Project description:Biotechnology suggests that microorganisms can be used as chemical factories that transform renewable feedstock into value-added chemicals. Conversion of glycerol, using direct transformation or fermentation, into valuable products such as polymers, surfactants, solvents, and chemical intermediates has attained growing interest in recent years due to the dramatic growth of the biodiesel industry. However, the use of cell factories could be limited by low growth and uptake rates under certain environmental conditions, thus understanding microbial nutritional requirements is a critical point to use them as cell factories. Here, we compared E. coli ATCC 8739 transcriptomic responses to glycerol under aerobic conditions in an optimized culture medium (Condition 3) and one evolved strain in glycerol using as a reference a glycerol-based medium (Condition 11). Our analyses revealed 478 and 431 differentially expressed genes (DEGs) with log2 fold change (FC) > |2| and p Adjusted value < 0.05, for the bacteria growing in the optimized culture medium and the evolved strain, respectively. Among the DEGs, glp operon was found to be up-regulated as a response to glycerol uptake. Interestingly, between them, it was found genes that requires the use of phosphorous to ovoid the toxicity during glycerol consumption. Previously, we identified using a computational approach that phosphorous and nitrogen are essential compound that support high glycerol consumption in E. coli.
Project description:Rsf1p is a putative transcription factor required for efficient growth using glycerol as sole carbon source but not for growth on the alternative respiratory carbon source ethanol. We use microarrays to determine the differences in the transcriptional program between the Δrsf1 mutant and the wild type during respiratory growth on glycerol as well as the transition to growth on glycerol as sole carbon source. Keywords: Mutant analysis during timecourse following switching carbon source from dextrose to glycerol
Project description:Laboratory adaptive evolution experiments were conducted using serial passage of E. coli in M9 minimal medium supplemented with either 2 g/L of lactate for 60 days or 2 g/L of glycerol for 44 days. 7 parallel evolution strains were generated for growth on lactate and 7 parallel evolution strains were generated for growth on glycerol. Affymetrix arrays were used to study the time-course change in gene expression from unevolved E. coli (day 0) to a midpoint evolved strain (day 20) and evolutionary endpoints
Project description:Rsf1p is a putative transcription factor required for efficient growth using glycerol as sole carbon source but not for growth on the alternative respiratory carbon source ethanol. We use microarrays to determine the differences in the transcriptional program between the delta-rsf1 mutant and the wild type during respiratory growth on glycerol as well as the transition to growth on glycerol as sole carbon source. Experiment Overall Design: delta-rsf1or the isogenic parent strain were grown to early log (A600=0.6) in YPD and then washed twice in prewarmed YPG (30 C) and returned to the air shaker in YPG for 15, 30 or 60 minutes. "Limit" conditions were provided by harvesting cells grown in YPD to early log phase without shifting to YPG and by harvesting cells grown in YPG to early log phase. Since the delta-rsf1 mutant and its isogenic parent strain grow equally well on the respiratory carbon source ethanol, cells were also harvested after being grown in ethanol to early log phase.
Project description:Laboratory adaptive evolution experiments were conducted using serial passage of E. coli in M9 minimal medium supplemented with either 2 g/L of lactate for 60 days or 2 g/L of glycerol for 44 days. 7 parallel evolution strains were generated for growth on lactate and 7 parallel evolution strains were generated for growth on glycerol. Affymetrix arrays were used to study the time-course change in gene expression from unevolved E. coli (day 0) to a midpoint evolved strain (day 20) and evolutionary endpoints Biological replicate arrays were conducted for each of the time points tested for the different evolution strains
Project description:Adaptation to altered osmotic conditions is a fundamental property of living cells and has been studied in particular detail in the yeast Saccharomyces cerevisiae. Yeast cells accumulate glycerol as compatible solute, controlled at different levels by the High Osmolarity Glycerol (HOG) response pathway. Up to now, essentially all osmostress studies in yeast have been performed with glucose as carbon and energy source, which is metabolised by glycolysis with glycerol is as a normal by-product. Here we investigated the response of yeast to osmotic stress when yeast is respiring ethanol as carbon and energy source. Remarkably, yeast cells do not accumulate glycerol under these conditions and it appears that trehalose may partly take over the role as compatible solute. The HOG pathway is activated in very much the same way as in during growth on glucose medium and is also required for osmotic adaptation. Slower volume recovery was observed in ethanol-grown cells as compared to glucose-grown cells. Dependence on key regulators as well as the global gene expression profile were similar in many ways to those previously observed in glucose-grown cells. However, there are indications that cells re-arrange redox-metabolism when respiration is hampered under osmostress, a feature that could not be observed in glucose-grown cells.
Project description:Gas-fermenting acetogens, such as Clostridium autoethanogenum, have emerged as promising biocatalysts capable of converting CO and CO2-containing gases into fuels and chemicals relevant for a circular economy. However, functionalities of the majority of genes in acetogens remain uncharacterised, hindering the development of acetogen cell factories through targeted genetic engineering. We previously identified gene targets through adaptive laboratory evolution (ALE) that potentially realise enhanced autotrophic phenotypes in C. autoethanogenum. In this study, we deleted one of the targets – CLAU_0471 (proposed amino acid permease) – with high mutation occurrence in ALE isolates and extensively characterised autotrophic growth of strain RE3 in batch bottle and bioreactor continuous cultures. In addition, we characterized two previously reverse-engineered strains RE1 (deletion of CLAU_3129; putative sporulation transcriptional activator Spo0A) and RE2 (SNP in CLAU_1957; proposed two component transcriptional regulator winged helix family). Strikingly, the strains recovered the superior phenotypes of ALE isolates, including faster autotrophic growth, no need for yeast extract, and robustness in bioreactor operation (e.g. low sensitivity to gas ramping, high biomass, and dilution rates). Notably, RE3 exhibited elevated 2,3-butanediol production while RE1 performed similar to the best-performing previously characterised ALE isolate LAbrini. The three reverse-engineered strains showed similarities in proteome expression and bioinformatic analyses suggest that the targeted genes may be involved in overlapping regulatory networks. Our work provides insights into genotype-phenotype relationships for a better understanding of the metabolism of an industrially-relevant acetogen.