Genome-scale CRISPRi screen identifies pcnB repression conferring improved physiology for overproduction of free fatty acids in Escherichia coli II
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ABSTRACT: Microbial physiology plays a pivotal role in construction of a superior microbial cell factory for efficient production of desired products. Here we identified pcnB repression through genome-scale CRISPRi modulation combining fluorescence-activated cell sorting (FACS) and next-generation sequencing (NGS), which confers improved physiology for free fatty acids (FFAs) overproduction in Escherichia coli. The repression of pcnB could improve the stability and abundance of the transcripts involved in proton-consuming system, conferring a global improvement on cell membrane, redox state, and energy level. These physiological advantages facilitated further identification of acrD repression enhancing FFAs efflux. The engineered strain pcnBi-acrDi-fadR+ achieved 35.1 g l−1 FFAs production in fed-batch fermentation, which is the maximum titer in E. coli reported to date. This study underscores the significance of hidden genetic determinants in microbial biosynthesis and sheds light on the role of microbial physiologies in boosting microbial biosynthesis.
ORGANISM(S): Escherichia coli str. K-12 substr. MG1655
Project description:Microbial physiology plays a pivotal role in construction of a superior microbial cell factory for efficient production of desired products. Here we identified pcnB repression through genome-scale CRISPRi modulation combining fluorescence-activated cell sorting (FACS) and next-generation sequencing (NGS), which confers improved physiology for free fatty acids (FFAs) overproduction in Escherichia coli. The repression of pcnB could improve the stability and abundance of the transcripts involved in proton-consuming system, conferring a global improvement on cell membrane, redox state, and energy level. These physiological advantages facilitated further identification of acrD repression enhancing FFAs efflux. The engineered strain pcnBi-acrDi-fadR+ achieved 35.1 g l−1 FFAs production in fed-batch fermentation, which is the maximum titer in E. coli reported to date. This study underscores the significance of hidden genetic determinants in microbial biosynthesis and sheds light on the role of microbial physiologies in boosting microbial biosynthesis.
Project description:In this study, we carried out genome-scale CRISPRi modulation combining fluorescence-activated cell sorting (FACS) and next-generation sequencing (NGS) to identify genetic determinants for FFAs overproduction in Escherichia coli. The pcnBi (AP) strain that repressed the expression of pcnB produced 2992 mg l FFAs, which was 4.0-fold of the CF (A) strain. To analyze the underlying mechanism of FFAs overproduction, the engineered strain pcnBi and the control strain CF were applied to the transcriptomic and proteomic analyses.
Project description:Genome-scale CRISPRi screen identifies pcnB repression conferring improved physiology for overproduction of free fatty acids in Escherichia coli II
Project description:The experiments were aimed at comparison of gene expression patterns of Escherichia coli pcnB mutant (IBPC903) lacking functional poly(A) polymerase I with its isogenic wild-type (N3433) strain grown in Luria-Bertani (LB) by using custom microarrays with improved detection of E. coli sRNAs.
Project description:We employ omics analyses to identify potential targets in multiple cellular processes, enabling systematical discovery of beneficial chromosomal gene targets that can be engineered to optimize free fatty acids (FFAs) production in Escherichia coli. As a result, we identify 56 beneficial genes , including 46 novel targets functioning in cell structure and division, and signaling transduction that efficiently facilitate FFAs production.
Project description:The only membrane-anchored and essential ATP-dependent protease in Escherichia coli is FtsH. It controls the intracellular concentration of the deacetylase LpxC, which catalyses the first committed step in lipopolysaccharide biosynthesis. LpxC stability is strictly regulated in a growth rate-dependent manner to ascertain a vital equilibrium of lipopolysaccharide (LPS) and phospholipid biosynthesis. Previous studies suggested the involvement of yet unknown factors in LpxC degradation. Aiming at the identification of such factors that are predicted to be associated with LpxC and/or FtsH at high and low growth rates, we established a quantitative super-SILAC LC-MS/MS-based approach. The identification of known LpxC and FtsH interactors validated our approach. Several enzymes involved in fatty acid biosynthesis and degradation, including the central regulator FadR, interacted with LpxC and/or FtsH and showed a significant impact on LpxC stability. The newly identified LpxC and FtsH interactor WaaH, a LPS-modifying enzyme, stimulates LpxC degradation. Our results go beyond the previously established link between LPS and phospholipid biosynthesis and uncover a far-reaching network that controls LPS biosynthesis by involving multiple enzymes in fatty acid metabolism and phospholipid biosynthesis and modification.
Project description:To unravel the regulon of FadR (Saci_1107), comparative transcriptomic analysis was performed for the fadR deletion mutant versus the isogenic WT strain using RNA-seq approach.
Project description:To unravel the regulon of FadR (Saci_1107) , comparative transcriptomic analysis was performed for the fadR deletion mutant versus the isogenic WT strain using RNA-seq approach.
Project description:To investigate the extent of the effect of poly(A) polymerase (PAP I)-mediated polyadenylation on RNA stability, we performed the first genome-wide study of RNA stability in the absence of PAP I activity. Inactivation of the pcnB gene coding for PAP I led to a global stabilization of E. coli RNAs, with 1403 stabilized transcripts and only 4 destabilized. Stabilized RNAs were involved in essential cellular functions such as DNA replication and repair, translation, RNA degradation, central carbon metabolism but also in stress responses. Because PAP I is an ATP-consuming enzyme we wondered whether the RNA stabilization observed after inactivation of PAP I could also be related to changes in intracellular ATP levels. We demonstrated for the first time in E. coli, that lowering intracellular ATP levels below 1 µM/OD stabilizes RNAs. Although the ATP level was reduced by 20 % in the pcnB mutant on glucose, the ATP level was still too high to have any role in the observed RNA stabilization. However, in experiments where the ATP level was artificially strongly decreased, inactivation of PAP I by substrate availability was implicated in the stabilization mechanism of certain RNAs. This study clearly demonstrates that PAP I is at the crossroads of the regulation of RNA stability by energy status in E. coli cells.