Sulfur-cycling chemolithoautotrophic microbial community dominates a cold, anoxic, hypersaline Arctic spring.

BACKGROUND: Gypsum Hill Spring, located in Nunavut in the Canadian High Arctic, is a rare example of a cold saline spring arising through thick permafrost. It perennially discharges cold (~ 7 °C), hypersaline (7-8% salinity), anoxic (~ 0.04 ppm O2), and highly reducing (~ - 430 mV) brines rich in sulfate (2.2 g.L-1) and sulfide (9.5 ppm), making Gypsum Hill an analog to putative sulfate-rich briny habitats on extraterrestrial bodies such as Mars. RESULTS: Genome-resolved metagenomics and metatranscriptomics were utilized to describe an active microbial community containing novel metagenome-assembled genomes and dominated by sulfur-cycling Desulfobacterota and Gammaproteobacteria. Sulfate reduction was dominated by hydrogen-oxidizing chemolithoautotrophic Desulfovibrionaceae sp. and was identified in phyla not typically associated with sulfate reduction in novel lineages of Spirochaetota and Bacteroidota. Highly abundant and active sulfur-reducing Desulfuromusa sp. highly transcribed non-coding RNAs associated with transcriptional regulation, showing potential evidence of putative metabolic flexibility in response to substrate availability. Despite low oxygen availability, sulfide oxidation was primarily attributed to aerobic chemolithoautotrophic Halothiobacillaceae. Low abundance and transcription of photoautotrophs indicated sulfur-based chemolithoautotrophy drives primary productivity even during periods of constant illumination. CONCLUSIONS: We identified a rare surficial chemolithoautotrophic, sulfur-cycling microbial community active in a unique anoxic, cold, hypersaline Arctic spring. We detected Mars-relevant metabolisms including hydrogenotrophic sulfate reduction, sulfur reduction, and sulfide oxidation, which indicate the potential for microbial life in analogous S-rich brines on past and present Mars. Video Abstract.

Identifying the recharge and salinization mechanisms of the Shekastian saline spring in southern Iran.

To identify the recharge, and the salinization mechanisms of Shekastian saline spring, appearing via thin limestone layers on the Shekastian stream bed, southern Iran, a comprehensive study was conducted using multi-tracing approach. Hydrochemical tracing indicated that the halite dissolution is the main salinity source for Shekastian spring. Similar to surface waters, spring salinity is amplified by evaporation during dry season, indicating that recharge comes from surface waters. The temperature of the spring water varies hourly, which is another sign that surface waters recharge the spring. Applying the discharge tracing method at two low-discharge times in two consecutive years by precise longitudinal discharge monitoring of the Shekastian stream above and below the spring site revealed that the main source of recharge for the Shekastian saline spring is water escape via thin limestone layers, located on a stream bed above the spring site. Results of isotope tracing indicated that Shekastian saline spring is recharged from evaporated surface water, subjecting to CO2 gas along subsurface flow path of recharging water. Geologic/geomorphologic evidences, supported by results of hydrochemical tracing, revealed that halite dissolution of Gachsaran evaporite formation by spring recharging water is the main salinization source for the Shekastian saline spring. To avoid salinization of Shekastian stream by Shekastian saline spring, draining the spring recharging water at downstream vicinity of spring recharging stream by building an underground interceptor drainage system is suggested, in which resulted in flow stopping the spring.

Draft genome sequence of Dethiosulfovibrio salsuginis DSM 21565T an anaerobic, slightly halophilic bacterium isolated from a Colombian saline spring.

A bacterium belonging to the phylum Synergistetes, genus Dethiosulfovibrio was isolated in 2007 from a saline spring in Colombia. Dethiosulfovibrio salsuginis USBA 82T (DSM 21565T= KCTC 5659T) is a mesophilic, strictly anaerobic, slightly halophilic, Gram negative bacterium with a diderm cell envelope. The strain ferments peptides, amino acids and a few organic acids. Here we present the description of the complete genome sequencing and annotation of the type species Dethiosulfovibrio salsuginis USBA 82T. The genome consisted of 2.68 Mbp with a 53.7% G + C. A total of 2609 genes were predicted and of those, 2543 were protein coding genes and 66 were RNA genes. We detected in USBA 82T genome six Synergistetes conserved signature indels (CSIs), specific for Jonquetella, Pyramidobacter and Dethiosulfovibrio. The genome of D. salsuginis contained, as expected, genes related to amino acid transport, amino acid metabolism and thiosulfate reduction. These genes represent the major gene groups of Synergistetes, related with their phenotypic traits, and interestingly, 11.8% of the genes in the genome belonged to the amino acid fermentation COG category. In addition, we identified in the genome some ammonification genes such as nitrate reductase genes. The presence of proline operon genes could be related to de novo synthesis of proline to protect the cell in response to high osmolarity. Our bioinformatics workflow included antiSMASH and BAGEL3 which allowed us to identify bacteriocins genes in the genome.

Draft genome and description of Consotaella salsifontis gen. nov. sp. nov., a halophilic, free-living, nitrogen-fixing alphaproteobacterium isolated from an ancient terrestrial saline spring.

A free-living, nitrogen-fixing, mesophilic and facultative aerobe, designated strain USBA 369T, was isolated from a terrestrial saline spring of the Colombian Andes. The non-sporulating rods (1.5×0.8 µm) with rounded ends stained Gram-negative and were motile by means of lophotrichous flagella. The strain grew optimally at 30 °C, at pH 6.9-7.5 and with 1.5 % (w/v) NaCl. The major fatty acids detected were C18 : 1ω7c and C19 : 0 cyclo ω8c, and the respiratory lipoquinone ubiquinone 10 (Q-10) was present. The genome consisted of 4.65 Mb with a DNA G+C content of 64.3 mol%. A total of 4371 genes were predicted and, of those, 4300 were protein coding genes and 71 were RNA genes. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain USBA 369T formed a different lineage within the class Alphaproteobacteria, order Rhizobiales, and DNA homology studies with the most closely related genera, Aurantimonas, Aureimonas and Rhizobium (95 % 16S rRNA gene sequence similarity), showed values of <15 %. The phylogenomic analysis provided evidence for clear phylogenetic divergence between strain USBA 369T and the closely related genera. On the basis of the phenotypic, chemotaxonomic and phylogenomic evidence, strain USBA 369T is considered to represent a novel genus and a novel species for which the name Consotaella salsifontis gen. nov., sp. nov. is proposed. The type strain is USBA 369T (=KCTC 22549T=CMPUJ U369T).