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- All Subjects: Microbiology
- All Subjects: Nitrous oxide
- Creators: Barrila, Jennifer
The global transport and deposition of anthropogenic nitrogen (N) to downwind ecosystems are significant and continue to increase. Indeed, atmospheric deposition can be a significant source of N to many watersheds, including those in remote, unpopulated areas. Bacterial denitrification in lake sediments may ameliorate the effects of N loading by converting nitrate (NO3-) to N2 gas. Denitrification also produces nitrous oxide (N2O), a potent greenhouse gas. The ecological effects of atmospheric N inputs in terrestrial ecosystems and the pelagic zone of lakes have been well documented; however, similar research in lake sediments is lacking. This project investigates the effects N of deposition on denitrification and N2O production in lakes. Atmospheric N inputs might alter the availability of NO3- and other key resources to denitrifiers. Such altered resources could influence denitrification, N2O production, and the abundance of denitrifying bacteria in sediments. The research contrasts these responses in lakes at the ends of gradients of N deposition in Colorado and Norway. Rates of denitrification and N2O production were elevated in the sediments of lakes subject to anthropogenic N inputs. There was no evidence, however, that N deposition has altered sediment resources or the abundance of denitrifiers. Further investigation into the dynamics of nitric oxide, N2O, and N2 during denitrification found no difference between deposition regions. Regardless of atmospheric N inputs, sediments from lakes in both Norway and Colorado possess considerable capacity to remove NO3- by denitrification. Catchment-specific properties may influence the denitrifying community more strongly than the rate of atmospheric N loading. In this regard, sediments appear to be insulated from the effects of N deposition compared to the water column. Lastly, surface water N2O concentrations were greater in high-deposition lakes compared to low-deposition lakes. To understand the potential magnitude of deposition-induced N2O production, the greenhouse gas inventory methodology of Intergovernmental Panel on Climate Change was applied to available datasets. Estimated emissions from lakes are 7-371 Gg N y-1, suggesting that lakes could be an important source of N2O.
One of the identified health risk areas for human spaceflight is infectious disease, particularly involving environmental microorganisms already found on the International Space Station (ISS). In particular, bacteria belonging to the Burkholderia cepacia complex (Bcc) which can cause human disease in those who are immunocompromised, have been identified in the ISS water supply. This present study characterized the effect of spaceflight analog culture conditions on Bcc to certain physiological stresses (acid and thermal as well as intracellular survival in U927 human macrophage cells). The NASA-designed Rotating Wall Vessel (RWV) bioreactor was used as the spaceflight analogue culture system in these studies to grow Bcc bacterial cells under Low Shear Modeled Microgravity (LSMMG) conditions. Results show that LSMMG culture increased the resistance of Bcc to both acid and thermal stressors, but did not alter phagocytic uptake in 2-D monolayers of human monocytes.
Collectively, this work represents the first characterization of in vivo virulence and in vitro pathogenesis properties of D23580, the latter using advanced human surrogate models that mimic key aspects of the parental tissue. Results from these studies highlight the importance of studying infectious diseases using an integrated approach that combines actions of biological and physical networks that mimic the host-pathogen microenvironment and regulate pathogen responses.
phosphate or magnesium to the culture medium abrogated the fluid shear-related differences observed for A130 in LB medium for the acid or oxidative stress responses, respectively. Collectively, these findings indicate that like other Salmonella strains assessed thus far by our team, A130 responds to differences in physiological fluid shear, and that ion concentrations can modulate those responses.