Nitrate determines the bacterial habitat specialization and impacts microbial functions in a subsurface karst cave (original) (raw)
Related papers
Nitrogen, sulfur and carbon fluxes in the terrestrial subsurface are determined by the intersecting activi- ties of microbial community members, yet the organ- isms responsible are largely unknown. Metagenomic methods can identify organisms and functions, but genome recovery is often precluded by data com- plexity. To address this limitation, we developed subsampling assembly methods to re-construct high-quality draft genomes from complex samples. We applied these methods to evaluate the inter- linked roles of the most abundant organisms in biogeochemical cycling in the aquifer sediment. Community proteomics confirmed these activities. The eight most abundant organisms belong to novel lineages, and two represent phyla with no pre- viously sequenced genome. Four organisms are predicted to fix carbon via the Calvin–Benson– Bassham, Wood–Ljungdahl or 3-hydroxyproprionate/ 4-hydroxybutarate pathways. The profiled organisms are involved in the network of denitrification, dissimilatory nitrate reduction to ammonia, ammonia oxida- tion and sulfate reduction/oxidation, and require substrates supplied by other community members. An ammonium-oxidizing Thaumarchaeote is the most abundant community member, despite low ammonium concentrations in the groundwater. This organism likely benefits from two other relatively abundant organisms capable of producing ammo- nium from nitrate, which is abundant in the ground- water. Overall, dominant members of the microbial community are interconnected through exchange of geochemical resources.
Microbial Activity in Subterranean Ecosystems: Recent Advances
Applied Sciences, 2020
Of the several critical challenges present in environmental microbiology today, one is the assessment of the contribution of microorganisms in the carbon cycle in the Earth-climate system. Karstic subterranean ecosystems have been overlooked until recently. Covering up to 25% of the land surface and acting as a rapid CH4 sink and alternately as a CO2 source or sink, karstic subterranean ecosystems play a decisive role in the carbon cycle in terms of their contribution to the global balance of greenhouse gases. Recent data indicate that microbiota must play a significant ecological role in the biogeochemical processes that control the composition of the subterranean atmosphere, as well as in the availability of nutrients for the ecosystem. Nevertheless, there are still essential gaps in our knowledge concerning the budgets of greenhouse gases at the ecosystem scale and the possible feedback mechanisms between environmental-microclimatic conditions and the rates and type of activity o...
Environmental Chemistry, 2013
Environmental context Nitrate contamination of drinking water quality may be critical, particularly in rural areas where agricultural practices may release large amounts of nitrogen. Knowledge of the source of such contamination, mandatory for water supply management, can be successfully acquired by combining the natural stable isotopes of nitrate, boron isotopic ratios and microbiological indicators. A new approach based on measurements of nitrate and boron isotopic composition associated with microbiological indicators for the determination of nitrate origin in karstic groundwater (SW, France) is presented. Nitrate and boron isotopic data indicate an animal source of nitrate (δ15N–NO3–>5‰, δ18O–NO3–<10‰ and δ11B ~25‰). Microorganism detection (bacteriophages) confirmed contamination from animal sources and proved fast water transfer (2–3 days) from surface to groundwater.
Nitrates in karst systems: comparing impacted systems to a relatively unimpacted system
Karst aquifers are highly susceptible to contamination because of the connection with surface water. Nitrate contamination is common; with most karst aquifers exhibiting some degree of impact. This work assesses the potential impacts of anthropogenic activities on the Horn Hollow Valley (HHV) in Carter County Kentucky. HHV is a karst aquifer system that appears to be minimally impacted by nitrate and chloride contamination. Sampling of the HHV area was conducted from June 2005 to November 2006. Nitrate as nitrogen (NO3-N) concentrations were between 0.13 to 1.54 mg/L; chloride concentrations ranged from 1.43 to 66.3 mg/L. Impact from anthropogenic sources are observed at 1 mg/L for NO3-N and 13 mg/L for chloride. Sources of nitrate are primarily soil organic matter and mineralized fertilizers. In addition to mineralized fertilizers, chloride appears to be contributed from road salts. Compared to waters from three other systems: the Mammoth Cave area, the southwestern Illinois sinkhole plain, and the Missouri Ozarks-Salem Plateau; waters from HHV exhibited lower concentrations of both NO3-N and chloride. Waters from Mammoth Cave and the Missouri Ozarks tended to have higher NO3-N concentrations and similar chloride concentrations. Waters from southwestern Illinois had higher NO3-N concentrations and chloride concentrations. Overall, the karst aquifer of HHV appears to be a relatively pristine system, with minor human impacts.