colman, Daniel R.; DeAngelis, Kristen M.; Asuncion de los Rios, Maria; Estrada-de los Santos, Paulina; Dunlap, Christopher A.; Eisen, Jonathan A.; Emerson, David; Ettema, Thisjs J. G.; Eveillard, Damien R.; Girguis, Peter R.; Hentschel, Ute; Hollibaugh, James T.; Hug, Laura A.; Inskeep, William P.; Ivanova, Elena P.; Klenk, Hans-Peter; Li, Wen-Jun; Lloyd, Karen G.; Loffler, Frank E.; Makhalanyane, Thulani P.; Moser, Duane P.; Nunoura, Takuro; Palmer, Marike; Parro, Victor; Pedros-Alio, Carlos; Probst, Alexander J.; Smits, Theo H. M.; Steen, Andrew D.; Steenkamp, Emma T.; Spang, Anja; Stewart, Frank J.; Tiedje, James M.; Vandamme, Peter; Wagner, Michael; Wang, Feng-Ping; Yarza, Pablo; Hedlund, Brian P.; Reysenbach, Anna-LouiseThe assembly of single-amplified genomes (SAGs) and metagenome-assembled genomes (MAGs) has led to a surge in genome-based discoveries of members affiliated with Archaea and Bacteria, bringing with it a need to develop guidelines for nomenclature of uncultivated microorganisms. The International Code of Nomenclature of Prokaryotes (ICNP) only recognizes cultures as ‘type material’, thereby preventing the naming of uncultivated organisms. In this Consensus Statement, we propose two potential paths to solve this nomenclatural conundrum. One option is the adoption of previously proposed modifications to the ICNP to recognize DNA sequences as acceptable type material; the other option creates a nomenclatural code for uncultivated Archaea and Bacteria that could eventually be merged with the ICNP in the future. Regardless of the path taken, we believe that action is needed now within the scientific community to develop consistent rules for nomenclature of uncultivated taxa in order to provide clarity and stability, and to effectively communicate microbial diversity.Item Phylogenomic analysis of novel Diaforarchaea is consistent with sulfite but not sulfate reduction in volcanic environments on early Earth(2020-02) Colman, Daniel R.; Lindsay, Melody R.; Amenabar, Maximiliano J.; Fernandes-Martins, Maria C.; Roden, Eric R.; Boyd, Eric S.The origin(s) of dissimilatory sulfate and/or (bi)sulfite reducing organisms (SRO) remains enigmatic despite their importance in global carbon and sulfur cycling since at least 3.4 Ga. Here, we describe novel, deep-branching archaeal SRO populations distantly related to other Diaforarchaea from two moderately acidic thermal springs. Dissimilatory (bi)sulfite reductase homologs, DsrABC, encoded in metagenome assembled genomes (MAGs) from spring sediments comprise one of the earliest evolving Dsr lineages. DsrA homologs were expressed in situ under moderately acidic conditions. MAGs lacked genes encoding proteins that activate sulfate prior to (bi)sulfite reduction. This is consistent with sulfide production in enrichment cultures provided sulfite but not sulfate. We suggest input of volcanic sulfur dioxide to anoxic spring-water yields (bi)sulfite and moderately acidic conditions that favor its stability and bioavailability. The presence of similar volcanic springs at the time SRO are thought to have originated (>3.4 Ga) may have supplied (bi)sulfite that supported ancestral SRO. These observations coincide with the lack of inferred SO42− reduction capacity in nearly all organisms with early-branching DsrAB and which are near universally found in hydrothermal environments.Item Geobiological feedbacks, oxygen, and the evolution of nitrogenase(2019-02) Mus, Florence; Colman, Daniel R.; Peters, John W.; Boyd, Eric S.Biological nitrogen fixation via the activity of nitrogenase is one of the most important biological innovations, allowing for an increase in global productivity that eventually permitted the emergence of higher forms of life. The complex metalloenzyme termed nitrogenase contains complex iron-sulfur cofactors. Three versions of nitrogenase exist that differ mainly by the presence or absence of a heterometal at the active site metal cluster (either Mo or V). Mo-dependent nitrogenase is the most common while V-dependent or heterometal independent (Fe-only) versions are often termed alternative nitrogenases since they have apparent lower activities for N2 reduction and are expressed in the absence of Mo. Phylogenetic data indicates that biological nitrogen fixation emerged in an anaerobic, thermophilic ancestor of hydrogenotrophic methanogens and later diversified via lateral gene transfer into anaerobic bacteria, and eventually aerobic bacteria including Cyanobacteria. Isotopic evidence suggests that nitrogenase activity existed at 3.2 Ga, prior to the advent of oxygenic photosynthesis and rise of oxygen in the atmosphere, implying the presence of favorable environmental conditions for oxygen-sensitive nitrogenase to evolve. Following the proliferation of oxygenic phototrophs, diazotrophic organisms had to develop strategies to protect nitrogenase from oxygen inactivation and generate the right balance of low potential reducing equivalents and cellular energy for growth and nitrogen fixation activity. Here we review the fundamental advances in our understanding of biological nitrogen fixation in the context of the emergence, evolution, and taxonomic distribution of nitrogenase, with an emphasis placed on key events associated with its emergence and diversification from anoxic to oxic environments.Item Physiological adaptations to serpentinization in the Samail Ophiolite, Oman(2019-03) Fones, Elizabeth M.; Colman, Daniel R.; Kraus, Emily A.; Nothaft, Daniel B.; Poudel, Saroj; Rempfert, Kaitlin R.; Spear, John R.; Templeton, Alexis S.; Boyd, Eric S.Hydration of ultramafic rock during the geologic process of serpentinization can generate reduced substrates that microorganisms may use to fuel their carbon and energy metabolisms. However, serpentinizing environments also place multiple constraints on microbial life by generating highly reduced hyperalkaline waters that are limited in dissolved inorganic carbon. To better understand how microbial life persists under these conditions, we performed geochemical measurements on waters from a serpentinizing environment and subjected planktonic microbial cells to metagenomic and physiological analyses. Metabolic potential inferred from metagenomes correlated with fluid type, and genes involved in anaerobic metabolisms were enriched in hyperalkaline waters. The abundance of planktonic cells and their rates of utilization of select single-carbon compounds were lower in hyperalkaline waters than alkaline waters. However, the ratios of substrate assimilation to dissimilation were higher in hyperalkaline waters than alkaline waters, which may represent adaptation to minimize energetic and physiologic stress imposed by highly reducing, carbon-limited conditions. Consistent with this hypothesis, estimated genome sizes and average oxidation states of carbon in inferred proteomes were lower in hyperalkaline waters than in alkaline waters. These data suggest that microorganisms inhabiting serpentinized waters exhibit a unique suite of physiological adaptations that allow for their persistence under these polyextremophilic conditions.