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:Using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) on microcosm samples from early phase plant litter degradation, we found that proteins and condensed hydrocarbons are the compounds with the strongest correlation to dissolved organic carbon (DOC) concentration. Proteins correlated positively with DOC concentration, while tannins and condensed hydrocarbons correlated negatively with DOC. With nuclear magnetic resonance (NMR) spectroscopy, we identified 15 individual compounds associated with DOC concentration. Through random forest, neural network, and indicator species analyses, we identified bacterial and fungal taxa associated with DOC concentration and additionally identified connections between microorganisms and DOC chemical composition.
Project description:In this study, we characterize the protein uptake and degradation pathways of S. cerevisiae to better understand its impact on protein secretion titers. We do find that S. cerevisiae can consume significant (g/L) quantities of whole proteins. Characterizing the systems with metabolomics and transcriptomics, we identify metabolic and regulatory markers that are consistent with uptake of whole proteins by endocytosis, followed by intracellular degradation and catabolism of substituent amino acids. Uptake and degradation of recombinant protein products may be common in S. cerevisiae protein secretion systems, and the current data should help formulate strategies to mitigate product loss.
Project description:Because of severe abiotic limitations, Antarctic soils represent simplified ecosystems, where microorganisms are the principle drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report a number of highly consistent changes in microbial community structure and abundance across very disparate sub-Antarctic and Antarctic environments following three years of experimental field warming (+ 0.5-2°C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio. These alterations were linked to a significant increase in soil respiration. Furthermore, the shifts toward generalist or opportunistic bacterial communities following warming weakened the linkage between bacterial diversity and functional diversity. Warming also increased the abundance of some organisms related to the N-cycle, detected as an increase in the relative abundance of nitrogenase genes via GeoChip microarray analyses. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures, thereby potentially disrupting soil functioning.
Project description:In this study, we characterize the protein uptake and degradation pathways of S. cerevisiae to better understand its impact on protein secretion titers. We do find that S. cerevisiae can consume significant (g/L) quantities of whole proteins. Characterizing the systems with metabolomics and transcriptomics, we identify metabolic and regulatory markers that are consistent with uptake of whole proteins by endocytosis, followed by intracellular degradation and catabolism of substituent amino acids. Uptake and degradation of recombinant protein products may be common in S. cerevisiae protein secretion systems, and the current data should help formulate strategies to mitigate product loss. Saccharomyces cerevisiae strains at different cultivation conditions were selected at early glucose phase in batch fermentations for RNA extraction and hybridization on Affymetrix microarrays. Biological triplicates were applied, and strains growing at normal conditions (with no BSA supplemented) were used as the control strain.
Project description:The purpose of this project was to quantify the exchange of thiamine between bacteria and algae. We previously observed that the model bacteria, Escherichia coli, enhanced the growth and substrate uptake of the green algae, Auxenochlorella protothecoides. We hypothesized that this growth enhancement was due to the secretion of thiamine derivatives or degradation products by E. coli followed by uptake of these compounds by A. protothecoides. Targeted and untargeted LCMS revealed the presence of thiamine dervatives in E. coli cell extracts. These LCMS methods were also used to quantify thiamine derivatives and two degradation products, HMP and THZ, present in E. coli medium after cell removal. The LCMS results along with culture studies were employed to show that thiamine derivatives and degradation products were the primary mechanism of symbiosis between E. coli and A. protothecoides.
Project description:The purpose of this project was to quantify the exchange of thiamine between bacteria and algae. We previously observed that the model bacteria, Escherichia coli, enhanced the growth and substrate uptake of the green algae, Auxenochlorella protothecoides. We hypothesized that this growth enhancement was due to the secretion of thiamine derivatives or degradation products by E. coli followed by uptake of these compounds by A. protothecoides. Targeted and untargeted LCMS revealed the presence of thiamine dervatives in E. coli cell extracts. These LCMS methods were also used to quantify thiamine derivatives and two degradation products, HMP and THZ, present in E. coli medium after cell removal. The LCMS results along with culture studies were employed to show that thiamine derivatives and degradation products were the primary mechanism of symbiosis between E. coli and A. protothecoides.
Project description:Because of severe abiotic limitations, Antarctic soils represent simplified ecosystems, where microorganisms are the principle drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report a number of highly consistent changes in microbial community structure and abundance across very disparate sub-Antarctic and Antarctic environments following three years of experimental field warming (+ 0.5-2°C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio. These alterations were linked to a significant increase in soil respiration. Furthermore, the shifts toward generalist or opportunistic bacterial communities following warming weakened the linkage between bacterial diversity and functional diversity. Warming also increased the abundance of some organisms related to the N-cycle, detected as an increase in the relative abundance of nitrogenase genes via GeoChip microarray analyses. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures, thereby potentially disrupting soil functioning. We conducted in situ warming experiments for three years using open-top chambers (OTCs) at one sub-Antarctic (Falkland Islands, 52ºS) and two Antarctic locations (Signy and Anchorage Islands, 60ºS and 67ºS respectively) (see Supplementary Fig. 1 for a map). OTCs increased annual soil temperature by an average of 0.8°C (at a depth of 5 cm), resulting in 8-43% increase in positive-degree days annually and a decrease in freeze-thaw cycle frequency by an average of 15 cycles per year (8). At each location, we included densely vegetated and bare fell-field soils in the experimental design for a total of six environments. Densely vegetated and bare environments represent two contrasting environments for Antarctic soil microorganisms, with large differences in terms of C and N inputs to soils. Massively parallel pyrosequencing (Roche 454 GS FLX Titanium) of 16S rRNA gene amplicons was used to follow bacterial diversity and community composition [GenBank Accession Numbers: HM641909-HM744649], and functional gene microarrays (GeoChip 2.0)(11) were used to assess changes in functional gene distribution. Bacterial and fungal communities were also quantified using real-time PCR.