From AT26-10\u00a0cruise report (01/29/2014):
\nDOB: An Integrated Study of Energy Metabolism, Carbon Fixation, and Colonization Mechanisms in Chemosynthetic Microbial Communities at Deep-Sea Vents
\nCruise Report by the CIW research team: Dr. Ileana Perez-Rodriguez, Mr. Matt Rawls and Dr. Dionysis I. Foustoukos
\nThe CIW team was responsible for the shipboard continuous culturing incubations of vent fluids collected from Crab Spa and Tica hot springs during the AT26-10 expedition at 9oN EPR by utilizing our high-pressure bioreactor (Fig. 1). This was accomplished through a collaborative effort with Jeff Seewald and Sean Sylva (WHOI), who deployed isobaric gas-tight samplers (IGTs) to collect hydrothermal vent fluids at the diffuse flow sites. Experiments were designed to study the cycling to N through the metabolic processes of denitrification and dissimilatory nitrate reduction to ammonia (DNRA) under in-situ deep-sea vent temperature and pressure conditions.
We studied the evolution of nitrate reducing microorganisms at mesophilic (30oC) and thermophilic (50oC) conditions at pressures ranging from 5 to 250 bar. Vent fluids (16 IGTs) were delivered in the bioreactor and homogeneously mixed with aqueous media solution enriched in dissolved nitrate, hydrogen and 13C labeled bicarbonate to facilitate the growth of nitrate reducing microorganisms (Fig. 2). The two distinct sets of experiments were lasted for 356 and 100 hours. In short, experimental results constrained the function and metabolic rates of the denitrifying microbial communities in the Crab Spa fluids, while DNRA metabolic pathways were identified for the populations residing in the moderate temperature vent fluids (60oC) of the Alvinella colony at Tica.
\nDuring the course of the experiments we monitored the growth of deep-sea microbial communities by measuring the concentrations of dissolved aqueous species directly involved in nitrate based metabolism, such as NO3, NH4, H2 and H2S. We also monitored cell densities by utilizing an epi-fluorescence microscope (Sievert, WHOI). Dissolved gas and NH4+ concentrations were attained by gas and ion chromatography (Seewald - Sylva, WHOI). Subsamples were also collected for a number of offshore analysis to determine: i) the 15N/14N isotope composition of NO3-,/NH4+ and constrain kinetic isotope effects associated with denitrification/DNRA (Perez-Rodriguez, CIW), ii) to study the rates of autotrophic carbon fixation by NanoSIMS (Musat, UFZ), iii) to perform single cell genomics on the microbial populations grown in the bioreactor (Ramunas, Bigelow) and (iv) to isolate and characterize novel microogranisms from the communities cultured in our experiments (Perez-Rodriguez, CIW and Vetriani, Rutgers).
This dataset includes results from shipboard high-pressure incubations of diffuse flow vent fluids collected from the Crab Spa (9.8398\u00ba N, 104.2913\u00ba W) and Alvinella (9.8398\u00ba N, 104.2915\u00ba W) sites at East Pacific Rise during the AT26-10 oceanographic expedition in January 2014. Reported parameters include dates and time elapsed, flow rate, temperature, pressure, and pH, and concentrations of NO3, NH4, H2, H2S, CH4.
\nVent fluids used in shipboard incubations were corrected from diffuse flow vent sites at the East Pacific Rise (2503 m): Crab Spa (9.8398\u00ba N, 104.2913\u00ba W) and Alvinella (9.8398\u00ba N, 104.2915\u00ba W) (see description in McNichol et al. [2016]). Fluids were collected using isobaric gas-tight samplers [Seewald et al., 2002] prior to their transfer to the shipboard continuous culture system [Foustoukos and Perez-Rodriguez, 2015]. Here, high-pressure incubations (250 bars) were conducted at mesophilic (30 \u00baC) and thermophilic (50 \u00baC) conditions to constrain the function and metabolic rates of denitrifying and DNRA microbial communities residing at Crab Spa and Alvinella, respectively. To enhance the activity of nitrate-respiring anaerobic bacteria, an NO3- (5 mm) and H2(aq) (1.30 mM)-enriched medium was introduced in the high-pressure incubations under strictly anaerobic conditions. Dissolved HCO3- (7.3 mm, 13C labeled) was used as added carbon source. Vent fluids were introduced at a flow rate of 0.042 mL/min, while growth medium was added at a rate of 0.0042 mL/min. The two sets of experiments were performed for 356 (Crab Spa) and 50 hours (Alvinella). Direct cell counts were conducted by staining cells with 0.1% acridine orange and counting them with a fluorescence microscope. 15N/14N isotopic analysis of the NO3-, NH4+ and biomass were conducted with a Thermo Scientific Delta VPlus mass spectrometer and CE Instruments NA 2500 series elemental analyzer (EA).
\nReferences:
\nFoustoukos, D., and I. Perez-Rodriguez (2015), A continuous culture system for assessing microbial activities in the piezosphere, Applied and Environmental Microbiology, 81(19), 6850-6856.
\nMcNichol, J., S. P. Sylva, F. Thomas, C. D. Taylor, S. M. Sievert, and J. S. Seewald (2016), Assessing microbial processes in deep-sea hydrothermal systems by incubation at in situ temperature and pressure, Deep Sea Research Part I: Oceanographic Research Papers, 115, 221-232.
\nSeewald, J. S., K. W. Doherty, T. R. Hammar, and S. P. Liberatore (2002), A new gas-tight isobaric sampler for hydrothermal fluids, Deep-Sea Research, Part I: Oceanographic Research Papers, 49(1), 189-196.
BCO-DMO Processing:
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