Integrated OMICS guided engineering of biofuel butanol-tolerance in photosynthetic Synechocystissp. PCC 6803

Abstract

BackgroundPhotosynthetic cyanobacteria have been recently proposed as a ‘microbial factory’ to produce butanol due to their capability to utilize solar energy and CO2 as the sole energy and carbon sources, respectively. However, to improve the productivity, one key issue needed to be addressed is the low tolerance of the photosynthetic hosts to butanol.ResultsIn this study, we first applied a quantitative transcriptomics approach with a next-generation RNA sequencing technology to identify gene targets relevant to butanol tolerance in a model cyanobacterium Synechocystis sp. PCC 6803. The results showed that 278 genes were induced by the butanol exposure at all three sampling points through the growth time course. Genes encoding heat-shock proteins, oxidative stress related proteins, transporters and proteins involved in common stress responses, were induced by butanol exposure. We then applied GC-MS based metabolomics analysis to determine the metabolic changes associated with the butanol exposure. The results showed that 46 out of 73 chemically classified metabolites were differentially regulated by butanol treatment. Notably, 3-phosphoglycerate, glycine, serine and urea related to general stress responses were elevated in butanol-treated cells. To validate the potential targets, we constructed gene knockout mutants for three selected gene targets. The comparative phenotypic analysis confirmed that these genes were involved in the butanol tolerance.ConclusionThe integrated OMICS analysis provided a comprehensive view of the complicated molecular mechanisms employed by Synechocystis sp. PCC 6803 against butanol stress, and allowed identification of a series of potential gene candidates for tolerance engineering in cyanobacterium Synechocystis sp. PCC 6803.

Microalgal Systems Biology Through Genome-Scale Metabolic Reconstructions for Industrial Applications

“…Quia et al attempted to analyze the overall protein expression changes in Synechocystis sp. in the resistance mechanism upon exposure to ethanol, hexane, and butanol (Qiao et al, 2012;Tian et al, 2013;Wegener et al, 2010;Zhu et al, 2013). These proteomic studies provided an overall view of complicated metabolic networks and serve as useful references for metabolic reconstructions.…”

A global network-based protocol for functional inference of hypothetical proteins in Synechocystis sp. PCC 6803

“…For each condition, cells were harvested at three time points (i.e., 24, 48 and 72 h) for transcriptomic analysis. For details regarding experimental design and quality control of the data, please refer to the previous publications (Huang et al, 2013;Liu et al, 2012;Qiao et al, 2013b;Wang et al, 2012;Zhu et al, 2013).…”

Advances in proteomics for production strain analysis

“…An initial proteomics analysis of butanol stress in Synechocystis highlighted multiple simultaneous pathways activating in response to the stress [28], was followed up by a transcriptome study [29]. Joint analysis of these data identified slr1037 as part of a butanol-specific paired signal transduction system .…”