Project description:Soil microorganisms act as gatekeepers for soil-atmosphere carbon exchange by balancing the accumulation and release of soil organic matter. However, poor understanding of the mechanisms responsible hinders the development of effective land management strategies to enhance soil carbon storage. Here we empirically test the link between microbial ecophysiological traits and topsoil carbon content across geographically distributed soils and land use contrasts. We discovered distinct pH-controls on microbial mechanisms of carbon accumulation. Land use intensification in low-pH soils that increased pH above a threshold (~ 6.2) lead to carbon loss through increased decomposition following alleviation of acid-retardation of microbial growth. However, loss of carbon with intensification in near neutral-pH soils was linked to decreased microbial biomass and reduced growth efficiency that was, in turn, related to tradeoffs with stress alleviation and resource acquisition. Thus, less intensive management practices in near neutral-pH soils have more potential for carbon storage through increased microbial growth efficiency; whereas, in acidic soils microbial growth is a bigger constraint on decomposition rates.
Project description:The response of soil microbial community to climate warming through both function shift and composition reorganization may profoundly influence global nutrient cycles, leading to potential significant carbon release from the terrain to the atmosphere. Despite the observed carbon flux change in northern permafrost, it remains unclear how soil microbial community contributes to this ecosystem alteration. Here, we applied microarray-based GeoChip 4.0 to investigate the functional and compositional response of subsurface (15~25cm) soil microbial community under about one year’s artificial heating (+2°C) in the Carbon in Permafrost Experimental Heating Research site on Alaska’s moist acidic tundra. Statistical analyses of GeoChip signal intensities showed significant microbial function shift in AK samples. Detrended correspondence analysis and dissimilarity tests (MRPP and ANOSIM) indicated significant functional structure difference between the warmed and the control communities. ANOVA revealed that 60% of the 70 detected individual genes in carbon, nitrogen, phosphorous and sulfur cyclings were substantially increased (p<0.05) by heating. 18 out of 33 detected carbon degradation genes were more abundant in warming samples in AK site, regardless of the discrepancy of labile or recalcitrant C, indicating a high temperature sensitivity of carbon degradation genes in rich carbon pool environment. These results demonstrated a rapid response of northern permafrost soil microbial community to warming. Considering the large carbon storage in northern permafrost region, microbial activity in this region may cause dramatic positive feedback to climate change, which is important and necessary to be integrated into climate change models.
Project description:Expression profile of E. coli BW25113 grown under standard laboratory atmosphere with a fine particulate matter (PM2.5) concentration of 17 mg m-3, under urban polluted atmosphere with a PM2.5 of 230 mg m-3 or under diesel exhaust atmosphere with a PM2.5 of 613 mg m-3. Expression profile of the diesel exhaust atmosphere-adapted E. coli strain T56-1 grown under diesel exhaust atmosphere.
Project description:The effect of sulfide stress on Desulfovibrio vulgaris Hildenborough (DvH) gene expression was determined by comparing the gene expression profiles of DvH under conditions in which sulfide was allowed to accumulate (high sulfide, average concentration 10 mM) against DvH cells grown under conditions in which sulfide was removed by continuous gassing (low sulfide, average concentration 1 mM). High sulfide significantly decreased the instantaneous growth rate constant and final cell density of the culture indicating a decreased bioenergetic fitness. Changes in gene expression caused by exposure to high sulfide were determined using full-genome DvH microarrays. The transcription of ribosomal protein-encoding genes was decreased, in agreement with the lower growth rate of DvH under high sulfide conditions. Interestingly, expression of the gene for DsrD, located downstream of the genes for dissimilatory sulfite reductase (DsrAB) was also strongly down-regulated. In contrast, the expression of many genes involved in iron accumulation, stress response and proteolysis, and chemotaxis were increased. This indicates that high sulfide represents a significant stress condition, in which the bioavailability of metals like iron may be lowered and in which proteins (e.g. metalloenzymes) may need to be refolded, or proteolytically degraded. Overall this leads to a reduced growth rate and less efficient biomass production with available resources. For each condition 2 unique biological samples were hybridized to 4 arrays that each contained duplicate spots. Genomic DNA was used as universal reference.
Project description:The effect of sulfide stress on Desulfovibrio vulgaris Hildenborough (DvH) gene expression was determined by comparing the gene expression profiles of DvH under conditions in which sulfide was allowed to accumulate (high sulfide, average concentration 10 mM) against DvH cells grown under conditions in which sulfide was removed by continuous gassing (low sulfide, average concentration 1 mM). High sulfide significantly decreased the instantaneous growth rate constant and final cell density of the culture indicating a decreased bioenergetic fitness. Changes in gene expression caused by exposure to high sulfide were determined using full-genome DvH microarrays. The transcription of ribosomal protein-encoding genes was decreased, in agreement with the lower growth rate of DvH under high sulfide conditions. Interestingly, expression of the gene for DsrD, located downstream of the genes for dissimilatory sulfite reductase (DsrAB) was also strongly down-regulated. In contrast, the expression of many genes involved in iron accumulation, stress response and proteolysis, and chemotaxis were increased. This indicates that high sulfide represents a significant stress condition, in which the bioavailability of metals like iron may be lowered and in which proteins (e.g. metalloenzymes) may need to be refolded, or proteolytically degraded. Overall this leads to a reduced growth rate and less efficient biomass production with available resources.
Project description:The potential of the earthworm Eisenia andrei to reduce soil methanogens, and thus methane emissions to the atmosphere, were assayed in a microcosm experiment. Soils were incubated for 2, 4 and 6 months. We measured microarray parameters (methanogenic diversity) at the start of incubation, as well as after 2, 4 and 6 months of incubation in microcosms with or without earthworms. Methanosarcina barkeri was the most abundant genus that was revealed by AnaeroChip in our experiment.
Project description:Stress response of Methylococcus capsulatus str.Bath toward hydrogen sulfide (H2S) was investigated via physiological study and transcriptomic profiling. M. capsulatus (Bath) can grow and tolerate up to 0.75%vol H2S in headspace. Vast change in pH suggests biological relevant sulfide oxidation. Dozens of H2S-sensitive genes were identified from comparison of cell transcriptome in different H2S concentrations. Mc sulfide quinone reductase (SQR) and persulfide dioxygenase were found to be active during sulfide detoxification. Moreover, xoxF, a novel lanthanide(Ln)-dependent methanol dehydrogenase (MDH) was overexpressed in H2S while mxaF, a calcium-dependent MDH, was down-regulated, and such MDH switch phenomenon is also well known to be induced by addition of lanthanide via an as-yet-unknown mechanism. Activities in quorum sensing and RND efflux pump also suggest their role in sulfide detoxification, and might provide insight on the xoxF/mxaF switch mechanism.
Project description:Arabidopsis thaliana cells contain different O-acetylserine(thiol)lyase (OASTL) enzymes that catalyze the biosynthesis of cysteine. Recently, we have deeply investigated about one of the minor OASTL-like protein located in the cytosol, named DES1, highlighting some important clues about its metabolic function. We have demonstrated that DES1 catalyzes the desulfuration of L-cysteine to sulfide plus ammonia and pyruvate, instead of the biosynthesis of Cys, and thus, is a novel L-cysteine desulfhydrase (EC 4.4.1.1). The functionality of DES1 is being revealed by the phenotype of the T-DNA insertion mutants des1-1 and des1-2. We have performed a comparative transcriptomic analysis on leaves of the des1-1 and Col-0 wild type plants grown for 30 days under long-day conditions. The normalized data from the replicates showed differential expression of 1614 genes in the des1-1 mutant, with 701 genes down-regulated and 913 genes up-regulated by more than twofold, with a False Discovery Rate (FDR) of < 0.05 and an intensity signal restriction of lgSignal >7. This des1-1 transcriptional profile show a strong alteration when compared to a previous comparative transcriptomic analysis performed on leaves of the des1-1 and Col-0 wild type plants grown for 20 days under identical long-day conditions (GSE 19244). We have also performed a comparative transcriptomic analysis on leaves of the des1-1 and Col-0 wild type plants grown for 20 days and treated with sodium sulfide for 10 additional days. The comparison of the transcriptional profile of des1-1+Na2S versus Col-0+Na2S clearly shows that exogenous sulfide reversed the transcriptional level differences between the mutant and the wild type to reach similar transcriptional patterns as the array GSE19244. Our results suggest a role of sulfide as transcriptional regulator in the des1-1 mutant background. Using the Affymetrix ATH1 GeneChips, we performed two comparative transcriptomic analyses on leaves of the des1-1 and Col-0 wild type plants grown on soil under long-day conditions. One was performed on plants grown for 30 days and the other on plants grown for 20 days and treated for 10 additional days with 200 mM Na2S. Three biological replicates were performed for each sample and hybridized to the chips. We made the comparison of des1-1 versus wild-type and des1-1+Na2S versus wild-type+Na2S to classify the differently expressed genes in the mutant plant.
Project description:Acinetobacter baumannii is an opportunistic nosocomial pathogen that is the causative agent of several serious infections in humans. Here, we investigate the response of A. baumannii toward sodium sulfide (Na2S), known to be associated with some biofilms at oxic/anoxic interfaces, as a model for how this major human pathogen manages sulfide homeostasis. These results reveal that A. baumannii encodes two persulfide‑sensing transcriptional regulators, a primary sigma54‑dependent transcriptional activator (FisR), and a secondary system controlled by the persulfide‑sensing repressor biofilm growth‑associated repressor (BigR) both of which regulate operons encoding for sulfide detoxification or transportation. In addition, sulfide induces an alternative cytochrome bd oxidase which is refractory to inhibition by H2S and represses importers of alternate sulfur sources. Lastly, our results suggest additional genes regulated by BigR beyond sulfide detoxification including genes associated with assembly of type 1 chaperone-usher pilus.