Project description:In this study we examined an anaerobic digester reactor fed with cellulose in order to identify cellulose degrading microorganisms using a culture independent approach. A metagenome was linked to the newly synthesized proteins involved by cellulose, by investigation of labelled proteins (Protein-SIP). The study aims at identifying microorganisms involved in the degradation of plant-based biomass.
Project description:Native mass spectrometry (MS) has become an important technique in several fields including structural biology and drug discovery, due to its ability to study non-covalent assemblies in the gas phase. In many settings, the main drawbacks of native MS are the incompatibility of electrospray ionisation with non-volatile salts and the risk of protein signal suppression if small, efficiently ionising molecules are present in the sample. This often requires an offline buffer exchange step and/or parallel sample preparation workflow to other analytical methods, reducing both the adoption and the throughput of native MS. Here, we exploit the dynamics of analytes flowing through an open tubular capillary to keep molecules with a small hydrodynamic radius (e.g., salts) inside a Taylor dispersion regime, while pushing larger species (e.g., proteins) into a non-Taylor regime. The result of this is that the larger species elute earlier, and are effectively buffer exchanged within the capillary on a timescale of approximately 30 seconds. In addition to desalting of proteins injected in solutions containing 25 to 200 mM NaCl and other biologically relevant buffers (e.g., HEPES, TCEP, and glycerol), we also demonstrate that this method can separate unbound small molecules from protein-ligand complexes, enabling rapid, multiplexed ligand screening based on native MS. Finally, we investigated the dependence of the critical flow rate required to push proteins outside the Taylor regime on protein size, enabling limited size-based separation of proteins and providing a starting point for others to adopt this method. Taylor/non-Taylor dispersion mass spectrometry (TNT-MS) was implemented using an unmodified LC-MS system operated without a chromatographic column and coupled to an autosampler. This allows significant automation, which we believe will contribute to the wider adoption of native MS as a routine method.
Project description:In large-scale production processes, metabolic control is typically achieved by limited supply of essential nutrients like ammonia. With increasing bioreactor dimensions, microbial producers such as Escherichia coli are exposed to changing substrate availabilities due to limited mixing. In turn, cells sense and respond to these dynamic conditions leading to frequent activation of their regulatory programs which result in production yield losses. This study is focused on transcriptional changes due to fluctuating ammonia supply, while sampling a continuously running two-compartment bioreactor system comprising a stirred tank reactor (STR) and a plug flow reactor (PFR). A previously created mutant E.coli SR was used to limit the reaction to environmntal influences via knock-out of stringent response. E. coli WT revealed highly diverging short-term transcriptional responses in ammonia fluctuation compared E. coli SR.
Project description:A continuous culture of Bifidobacterium longum NCC2705 was carried out in a 2.5-l reactor (Bioengineering AG, Wald, Switzerland), equipped with a Biospectra control system (Biospectra AG, Schlieren, Switzerland) and containing 2 l of MRS, added of 0.05% cysteine, inoculated with 2 % (v/v) preculture. The temperature was maintained at 37°C and the pH at 6.0 by addition of 5 M NaOH. The culture was stirred constantly at 250 rpm using two rushton type propellers. Anaerobic conditions were maintained by flushing the headspace of the reactor with CO2. After 8 h in batch mode the culture was run in continuous mode at a dilution rate of 0.1 h-1. Fresh medium was added using a peristaltic pump (Alitea, Bioengineering AG, Wald, Switzerland), and fermented broth harvested with a second peristaltic pump (Alitea, Bioengineering AG, Wald, Switzerland) set at a slightly higher flow rate. A stabilization period of 90 h (corresponding to nine reactor volume changes) was operated prior culture monitoring (t=0). Aliquots of 2 ml taken at t=31, 134 and 211 h were centrifuged (4,000 g, 1 min, room temperature) for transcriptomic analysis. Supernatants were discarded and cell pellets snap frozen in liquid nitrogen and stored at -80ºC until RNA-extraction. Keywords: Time course of Bifidobacterium longum in continuous culture
Project description:In large-scale production processes, metabolic control is typically achieved by limited supply of essential nutrients like glucose or ammonia. With increasing bioreactor dimensions, microbial producers such as Escherichia coli are exposed to changing substrate availabilities due to limited mixing. In turn, cells sense and respond to these dynamic conditions leading to frequent activation of their regulatory programs. Previously, we characterized short- and long-term strategies of cells to adapt to glucose fluctuations. Here, we focused on fluctuating ammonia supply, while studying a continuously running two-compartment bioreactor system comprising a stirred tank reactor (STR) and a plug flow reactor (PFR). Genes were repeatedly switched on/off when E. coli returned to the STR. Moreover, E. coli revealed highly diverging long-term transcriptional responses in ammonia compared to glucose fluctuations. The identification of target genes may help to create robust cells and processes for large-scale application.
Project description:Mass spectrometry-based analysis of trace analytes, such as the single cell proteome, benefit from operation at low flow rates (i.e., <50 nL/min). However, the standard high-pressure binary pumps needed to achieve these flow rates are not commercially available, requiring splitting of the gradient flow to achieve low-nanoliter-per-minute flow rates, which wastes solvent and can lead to flow inconsistencies. To address this, we have created a new method for creating gradients by combining plugs of mobile phase of increasing solvent strength together in a column and then using Taylor dispersion to form the desired smooth gradient profile. Additionally, our method dramatically reduces costs, as only a single isocratic high-pressure pump is required. Following optimization of gradient shapes using UV absorption for both 10- and 20-min active gradients, we measured 200 pg injections of HeLa digest on a timsTOF Ultra mass spectrometer in DIA mode. We then investigated differences in protein expression between single cells originating from two different colonies of ATG-knockout HeLa cells. Thousands of proteins were quantified, and a potential mechanism explaining differential immune responses of these two colonies upon exposure to viral DNA treatment was determined.