Dataset Information

Systems biology analysis of Zymomonas mobilis ZM4 ethanol stress responses.

ABSTRACT:

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.

SUBMITTER: Yang S

PROVIDER: S-EPMC3712917 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Systems biology analysis of Zymomonas mobilis ZM4 ethanol stress responses.

Yang Shihui S Pan Chongle C Tschaplinski Timothy J TJ Hurst Gregory B GB Engle Nancy L NL Zhou Wen W Dam Phuongan P Xu Ying Y Rodriguez Miguel M Dice Lezlee L Johnson Courtney M CM Davison Brian H BH Brown Steven D SD

PloS one 20130716 7

<h4>Background</h4>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.<h4>Methodology/principal findings</h4>In this study, ethanol stress responses were investigated using systems biology ap ...[more]

PMID: 23874800

Similar Datasets

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:Background: Growth in the global population and industrial activities has increased world energy consumption. Bioethanol is considered as an alternative renewable energy source. Among various ethanol-producing microbes, Zymomonas mobilis ZM4 has received special attention due to its higher ethanol yield and tolerance. Advances in genetic engineering are particularly important for developing microorganisms with improved ethanol production. However, the variety of factors involved in the response to high concentrations of ethanol makes it difficult to devise genetic engineering strategies to generate alcohol tolerant strains. For a better understanding of the ethanol tolerance phenomenon, we obtained and characterized two Z. mobilis ZM4 mutants (ER79ap and ER79ag) with increased ethanol tolerance. Results: Mutants were obtained using a strain adaptive evolution method in mini-fermentors and sequential transfers to higher ethanol concentrations. Mutations were identified by Illumina genomic sequencing. Strain ER79ap possesses three point mutations in the following genes: SpoT/RelA, which synthesizes and degrades the alarmone ppGpp; clpB, encoding a disgregase; and clpP, a component of the Clp protease. In contrast, strain ER79ag has four mutations in the subsequent genes: spoT/relA; rimO; clpP; and in a gene encoding a hypothetical protein with a CBS domain. Transcript profiles of ZM4 and ER79ap were obtained with microarray analysis and identified 126 genes in ZM4 and 148 genes in ER79ap that were differentially expressed in response to ethanol. Conclusions: Both mutants carry mutations in clpP and relA/spoT genes, suggesting that these genes are responsible of their enhanced ethanol tolerance. Transcript profile analysis of the ZM4 and ER79ap showed that they share a set of forty genes that are differentially expressed under ethanol stress and this set may correspond to those that are crucial for the ethanol response. The expression profiles indicate that ethanol induces a major reprograming of transcription that involves changes in the cell membrane, protein synthesis, and in some metabolic pathways, especially those involved in the amino acid metabolism. Our data suggest that clpP and in particular the relA/spoT gene can be targets for bioengineering ethanol tolerance.

Project description:Zymomonas mobilis ZM4 produces near theoretical yields of ethanol with high specific productivity and recombinant strains are able to ferment both C-5 and C-6 sugars. However, the genetic and physiological basis of the ZM4 response to various industrially-relevant stresses is poorly understood. In this study, the dynamics of ZM4 oxygen stress responses were elucidated by characterizing the transcriptomic and metabolomic profiles of aerobic and anaerobic fermentations using whole-genome microarray analysis and gas chromatography-mass spectrometry. In the absence of oxygen, ZM4 consumed glucose more rapidly, had a higher growth rate, and ethanol was the major end-product. Under aerobic conditions, much less ethanol was observed with other end-products produced, including acetate, lactate, and acetoin. In the early exponential phase, no genes were detected as being significantly differentially expressed between aerobic and anaerobic conditions via microarray analysis. However, microarray analysis of the stationary phase cultures revealed that 166 genes were significantly differentially expressed by more than two-fold. Quantitative-PCR validated the expression values for seventeen genes from different categories of stationary phase microarray data. Transcripts for Entner-Doudoroff pathway genes and gene pdc, encoding a key enzyme leading to the ethanol production, were at least 30-fold more abundant under anaerobic conditions at stationary phase based on quantitative-PCR results. Expression of stress response genes was found to be greater under oxygen stress conditions. GC-MS analysis of stationary phase intracellular metabolites indicated that ZM4 under anaerobic conditions contained lower levels of amino acids, glucose and ED pathway intermediates, whereas metabolites such as ribitol, trehalose, myristic acid, glyceric acid, glucose 6-phosphate, mannose 6-phosphate, and 4-hydroxybutanoic acid were more abundant than under aerobic conditions. Transcriptomic and metabolomic data were consistent with faster glucose consumption and greater ethanol production under anaerobic conditions and suggested gene targets for deletion and improved fermentation. Keywords: Time course/ Stress Response

Dataset Information

Systems biology analysis of Zymomonas mobilis ZM4 ethanol stress responses.

Background

Methodology/principal findings

Conclusions

Publications

Systems biology analysis of Zymomonas mobilis ZM4 ethanol stress responses.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure