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Molecular characterization of novel red green nonsulfur bacteria from five distinct hot spring communities in Yellowstone National Park.

ABSTRACT: We characterized and compared five geographically isolated hot springs with distinct red-layer communities in Yellowstone National Park. Individual red-layer communities were observed to thrive in temperatures ranging from 35 to 60 degrees C and at pH 7 to 9. All communities were dominated by red filamentous bacteria and contained bacteriochlorophyll a (Bchl a), suggesting that they represented novel green nonsulfur (GNS) bacteria. The in vivo absorption spectra of individual sites were different, with two sites showing unusual Bchl a protein absorption bands beyond 900 nm. We prepared and analyzed 16S rRNA libraries from all of these sites by using a combination of general bacterial primers and new GNS-specific primers described here. These studies confirmed the presence of novel GNS-like bacteria in all five communities. All GNS-like clones were most similar to Roseiflexus castenholzii, a red filamentous bacterium from Japan that also contains only Bchl a. Phylogenies constructed by using GNS-like clones from Yellowstone red-layer communities suggest the presence of a moderately diverse new "red" cluster within the GNS lineage. Within this cluster, at least two well-supported subclusters emerged: YRL-A was most similar to Roseiflexus and YRL-B appeared to be novel, containing no known isolates. While these patterns showed some site specificity, they did not correlate with observed Bchl a spectrum differences or obvious features of the habitat.

SUBMITTER: Boomer SM

PROVIDER: S-EPMC126577 | biostudies-literature | 2002 Jan

REPOSITORIES: biostudies-literature

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Molecular characterization of novel red green nonsulfur bacteria from five distinct hot spring communities in Yellowstone National Park.

Boomer Sarah M SM Lodge Daniel P DP Dutton Bryan E BE Pierson Beverly B

Applied and environmental microbiology 20020101 1

We characterized and compared five geographically isolated hot springs with distinct red-layer communities in Yellowstone National Park. Individual red-layer communities were observed to thrive in temperatures ranging from 35 to 60 degrees C and at pH 7 to 9. All communities were dominated by red filamentous bacteria and contained bacteriochlorophyll a (Bchl a), suggesting that they represented novel green nonsulfur (GNS) bacteria. The in vivo absorption spectra of individual sites were differen ...[more]

PMID: 11772644

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Project description:Chocolate Pots hot springs (CP) is a circumneutral-pH Fe-rich geothermal feature located in Yellowstone National Park. Previous Fe(III)-reducing enrichment culture studies with CP sediments identified close relatives of known dissimilatory Fe(III)-reducing bacterial (FeRB) taxa, including Geobacter and Melioribacter However, the abundances and activities of such organisms in the native microbial community are unknown. Here, we used stable isotope probing experiments combined with 16S rRNA gene amplicon and shotgun metagenomic sequencing to gain an understanding of the in situ Fe(III)-reducing microbial community at CP. Fe-Si oxide precipitates collected near the hot spring vent were incubated with unlabeled and 13C-labeled acetate to target active FeRB. We searched reconstructed genomes for homologs of genes involved in known extracellular electron transfer (EET) systems to identify the taxa involved in Fe redox transformations. Known FeRB taxa containing putative EET systems (Geobacter, Ignavibacteria) increased in abundance under acetate-amended conditions, whereas genomes related to Ignavibacterium and Thermodesulfovibrio that contained putative EET systems were recovered from incubations without electron donor. Our results suggest that FeRB play an active role in Fe redox cycling within Fe-Si oxide-rich deposits located at the hot spring vent.IMPORTANCE The identification of past near-surface hydrothermal environments on Mars emphasizes the importance of using modern Earth environments, such as CP, to gain insight into potential Fe-based microbial life on other rocky worlds, as well as ancient Fe-rich Earth ecosystems. By combining stable carbon isotope probing techniques and DNA sequencing technology, we gained insight into the pathways of microbial Fe redox cycling at CP. The results suggest that microbial Fe(III) oxide reduction is prominent in situ, with important implications for the generation of geochemical and stable Fe isotopic signatures of microbial Fe redox metabolism within Fe-rich circumneutral-pH thermal spring environments on Earth and Mars.

Project description:A culture-independent molecular phylogenetic survey was carried out for the bacterial community in Obsidian Pool (OP), a Yellowstone National Park hot spring previously shown to contain remarkable archaeal diversity (S. M. Barns, R. E. Fundyga, M. W. Jeffries, and N. R. Page, Proc. Natl. Acad. Sci. USA 91:1609-1613, 1994). Small-subunit rRNA genes (rDNA) were amplified directly from OP sediment DNA by PCR with universally conserved or Bacteria-specific rDNA primers and cloned. Unique rDNA types among > 300 clones were identified by restriction fragment length polymorphism, and 122 representative rDNA sequences were determined. These were found to represent 54 distinct bacterial sequence types or clusters (> or = 98% identity) of sequences. A majority (70%) of the sequence types were affiliated with 14 previously recognized bacterial divisions (main phyla; kingdoms); 30% were unaffiliated with recognized bacterial divisions. The unaffiliated sequence types (represented by 38 sequences) nominally comprise 12 novel, division level lineages termed candidate divisions. Several OP sequences were nearly identical to those of cultivated chemolithotrophic thermophiles, including the hydrogen-oxidizing Calderobacterium and the sulfate reducers Thermodesulfovibrio and Thermodesulfobacterium, or belonged to monophyletic assemblages recognized for a particular type of metabolism, such as the hydrogen-oxidizing Aquificales and the sulfate-reducing delta-Proteobacteria. The occurrence of such organisms is consistent with the chemical composition of OP (high in reduced iron and sulfur) and suggests a lithotrophic base for primary productivity in this hot spring, through hydrogen oxidation and sulfate reduction. Unexpectedly, no archaeal sequences were encountered in OP clone libraries made with universal primers. Hybridization analysis of amplified OP DNA with domain-specific probes confirmed that the analyzed community rDNA from OP sediment was predominantly bacterial. These results expand substantially our knowledge of the extent of bacterial diversity and call into question the commonly held notion that Archaea dominate hydrothermal environments. Finally, the currently known extent of division level bacterial phylogenetic diversity is collated and summarized.

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Molecular characterization of novel red green nonsulfur bacteria from five distinct hot spring communities in Yellowstone National Park.

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Molecular characterization of novel red green nonsulfur bacteria from five distinct hot spring communities in Yellowstone National Park.

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