Denitrification and environmental factors influencing nitrate removal in Guaymas Basin hydrothermally altered sediments

Abstract

We measured potential nitrate removal and denitrification rates in hydrothermally altered sediments inhabited by Beggiatoa mats and adjacent brown oil stained sediments from the Guaymas Basin, Gulf of California. Sediments with Beggiatoa maintained slightly higher rates of potential denitrification than did brown sediments at 31.2 ± 12.1 versus 21.9 ± 1.4 µM N day−1, respectively. In contrast, the nitrate removal rates in brown sediments were higher than those observed in mat-hosting sediments at 418 ± 145 versus 174 ± 74 µM N day−1, respectively. Additional experiments were conducted to assess the responses of denitrifying communities to environmental factors [i.e., nitrate, sulfide, and dissolved organic carbon (DOC) concentration)]. The denitrifying community had a high affinity for nitrate (Km = 137 ± 91 µM NO3−), in comparison to other environmental communities of denitrifiers, and was capable of high maximum rates of denitrification (Vmax = 1164 ± 153 µM N day−1). The presence of sulfide resulted in significantly lower denitrification rates. Microorganisms with the potential to perform denitrification were assessed in these sediments using the bacterial 16S rRNA gene and nitrous oxide reductase (nosZ) functional gene libraries. The bacterial 16S rRNA gene clone library was dominated by Epsilonproteobacteria (38%), some of which (e.g., Sulfurimonas sp.) have a potential for sulfide-dependent denitrification. The nosZ clone library did not contain clones similar to pure culture denitrifiers; these clones were most closely associated with environmental clones.

Draft genome of an Aerophobetes bacterium reveals a facultative lifestyle in deep-sea anaerobic sediments

“…In this study, we found that the representative Aerophobetes bacterial strains were largely from deep-sea sediments, particularly areas of methane seepage and gas hydrate sediment. Methane cold seeps are rich in reductive solutions, and the adjacent subsurface sediments are anoxic [44,45]. Our result suggests that methane supply is not required for Aerophobetes bacteria in the subsurface sediment.…”

Impact of Seasonal Hypoxia on Activity and Community Structure of Chemolithoautotrophic Bacteria in a Coastal Sediment

“…Beggiatoaceae have previously been reported to cooccur with chemolithoautotrophic nitrate-reducing and sulfur-oxidizing Epsilonproteobacteria (Sulfurovum and Sulfurimonas) in the deep-sea Guyamas basin (50). Interestingly, station S2 in March showed the highest number of aclB gene copies of all stations and seasons (Fig.…”

Capturing Compositional Variation in Denitrifying Communities: a Multiple-Primer Approach That Includes Epsilonproteobacteria

“…This interest is evidenced by the numerous studies of denitrifier functional gene diversity that have been undertaken in a variety of aquatic environments, including estuarine sediments (3)(4)(5)(6)(7), freshwater systems (8)(9)(10)(11)(12), coastal marine waters and sediments (4,5,(13)(14)(15), oxygen minimum zones and anoxic basins (12,(16)(17)(18)(19)(20)(21)(22)(23), hydrothermal vents (24,25), and deep-sea sediments (26). The ability to denitrify exists across a wide breadth of bacteria and archaea (2) that may be favored under different environmental conditions.…”