Atlantis AT26-10

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Departure date
2013-12-29
Departure port
Puntarenas, Costa Rica
Arrival Date
2014-01-27
Arrival Port
Balboa, Panama
Spatial coverage
westlimit: -104.3071223;southlimit: 6.9727053;eastlimit : -79.4546163;northlimit: 16.7113855
Cruise Name
Chemosynthetic Microbial Communities at Deep-Sea Vents
Cruise ID
AT26-10
R2R Cruise
https://www.rvdata.us/search/cruise/AT26-10
Cruise DOI
https://doi.org/10.7284/900413
Vessel Name
Atlantis
Chief scientist
Sievert, Stefan
Keywords

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  • Thesis
    Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09) McNichol, Jesse C. ; Sievert, Stefan
    Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the deep-sea is food-starved, the autotrophic metabolism of hydrothermal vent Epsilonproteobacteria may be very important for deep-sea consumers. However, quantifying their metabolic activities in situ has remained difficult, and biochemical mechanisms underlying their autotrophic physiology are poorly described. To gain insight into environmental processes, an approach was developed for incubations of microbes at in situ pressure and temperature (25 MPa, 24°C) with various combinations of electron donors/acceptors (H2, O2 and NO3 and 13HCO3) as a tracer to track carbon fixation. During short (18-24 h) incubations of low-temperature vent fluids from Crab Spa (9°N East Pacific Rise), the concentration of electron donors/acceptors and cell numbers were monitored to quantify microbial processes. Measured rates were generally higher than previous studies, and the stoichiometry of microbially-catalyzed redox reactions revealed new insights into sulfur and nitrogen cycling. Single-cell, taxonomically-resolved tracer incorporation showed Epsilonproteobacteria dominated carbon fixation, and their growth efficiency was calculated based on electron acceptor consumption. Using these data, in situ primary productivity, microbial standing stock, and average biomass residence time of the deep-sea vent subseafloor biosphere were estimated. Finally, the population structures of the most abundant genera Sulfurimonas and Thioreductor were shown to be strongly influenced by pO2 and temperature respectively, providing a mechanism for niche differentiation in situ. To gain insights into the core biochemical reactions underlying autotrophy in Epsilonprotebacteria, a theoretical metabolic model of Sulfurimonas denitrificans was developed. Validated iteratively by comparing in silico yields with data from chemostat experiments, the model generated hypotheses explaining critical, yet so far unresolved reactions supporting chemoautotrophy in Epsilonproteobacteria. For example, it provides insight into how energy is conserved during sulfur oxidation coupled to denitrification, how reverse electron transport produces ferredoxin for carbon fixation, and why aerobic growth yields are only slightly higher compared to denitrification. As a whole, this thesis provides important contributions towards understanding core mechanisms of chemoautrophy, as well as the in situ productivity, physiology and ecology of autotrophic Epsilonproteobacteria.