Papers by Svetlana Fernandes
Systems Biogeochemistry of Major Marine Biomes
FEMS Microbiology Letters, 2021
Kinetics of thiosulfate oxidation, product and intermediate formation, and 34S fractionation, wer... more Kinetics of thiosulfate oxidation, product and intermediate formation, and 34S fractionation, were studied for the members of Alphaproteobacteria Paracoccus sp. SMMA5 and Mesorhizobium thiogangeticum SJTT, the Betaproteobacteria member Pusillimonas ginsengisoli SBO3, and the Acidithiobacillia member Thermithiobacillus sp. SMMA2, during chemolithoautotrophic growth in minimal salts media supplemented with 20 mM thiosulfate. The two Alphaproteobacteria oxidized thiosulfate directly to sulfate, progressively enriching the end-product with 34S; Δ34Sthiosulfate-sulfate values recorded at the end of the two processes (when no thiosulfate was oxidized any further) were −2.9‰ and −3.5‰, respectively. Pusillimonas ginsengisoli SBO3 and Thermithiobacillus sp. SMMA2, on the other hand, oxidized thiosulfate to sulfate via tetrathionate intermediate formation, with progressive 34S enrichment in the end-product sulfate throughout the incubation period; Δ34Sthiosulfate-sulfate, at the end of the t...
FEMS Microbiology Letters, 2020
ABSTRACTThe ecology of aerobic microorganisms is never explored in marine oxygen minimum zone (OM... more ABSTRACTThe ecology of aerobic microorganisms is never explored in marine oxygen minimum zone (OMZ) sediments. Here we reveal aerobic bacterial communities along ∼3 m sediment-horizons of the eastern Arabian Sea OMZ. Sulfide-containing sediment-cores retrieved from 530 mbsl (meters beneath the sea-level) and 580 mbsl were explored at 15–30 cm intervals, using metagenomics, pure-culture-isolation, genomics and metatranscriptomics. Genes for aerobic respiration, and oxidation of methane/ammonia/alcohols/thiosulfate/sulfite/organosulfur-compounds, were detected in the metagenomes from all 25 sediment-samples explored. Most probable numbers for aerobic chemolithoautotrophs and chemoorganoheterotrophs at individual sample-sites were up to 1.1 × 107 (g sediment)-1. The sediment-sample collected from 275 cmbsf (centimeters beneath the seafloor) of the 530-mbsl-core yielded many such obligately aerobic isolates belonging to Cereibacter, Guyparkeria, Halomonas, Methylophaga, Pseudomonas and ...
Biogeosciences, 2020
To explore the potential role of tetrathionate in the sedimentary sulfur cycle, population ecolog... more To explore the potential role of tetrathionate in the sedimentary sulfur cycle, population ecology of microorganisms capable of metabolizing this polythionate was revealed at 15-30 cm resolution along two, ∼ 3 m long, cores collected from 530 and 580 m below the sea level, off India's west coast, within the oxygen minimum zone (OMZ) of the Arabian Sea. Metagenome analysis along the cores revealed widespread occurrence of genes involved in the formation, oxidation, and reduction of tetrathionate; high diversity and relative abundance were also detected for bacteria that are known to render these metabolisms in vitro. Results of slurry culture of the sediment samples in thiosulfate-or tetrathionate-containing microbial growth media, data obtained via pure-culture isolation, and finally metatranscriptome analyses corroborated the in situ functionality of the tetrathionate-forming, tetrathionate-oxidizing, and tetrathionate-reducing microorganisms. Ion chromatography of pore waters revealed the presence of up to 11.1 µM thiosulfate in the two cores, whereas tetrathionate remained undetected in spectroscopic assay based on its reaction with cyanide. While thiosulfate oxidation by chemolithotrophic bacteria prevalent in situ is the apparent source of tetrathionate in this ecosystem, high biochemical and geochemical reactivity of this polythionate could be instrumental in its cryptic status in the sulfur cycle. Potential abiotic origin of tetrathionate in the sediment horizon explored could neither be ruled out nor confirmed from the geochemical information available. On the other hand, tetrathionate potentially present in the system can be either oxidized to sulfate or reduced back to thiosulfate/sulfide via chemolithotrophic oxidation and respiration by native bacterial populations, respectively. Up to 2.01 mM sulfide present in the sediment cores may also reduce tetrathionate abiotically to thiosulfate and elemental sulfur. However, in the absence of measured data for O 2 or other oxyanions having possibilities of serving as electron acceptors, the biogeochemical modalities of the oxidative half of the tetrathionate cycle remained unresolved.
Bhattacharya et al.: Sediment microbiomes across a continental margin tings and water column oxyg... more Bhattacharya et al.: Sediment microbiomes across a continental margin tings and water column oxygenation regimes across the continental margins. got a fellowship from the Department of Science and Technology, GoI. Nibendu Mondal got fellowships from the Science and Engineering Research Board, GoI (under the grant EMR/2016/002703) and Bose Institute. Sumit Chatterjee received a fellowship from the Department of Biotechnology, GoI. Financial support. This research has been supported by the Earth System Sciences Organization, Ministry of Earth Sciences (grant no. MoES/36/00IS/Extra/19/2013) and Bose Institute (Intramural Faculty Grants). The research cruise SSK42 was also funded by the Ministry of Earth Sciences, GoI, via GAP2303. Review statement. This paper was edited by Tina Treude and reviewed by two anonymous referees.
Journal of Earth System Science, 2020
Geomicrobiology of sulfur-boron-dominated, neutral-pH hydrothermal systems was revealed in a Tran... more Geomicrobiology of sulfur-boron-dominated, neutral-pH hydrothermal systems was revealed in a Trans-Himalayan spring named Lotus Pond, located at 4436 m, in Puga Valley, Ladakh (India), where water boils at 85°C. Water sampled along Lotus Pond's outCow (vent to an adjacent river called Rulang), representing an 85-14°C gradient, had high microbial diversity and boron/chloride/sodium/sulfate/ thiosulfate concentration; potassium/silicon/sulBde/sulBte was moderately abundant, whereas cesium/ lithium small but definite. Majority of the bacterial genera identiBed in the 85-72°C samples have no laboratory-growth reported at [45°C, and some of those mesophiles were culturable. Sulfur-species concentration and isotope-ratio along the hydrothermal gradient, together with the distribution of genera having sulfur-oxidizing members, indicated chemolithotrophic activities in the 85-72°C sites. While biodiversity increased in the vent-to-river trajectory all-day, maximum rise was invariably between the vent (85-81°C) and the 78-72°C site; below 72°C, diversity increased gradually. Biodiversity of the ventwater exhibited diurnal Cuxes relatable to the sub-surface-processes-driven temporal Cuxes in physicochemical properties of the discharge. Snow-melts inBltrating (via tectonic faults) the *160°C geothermal reservoir located within the breccia, at *450 m depth, apparently transport mesophilic microbes into the thermal waters. As these microorganisms emanate with the vent-water, some remain alive, illustrating that natural bacterial populations are more heat-resilient than their laboratory counterparts. Keywords. Sulfur-boron hot spring; hot spring geomicrobiology; geochemistry of hot spring waters; microbial community dynamics along hydrothermal gradients; mesophilic bacteria in high-temperature habitats; in-situ resilience to heat.
Marine and Petroleum Geology, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
<p&amp... more <p>Here we present high-resolution biogeochemical study using nitrogen/carbon isotope ratio measurement and molecular proxies from a sediment core (length = 2.9 m) collected from the center (588 mbsl; Lat: 16<sup>0</sup>49.88’N and Long: 71<sup>0</sup> 58.55’ E) of the oxygen minimum zone off west coast of India. The core archives the depositional record covering 1.114 to 12.025 ky BP. The concentrations of total organic carbon (TOC) and total nitrogen (TN) range from 0.7 to 4.9 wt% and 0.068 to 0.5 wt % respectively. TOC and TN show parallel trends and the TOC/TN ratio varies within a narrow range of 8 to 11.5. The δ<sup>13</sup>C values range from -20.5‰ to -21.9‰ (V-PDB). The TOC/TN and δ<sup>13</sup>C suggest typical marine organic matter source. This observation is also further supported by the n-alkane distribution pattern where the dominance of nC<sub>21</sub> to nC<sub>24</sub> and the absence of odd alkane dominance over even suggest predominantly marine organic source. The δ<sup>15</sup>N profile shows a steady increase from 5.7‰ at 203 cmbsf (5.5 ky BP) to 7.5‰ at 2 cmbsf (~1ky BP) suggesting gradual increase in denitrification possibly liked to reduced ventilation in the Arabian Sea, whereas, between 5.5 to 12 ky BP, the δ<sup>15</sup>N values show marked fluctuations (5.2 to 7.1‰) possibly indicating variable level of oxygenation which in turn controlled the extent of denitrification. Possible influence of diagenesis (microbial degradation of organic matter) on the δ<sup>15</sup>N values also need to be investigated for a better understanding of the water column processes.</p>
Scientific Reports, 2020
Little is known about life in the boron-rich hot springs of Trans-Himalayas. Here, we explore the... more Little is known about life in the boron-rich hot springs of Trans-Himalayas. Here, we explore the geomicrobiology of a 4438-m-high spring which emanates ~70 °C-water from a boratic microbialite called Shivlinga. Due to low atmospheric pressure, the vent-water is close to boiling point so can entropically destabilize biomacromolecular systems. Starting from the vent, Shivlinga’s geomicrobiology was revealed along the thermal gradients of an outflow-channel and a progressively-drying mineral matrix that has no running water; ecosystem constraints were then considered in relation to those of entropically comparable environments. The spring-water chemistry and sinter mineralogy were dominated by borates, sodium, thiosulfate, sulfate, sulfite, sulfide, bicarbonate, and other macromolecule-stabilizing (kosmotropic) substances. Microbial diversity was high along both of the hydrothermal gradients. Bacteria, Eukarya and Archaea constituted >98%, ~1% and <1% of Shivlinga’s microbiome, ...
Metabolically-active obligate aerobes are unheard-of in tightly-anoxic environments. Present cult... more Metabolically-active obligate aerobes are unheard-of in tightly-anoxic environments. Present culture-independent and culture-dependent investigations revealed aerobic microbial communities along two, ~3-meter-long sediment-cores underlying the eastern Arabian Sea oxygen minimum zone, where high H2S disallows O2influx from the water-column. While genes for aerobic respiration byaa3-/cbb3-type cytochrome-coxidases and cytochrome-bdubiquinol oxidase, and aerobic oxidation of methane/ammonia/alcohols/thiosulfate/sulfite/organosulfur-compounds, were present across the cores, so were live aerobic, sulfur-chemolithoautotrophs and chemoorganoheterotrophs. The 8820-years-old, highly–sulfidic, methane-containing sediment-sample from 275 cmbsf of 530 mbsl yielded many such obligately-aerobic bacterial-isolates that died upon anaerobic incubation with alternative electron-acceptors/fermentative-substrates. Several metatranscriptomic reads from this sediment-sample matched aerobic-respiration-/o...
To explore the potential role of tetrathionate in the sulfur cycle of marine sediments, the popul... more To explore the potential role of tetrathionate in the sulfur cycle of marine sediments, the population ecology of tetrathionate-forming, oxidizing, and respiring microorganisms was revealed at 15-30 cm resolution along two, ~3-m-long, cores collected from 530- and 580-mbsl water-depths of Arabian Sea, off India west coast, within the oxygen minimum zone (OMZ). Metagenome analysis along the two sediment-cores revealed widespread occurrence of the structural genes that govern these metabolisms; high diversity and relative-abundance was also detected for the bacteria known to render these processes. Slurry-incubation of the sediment-samples, pure-culture isolation, and metatranscriptome analysis, corroborated the in situ functionality of all the three metabolic-types. Geochemical analyses revealed thiosulfate (0-11.1 micro Molar), pyrite (0.05-1.09 wt %), iron (9232-17234 ppm) and manganese (71-172 ppm) along the two sediment-cores. Pyrites (via abiotic reaction with MnO2) and thiosulf...
While geographically-/geologically-distinct hot springs harbor different levels of microbial dive... more While geographically-/geologically-distinct hot springs harbor different levels of microbial diversity, some of them encompass several such taxa which have no strain reported for laboratory growth at >45° C. We, therefore, hypothesized that native geomicrobial factors could be potent determinants of the microbial habitability of hot spring environments. To test this hypothesis, aquatic microbial communities were revealed metataxonomically, and considered in the context of spring-water chemistry, along the 85-14° C hydrothermal gradient of a sulfur-boron spring named Lotus Pond located at 4,436 m, within the Puga geothermal area of the Indian Trans-Himalayan region of Ladakh. Water samples were studied from four distinct sites along Lotus Ponds spring-water transit from the vent to an adjacent river called Rulang. Insinuations obtained from geomicrobiological data were tested via pure-culture growth experiments in habitat-inspired media. Microbial diversities were found to be high...
Scientific reports, Jan 6, 2018
Biogeochemistry of oxygen minimum zone (OMZ) sediments, which are characterized by high input of ... more Biogeochemistry of oxygen minimum zone (OMZ) sediments, which are characterized by high input of labile organic matter, have crucial bearings on the benthic biota, gas and metal fluxes across the sediment-water interface, and carbon-sulfur cycling. Here we couple pore-fluid chemistry and comprehensive microbial diversity data to reveal the sedimentary carbon-sulfur cycle across a water-depth transect covering the entire thickness of eastern Arabian Sea OMZ, off the west coast of India. Geochemical data show remarkable increase in average total organic carbon content and aerial sulfate reduction rate (J) in the sediments of the OMZ center coupled with shallowing of sulfate methane transition zone and hydrogen sulfide and ammonium build-up. Total bacterial diversity, including those of complex organic matter degraders, fermentative and exoelectrogenic bacteria, and sulfate-reducers (that utilize only simple carbon compounds) were also found to be highest in the same region. The above ...
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Papers by Svetlana Fernandes