Project description:Investigation of the expression profiling of the ethanologenic Zymomonas mobilis in response to ethanol stress. A six chip study using total RNA recovered from three separate wild-type cultures of Zymomonas mobilis ATCC31821 and three separate cultures of a triple treated with 5% ethanol. Each chip measures the expression level of 1800 genes from Zymomonas mobilis ATCC31821 and the associated plasmids, with three-fold technical redundancy.
Project description:Investigation of the expression profiling of the ethanologenic Zymomonas mobilis in response to furfural stress. A six chip study using total RNA recovered from three separate wild-type cultures of Zymomonas mobilis ATCC31821 and three separate cultures of a triple treated with 1.0 g/l furfural. Each chip measures the expression level of 1800 genes from Zymomonas mobilis ATCC31821 and the associated plasmids, with three-fold technical redundancy.
Project description:Previously we found that modified Zymomonas mobilis is able to convert glucose to ethanol when fermenting highly concentrated hydrolysates such as 9% glucan-loading AFEX-pretreated corn stover hydrolysate (ACSH), but that xylose conversion after glucose depletion is greatly impaired. We hypothesized that impaired xylose conversion is caused by lignocellulose-derived inhibitors (LDIs) present in highly concentrated hydrolysates. To investigate the effects of LDIs on xylose utilization in Z. mobilis, we generated synthetic hydrolysates (SynHs) that contains nutrients and LDI at concentrations found in authentic 9% ACSH. Comparative fermentations of Z. mobilis 2032 using SynH with or without LDI were performed, and samples were collected for endproduct, transcriptomic, metabolomic, and proteomic analyses. Our data suggest that the overall flux of xylose metabolism is reduced in the presence of LDIs. However, the expression of most genes involved in glucose and xylose assimilation was not affected by LDIs nor did we observe blocks in glucose and xylose metabolic pathways. Several LDI-specific effects were observed including intracellular accumulation of mannose-1P and mannose-6P, down regulation of a Type I secretion system (ZMO0252-0255), and upregulation of sulfur metabolism genes and the RND family efflux pump system (ZMO0282_0283_0285). This efflux pump system is involved in detoxification. Together, our findings identify cellular responses to LDIs and possible causes of impaired xylose conversion that will enable future strain engineering of Z. mobilis.
Project description:Background Zymomonas mobilis ZM4 is a capable ethanologenic bacterium with high ethanol productivity and ethanol tolerance. Previous studies indicated that several stress-related proteins and changes in the ZM4 membrane lipid composition may contribute to ethanol tolerance. However, the molecular mechanisms of its ethanol stress response have not been elucidated fully. Methodology/Principal Findings In this study, ethanol stress responses were investigated using systems biology approaches. Medium supplementation with an initial 47 g/L (6% v/v) ethanol reduced Z. mobilis ZM4 glucose consumption, growth rate and ethanol productivity compared to that of untreated controls. A proteomic analysis of early exponential growth identified about one thousand proteins, or approximately 55% of the predicted ZM4 proteome. Proteins related to metabolism and stress response such as chaperones and key regulators were more abundant in the early ethanol stress condition. Transcriptomic studies indicated that the response of ZM4 to ethanol is dynamic, complex and involves many genes from all the different functional categories. Most down-regulated genes were related to translation and ribosome biogenesis, while the ethanol-upregulated genes were mostly related to cellular processes and metabolism. Transcriptomic data were used to update Z. mobilis ZM4 operon models. Furthermore, correlations among the transcriptomic, proteomic and metabolic data were examined. Among significantly expressed genes or proteins, we observe higher correlation coefficients when fold-change values are higher. Conclusions Our study has provided insights into the responses of Z. mobilis to ethanol stress through an integrated “omics” approach for the first time. This systems biology study elucidated key Z. mobilis ZM4 metabolites, genes and proteins that form the foundation of its distinctive physiology and its multifaceted response to ethanol stress. A sixteen array study using total RNA recovered from wild-type cultures of Zymomonas mobilis subsp mobilis ZM4 at different time points of 6, 10, 13.5, and 26h post-inoculation with 6% (v/v) treatment compred to that of control without ethanol supplementation. Two biological replicates for treatment and control condition.
Project description:we aimed to screen candidate kinase genes under the stress of phenolic aldehydes during ethanol fermentation for Zymomonas mobilis ZM4
Project description:High-resolution “tiling” expression data for Zymomonas mobilis ZM4 growing in rich and minimal media, heat-shocked, or at high ethanol
Project description:Zymomonas mobilis is an aerotolerant anaerobe and prolific ethanologen with attractive characteristics for industrial biofuel production. Here, we examine the effect of oxygen exposure on metabolism and gene expression in Z. mobilis by combining targeted metabolomics, mRNA sequencing, and shotgun proteomics. We found that exposure to oxygen profoundly influenced metabolism, inducing both transient metabolic bottlenecks and long-term metabolic remodeling. In particular, oxygen induced a severe but temporary metabolic bottleneck in the methyl erythritol 4-phosphate pathway for isoprenoid biosynthesis, likely caused by oxidative damage to the iron-sulfur co-factors of the final two enzymes of the pathway. This bottleneck was resolved with minimal changes in expression level of enzymes in the pathway but pronounced upregulation of enzymes related to iron-sulfur cluster maintenance and biogenesis (i.e. flavodoxin reductase and the suf operon). We also detected prominent changes in glucose utilization under aerobic conditions. Specifically, we observed increased gluconate production following exposure to oxygen, accounting for 18% of glucose uptake after 24 hours of aerobic growth. Our results suggest that under aerobic conditions, electrons from the oxidation of glucose to gluconate are delivered to the electron transport chain to minimize oxidative damage by reducing reactive oxygen species such as H2O2. This model is supported by the simultaneous upregulation of three membrane-bound dehydrogenases, cytochrome c peroxidase, and a cytochrome bd terminal oxidase.