Project description:The diversity and environmental distribution of the nosZ gene, which encodes the enzyme responsible for the consumption of nitrous oxide, was investigated in marine and terrestrial environments using a functional gene microarray. The microbial communities represented by the nosZ gene probes showed strong biogeographical separation, with communities from surface ocean waters and agricultural soils significantly different from each other and from those in oceanic oxygen minimum zones. Atypical nosZ genes, usually associated with incomplete denitrification pathways, were detected in all the environments, including surface ocean waters. The abundance of nosZ genes, as estimated by quantitative PCR, was highest in the agricultural soils and lowest in surface ocean waters.
Project description:Oxygen deficient zones (ODZs) are major sites of net natural oceanic nitrous oxide (N2O) production and emissions. In order to understand changes in the magnitude of N2O production in response to global change, knowledge on the individual contributions of the major microbial pathways (nitrification and denitrification) to N2O production and their regulation is needed. In the ODZ of the coastal area off Peru, the sensitivity of N2O production to oxygen and organic matter was investigated using 15N-tracer experiments in combination with qPCR and microarray analysis of total and active functional genes targeting archaeal amoA and nirS as marker genes for nitrification and denitrification, respectively. Denitrification was responsible for the highest N2O production with mean 8.7 nmol L-1 d-1 but up to 118 ± 27.8 nmol L-1 d-1 just below the oxic-anoxic interface. Highest N2O production from AO of 0.16 ± 0.003 nmol L-1 d-1 occurred in the upper oxycline at O2 concentrations of 10 - 30 µmol L-1 which coincided with highest archaeal amoA transcripts/genes. Oxygen responses of N2O production varied with substrate, but production and yields were generally highest below 10 µmol L-1 O2. Particulate organic matter additions increased N2O production by denitrification up to 5-fold suggesting increased N2O production during times of high particulate organic matter export. High N2O yields from ammonium oxidation of 2.1% were measured, but the overall contribution to N2O production stays an order of magnitude behind denitrification as an N2O source. Hence, these findings show that denitrification is the most important N2O production process in low oxygen conditions fueled by organic carbon supply which implies a positive feedback of the total oceanic N2O sources in response to increasing oceanic deoxygenation. [SUBMITTER_CITATION]: Frey, C., Bange, H. W., Achterberg, E. P., Jayakumar, A., Löscher, C. R., Arévalo-Martínez, D. L., León-Palmero, E., Sun, M., Sun, X., Xie, R. C., Oleynik, S., and Ward, B. B.: Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru, Biogeosciences, 17, 2263-2287
Project description:Oxygen deficient zones (ODZs) are major sites of net natural oceanic nitrous oxide (N2O) production and emissions. In order to understand changes in the magnitude of N2O production in response to global change, knowledge on the individual contributions of the major microbial pathways (nitrification and denitrification) to N2O production and their regulation is needed. In the ODZ of the coastal area off Peru, the sensitivity of N2O production to oxygen and organic matter was investigated using 15N-tracer experiments in combination with qPCR and microarray analysis of total and active functional genes targeting archaeal amoA and nirS as marker genes for nitrification and denitrification, respectively. Denitrification was responsible for the highest N2O production with mean 8.7 nmol L-1 d-1 but up to 118 ± 27.8 nmol L-1 d-1 just below the oxic-anoxic interface. Highest N2O production from AO of 0.16 ± 0.003 nmol L-1 d-1 occurred in the upper oxycline at O2 concentrations of 10 - 30 µmol L-1 which coincided with highest archaeal amoA transcripts/genes. Oxygen responses of N2O production varied with substrate, but production and yields were generally highest below 10 µmol L-1 O2. Particulate organic matter additions increased N2O production by denitrification up to 5-fold suggesting increased N2O production during times of high particulate organic matter export. High N2O yields from ammonium oxidation of 2.1% were measured, but the overall contribution to N2O production stays an order of magnitude behind denitrification as an N2O source. Hence, these findings show that denitrification is the most important N2O production process in low oxygen conditions fueled by organic carbon supply which implies a positive feedback of the total oceanic N2O sources in response to increasing oceanic deoxygenation. [SUBMITTER_CITATION]: Frey, C., Bange, H. W., Achterberg, E. P., Jayakumar, A., Löscher, C. R., Arévalo-Martínez, D. L., León-Palmero, E., Sun, M., Sun, X., Xie, R. C., Oleynik, S., and Ward, B. B.: Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru, Biogeosciences, 17, 2263-2287
Project description:An essential interaction between sunlight and eukaryotes involves the production of vitamin D through exposure to ultraviolet (UV) radiation. While extensively studied in vertebrates, the role of vitamin D in non-animal eukaryotes like microalgae remains unclear. To investigate the potential involvement of vitamin D in the response of microalgae to UV, we focus on Emiliania huxleyi, a microalga found in shallow ocean depths that are exposed to UV radiation. Our results show that E. huxleyi algae produce vitamin D2 and D3 in response to UV irradiation. We further demonstrate that E. huxleyi algae respond to external administration of vitamin D at the transcriptional level, regulating the expression of protective mechanisms that are also regulated in response to UV. Our data reveal that addition of vitamin D enhances the algal photosynthetic performance while reducing harmful reactive oxygen species buildup. This study contributes to understanding the function of vitamin D in E. huxleyi and sheds light on its role in non-animal eukaryotes, as well as its potential importance in marine ecosystems.
Project description:Ammonia-oxidizing archaea (AOA) have been reported at high abundance in much of the global ocean, even in environments such as pelagic oxygen minimum zones (OMZs), where conditions seem unlikely to support aerobic ammonium oxidation. Due to the lack of information on any potential alternative metabolism of AOA, the AOA community composition might be expected to differ between oxic and anoxic environments, indicating some difference in ecology and/or physiology of the AOA assemblage. This hypothesis was tested by evaluating AOA community composition using a functional gene microarray that targets the ammonia monooxygenase gene subunit A (amoA). The relationship between environmental parameters and the biogeography of the Arabian Sea and the Eastern Tropical South Pacific (ETSP) AOA assemblages was investigated using principal component analysis (PCA) and redundancy analysis (RDA). In both the Arabian Sea and the ETSP, AOA communities within the core of the OMZ were not significantly different from those inhabiting the oxygenated surface waters above the OMZ. The AOA communities in the Arabian Sea were significantly different from those in the ETSP. In both oceans, the abundance of archaeal amoA gene in the core of the OMZ was higher than that in the surface waters. Our results indicate that AOA communities are distinguished by their geographic origin. RDA suggested that temperature was the main factor that correlated with the differences between the AOA communities from the Arabian Sea and those from the ETSP. Physicochemical properties that characterized the different environments of the OMZ and surface waters played a less important role than did geography in shaping the AOA community composition.
Project description:Marine microbial communities from expanding oxygen minimum zones in Line P, North Pacific Ocean - Metatranscriptome Pilot_A09P20_1000m
Project description:Marine microbial communities from expanding oxygen minimum zones in Line P, North Pacific Ocean - Metatranscriptome Pilot_J09P20_1000m