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Liu G, Chang H, Qiao Y, Huang K, Zhang A, Zhao Y, Feng Z. Profiles of Small Regulatory RNAs at Different Growth Phases of Streptococcus thermophilus During pH-Controlled Batch Fermentation. Front Microbiol 2021; 12:765144. [PMID: 35035386 PMCID: PMC8753986 DOI: 10.3389/fmicb.2021.765144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 11/05/2021] [Indexed: 12/02/2022] Open
Abstract
Small regulatory RNA (sRNA) has been shown to play an important role under various stress conditions in bacteria, and it plays a vital role in regulating growth, adaptation and survival through posttranscriptional control of gene expression in bacterial cells. Streptococcus thermophilus is widely used as a starter culture in the manufacture of fermented dairy products. However, the lack of reliable information on the expression profiles and potential physiological functions of sRNAs in this species hinders our understanding of the importance of sRNAs in S. thermophilus. The present study was conducted to assess the expression profiles of sRNAs in S. thermophilus and to identify sRNAs that exhibited significant changes. A total of 530 potential sRNAs were identified, including 198 asRNAs, 135 sRNAs from intergenic regions, and 197 sRNAs from untranslated regions (UTRs). Significant changes occurred in the expression of 238, 83, 194, and 139 sRNA genes during the lag, early exponential growth, late exponential growth, and stationary phases, respectively. The expression of 14 of the identified sRNAs was verified by qRT-PCR. Predictions of the target genes of these candidate sRNAs showed that the primary metabolic pathways targeted were involved in carbon metabolism, biosynthesis of amino acids, ABC transporters, the metabolism of amino and nucleotide sugars, purine metabolism, and the phosphotransferase system. The expression of the predicted target genes was further analyzed to better understand the roles of sRNAs during different growth stages. The results suggested that these sRNAs play crucial roles by regulating biological pathways during different growth phases of S. thermophilus. According to the results, sRNAs sts141, sts392, sts318, and sts014 are involved in the regulation of osmotic stress. sRNAs sts508, sts087, sts372, sts141, sts375, and sts119 are involved in the regulation of starvation stress. sRNAs sts129, sts226, sts166, sts231, sts204, sts145, and sts236 are involved in arginine synthesis. sRNAs sts033, sts341, sts492, sts140, sts230, sts172, and sts377 are involved in the ADI pathway. The present study provided valuable information for the functional study of sRNAs in S. thermophilus and indicated a future research direction for sRNA in S. thermophilus. Overall, our results provided new insights for understanding the complex regulatory network of sRNAs in S. thermophilus.
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Affiliation(s)
- Gefei Liu
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
| | - Haode Chang
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
| | - Yali Qiao
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
| | - Kai Huang
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
| | - Ao Zhang
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
| | - Yu Zhao
- Spice and Beverage Research Institute, Chinese Academy of Tropical Agricultural Sciences, Wanning, 571533, Hainan, China
- Yu Zhao,
| | - Zhen Feng
- Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University, 600 Chanjiang Road,150030, Harbin, Heilongjiang, China
- College of Food and Biological Engineering, Qiqihar University, 42 Wenhua Road, 160006, Qiqihar, China
- *Correspondence: Zhen Feng,
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Engineering of the Small Noncoding RNA (sRNA) DsrA Together with the sRNA Chaperone Hfq Enhances the Acid Tolerance of Escherichia coli. Appl Environ Microbiol 2021; 87:AEM.02923-20. [PMID: 33674434 DOI: 10.1128/aem.02923-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 02/21/2021] [Indexed: 11/20/2022] Open
Abstract
Acid tolerance of microorganisms is a desirable phenotype for many industrial fermentation applications. In Escherichia coli, the stress response sigma factor RpoS is a promising target for engineering acid-tolerant phenotypes. However, the simple overexpression of RpoS alone is insufficient to confer these phenotypes. In this study, we show that the simultaneous overexpression of the noncoding small RNA (sRNA) DsrA and the sRNA chaperone Hfq, which act as RpoS activators, significantly increased acid tolerance in terms of cell growth under modest acidic pH, as well as cell survival upon extreme acid shock. Directed evolution of the DsrA-Hfq module further improved the acid tolerance, with the best mutants showing a 51 to 72% increase in growth performance at pH 4.5 compared with the starting strain, MG1655. Further analyses found that the improved acid tolerance of these DsrA-Hfq strains coincided with activation of genes associated with proton-consuming acid resistance system 2 (AR2), protein chaperone HdeB, and reactive oxygen species (ROS) removal in the exponential phase. This study illustrated that the fine-tuning of sRNAs and their chaperones can be a novel strategy for improving the acid tolerance of E. coli IMPORTANCE Many of the traditional studies on bacterial acid tolerance generally focused on improving cell survival under extreme-pH conditions, but cell growth under less harsh acidic conditions is more relevant to industrial applications. Under normal conditions, the general stress response sigma factor RpoS is maintained at low levels in the growth phase through a number of mechanisms. This study showed that RpoS can be activated prior to the stationary phase via engineering its activators, the sRNA DsrA and the sRNA chaperone Hfq, resulting in significantly improved cell growth at modest acidic pH. This work suggests that the sigma factors and likely other transcription factors can be retuned or retimed by manipulating the respective regulatory sRNAs along with the sufficient supply of the respective sRNA chaperones (i.e., Hfq). This provides a novel avenue for strain engineering of microbes.
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Zhang W, Chen X, Sun W, Nie T, Quanquin N, Sun Y. Escherichia Coli Increases its ATP Concentration in Weakly Acidic Environments Principally through the Glycolytic Pathway. Genes (Basel) 2020; 11:genes11090991. [PMID: 32854287 PMCID: PMC7563387 DOI: 10.3390/genes11090991] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/22/2020] [Accepted: 08/24/2020] [Indexed: 12/23/2022] Open
Abstract
Acid resistance is an intrinsic characteristic of intestinal bacteria in order to survive passage through the stomach. Adenosine triphosphate (ATP), the ubiquitous chemical used to power metabolic reactions, activate signaling cascades, and form precursors of nucleic acids, was also found to be associated with the survival of Escherichia coli (E. coli) in acidic environments. The metabolic pathway responsible for elevating the level of ATP inside these bacteria during acid adaptation has been unclear. E. coli uses several mechanisms of ATP production, including oxidative phosphorylation, glycolysis and the oxidation of organic compounds. To uncover which is primarily used during adaptation to acidic conditions, we broadly analyzed the levels of gene transcription of multiple E. coli metabolic pathway components. Our findings confirmed that the primary producers of ATP in E. coli undergoing mild acidic stress are the glycolytic enzymes Glk, PykF and Pgk, which are also essential for survival under markedly acidic conditions. By contrast, the transcription of genes related to oxidative phosphorylation was downregulated, despite it being the major producer of ATP in neutral pH environments.
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Affiliation(s)
- Wenbin Zhang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou 510640, China;
- Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; (W.S.); (T.N.)
| | - Xin Chen
- Guangdong Key Laboratory of IoT Information Technology, School of Automation, Guangdong University of Technology, Guangzhou 510006, China;
| | - Wei Sun
- Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; (W.S.); (T.N.)
| | - Tao Nie
- Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; (W.S.); (T.N.)
| | - Natalie Quanquin
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA;
| | - Yirong Sun
- Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; (W.S.); (T.N.)
- Correspondence:
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4
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Han Q, Eiteman MA. Acetate formation during recombinant protein production in Escherichia coli K-12 with an elevated NAD(H) pool. Eng Life Sci 2019; 19:770-780. [PMID: 32624970 DOI: 10.1002/elsc.201900045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 08/15/2019] [Accepted: 08/21/2019] [Indexed: 12/14/2022] Open
Abstract
Acetate formation is a disadvantage in the use of Escherichia coli for recombinant protein production, and many studies have focused on optimizing fermentation processes or altering metabolism to eliminate acetate accumulation. In this study, E. coli MEC697 (MG1655 nadR nudC mazG) maintained a larger pool of NAD(H) compared to the wild-type control, and also accumulated lower concentrations of acetate when grown in batch culture on glucose. In steady-state cultures, the elevated total NAD(H) found in MEC697 delayed the threshold dilution rate for acetate formation to a growth rate of 0.27 h-1. Batch and fed-batch processes using MEC697 were examined for the production of β-galactosidase as a model recombinant protein. Fed-batch culture of MEC697/pTrc99A-lacZ compared to MG1655/pTrc99A-lacZ at a growth rate of 0.22 h-1 showed only a modest increase of protein formation. However, 1 L batch growth of MEC697/pTrc99A-lacZ resulted in 50% lower acetate formation compared to MG1655/pTrc99A-lacZ and a two-fold increase in recombinant protein production.
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Affiliation(s)
- Qi Han
- School of Chemical Materials and Biomedical Engineering University of Georgia Athens GA USA
| | - Mark A Eiteman
- School of Chemical Materials and Biomedical Engineering University of Georgia Athens GA USA
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5
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Lozano Terol G, Gallego-Jara J, Sola Martínez RA, Cánovas Díaz M, de Diego Puente T. Engineering protein production by rationally choosing a carbon and nitrogen source using E. coli BL21 acetate metabolism knockout strains. Microb Cell Fact 2019; 18:151. [PMID: 31484572 PMCID: PMC6724240 DOI: 10.1186/s12934-019-1202-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/29/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Escherichia coli (E. coli) is a bacteria that is widely employed in many industries for the production of high interest bio-products such as recombinant proteins. Nevertheless, the use of E. coli for recombinant protein production may entail some disadvantages such as acetate overflow. Acetate is accumulated under some culture conditions, involves a decrease in biomass and recombinant protein production, and its metabolism is related to protein lysine acetylation. Thereby, the carbon and nitrogen sources employed are relevant factors in cell host metabolism, and the study of the central metabolism of E. coli and its regulation is essential for optimizing the production of biomass and recombinant proteins. In this study, our aim was to find the most favourable conditions for carrying out recombinant protein production in E. coli BL21 using two different approaches, namely, manipulation of the culture media composition and the deletion of genes involved in acetate metabolism and Nε-lysine acetylation. RESULTS We evaluated protein overexpression in E. coli BL21 wt and five mutant strains involved in acetate metabolism (Δacs, ΔackA and Δpta) and lysine acetylation (ΔpatZ and ΔcobB) grown in minimal medium M9 (inorganic ammonium nitrogen source) and in complex TB7 medium (peptide-based nitrogen source) supplemented with glucose (PTS carbon source) or glycerol (non-PTS carbon source). We observed a dependence of recombinant protein production on acetate metabolism and the carbon and nitrogen source employed. The use of complex medium supplemented with glycerol as a carbon source entails an increase in protein production and an efficient use of resources, since is a sub-product of biodiesel synthesis. Furthermore, the deletion of the ackA gene results in a fivefold increase in protein production with respect to the wt strain and a reduction in acetate accumulation. CONCLUSION The results showed that the use of diverse carbon and nitrogen sources and acetate metabolism knockout strains can redirect E. coli carbon fluxes to different pathways and affect the final yield of the recombinant protein bioprocess. Thereby, we obtained a fivefold increase in protein production and an efficient use of the resources employing the most suitable strain and culture conditions.
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Affiliation(s)
- Gema Lozano Terol
- Department of Biochemistry and Molecular Biology (B) and Immunology, Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence ''Campus Mare Nostrum'', P.O. Box 4021, 30100, Murcia, Spain
| | - Julia Gallego-Jara
- Department of Biochemistry and Molecular Biology (B) and Immunology, Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence ''Campus Mare Nostrum'', P.O. Box 4021, 30100, Murcia, Spain.
| | - Rosa Alba Sola Martínez
- Department of Biochemistry and Molecular Biology (B) and Immunology, Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence ''Campus Mare Nostrum'', P.O. Box 4021, 30100, Murcia, Spain
| | - Manuel Cánovas Díaz
- Department of Biochemistry and Molecular Biology (B) and Immunology, Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence ''Campus Mare Nostrum'', P.O. Box 4021, 30100, Murcia, Spain
| | - Teresa de Diego Puente
- Department of Biochemistry and Molecular Biology (B) and Immunology, Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence ''Campus Mare Nostrum'', P.O. Box 4021, 30100, Murcia, Spain.
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6
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Zhu Z, Yang P, Wu Z, Zhang J, Du G. Systemic understanding of Lactococcus lactis response to acid stress using transcriptomics approaches. J Ind Microbiol Biotechnol 2019; 46:1621-1629. [PMID: 31414323 DOI: 10.1007/s10295-019-02226-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 08/07/2019] [Indexed: 11/25/2022]
Abstract
During fermentation, acid stress caused by the accumulation of acidic metabolites seriously affects the metabolic activity and production capacity of microbial cells. To elucidate the acid stress-tolerance mechanisms of microbial cells, we performed genome mutagenesis combined with high-throughput technologies to screen acid stress-tolerant strains. Mutant strain Lactococcus lactis WH101 showed a 16,000-fold higher survival rate than that of the parent strain after 5 h of acid shock at pH 4.0 and maintained higher ATP, NH4+, and intracellular pH (pHi) levels during acid stress. Additionally, comparative transcriptomics analysis revealed enhanced regulation of carbohydrate metabolism and sugar transport to provide additional energy, amino acid metabolism and transport to maintain pHi homeostasis and ATP generation, and fatty acid metabolism to enhance cellular acid tolerance. Moreover, overexpression of identified components resulted in 12.6- and 12.9-fold higher survival rates after acid shock for 3 h at pH 4.0 in L. lactis (ArcB) and L. lactis (MalQ) compared to the control strain, respectively. These findings provide valuable insight into the acid stress-response mechanisms of L. lactis and promote the further development of robust industrial strains.
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Affiliation(s)
- Zhengming Zhu
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
| | - Peishan Yang
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
| | - Zhimeng Wu
- The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
| | - Juan Zhang
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China. .,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.
| | - Guocheng Du
- The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
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7
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Julius C, Yuzenkova Y. Noncanonical RNA-capping: Discovery, mechanism, and physiological role debate. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1512. [PMID: 30353673 DOI: 10.1002/wrna.1512] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 09/11/2018] [Accepted: 09/27/2018] [Indexed: 11/12/2022]
Abstract
Recently a new type of 5'-RNA cap was discovered. In contrast to the specialized eukaryotic m7 G cap, the novel caps are abundant cellular cofactors like NAD+ . RNAs capped with cofactors are found in prokaryotes and eukaryotes. Unlike m7 G cap, installed by specialized enzymes, cofactors are attached by main enzyme of transcription, RNA polymerase (RNAP). Cofactors act as noncanonical initiating substrates, provided cofactor's nucleoside base-pairs with template DNA at the transcription start site. Adenosine-containing NAD(H), flavin adenine dinucleotide (FAD), and CoA modify transcripts on promoters starting with +1A. Similarly, uridine-containing cell wall precursors, for example, uridine diphosphate-N-acetylglucosamine were shown to cap RNA in vitro on +1U promoters. Noncanonical capping is a universal feature of evolutionary unrelated RNAPs-multisubunit bacterial and eukaryotic RNAPs, and single-subunit mitochondrial RNAP. Cellular concentrations of cofactors, for example, NAD(H) are significantly higher than their Km in transcription. Yet, only a small proportion of a given cellular RNA is noncanonically capped (if at all). This proportion is a net balance between capping, seemingly stochastic, and decapping, possibly determined by RNA folding, protein binding and transcription rate. NUDIX hydrolases in bacteria and eukaryotes, and DXO family proteins eukaryotes act as decapping enzymes for noncanonical caps. The physiological role of noncanonical RNA capping is only starting to emerge. It was demonstrated to affect RNA stability in vivo in bacteria and eukaryotes and to stimulate RNAP promoter escape in vitro in Escherichia coli. NAD+ /NADH capping ratio may connect transcription to cellular redox state. Potentially, noncanonical capping affects mRNA translation, RNA-protein binding and RNA localization. This article is categorized under: RNA Processing > Capping and 5' End Modifications RNA Export and Localization > RNA Localization RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry.
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Affiliation(s)
- Christina Julius
- Centre for Bacterial Cell Biology, Newcastle University, Newcastle upon Tyne, UK
| | - Yulia Yuzenkova
- Centre for Bacterial Cell Biology, Newcastle University, Newcastle upon Tyne, UK
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Zhu Z, Ji X, Wu Z, Zhang J, Du G. Improved acid-stress tolerance of Lactococcus lactis NZ9000 and Escherichia coli BL21 by overexpression of the anti-acid component recT. J Ind Microbiol Biotechnol 2018; 45:1091-1101. [PMID: 30232653 DOI: 10.1007/s10295-018-2075-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/22/2018] [Indexed: 12/01/2022]
Abstract
Acid accumulation caused by carbon metabolism severely affects the fermentation performance of microbial cells. Here, different sources of the recT gene involved in homologous recombination were functionally overexpressed in Lactococcus lactis NZ9000 and Escherichia coli BL21, and their acid-stress tolerances were investigated. Our results showed that L. lactis NZ9000 (ERecT and LRecT) strains showed 1.4- and 10.4-fold higher survival rates against lactic acid (pH 4.0), respectively, and that E. coli BL21 (ERecT) showed 16.7- and 9.4-fold higher survival rates than the control strain against lactic acid (pH 3.8) for 40 and 60 min, respectively. Additionally, we found that recT overexpression in L. lactis NZ9000 improved their growth under acid-stress conditions, as well as increased salt- and ethanol-stress tolerance and intracellular ATP concentrations in L. lactis NZ9000. These findings demonstrated the efficacy of recT overexpression for enhancing acid-stress tolerance and provided a promising strategy for insertion of anti-acid components in different hosts.
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Affiliation(s)
- Zhengming Zhu
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
| | - Xiaomei Ji
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
| | - Zhimeng Wu
- The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China. .,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.
| | - Juan Zhang
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China. .,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.
| | - Guocheng Du
- The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.,School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China
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9
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Gao X, Yang X, Li J, Zhang Y, Chen P, Lin Z. Engineered global regulator H-NS improves the acid tolerance of E. coli. Microb Cell Fact 2018; 17:118. [PMID: 30053876 PMCID: PMC6064147 DOI: 10.1186/s12934-018-0966-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 07/19/2018] [Indexed: 11/25/2022] Open
Abstract
Background Acid stress is often encountered during industrial fermentation as a result of the accumulation of acidic metabolites. Acid stress increases the intracellular acidity and can cause DNA damage and denaturation of essential enzymes, thus leading to a decrease of growth and fermentation yields. Although acid stress can be relieved by addition of a base to the medium, fermentations with acid-tolerant strains are generally considered much more efficient and cost-effective. Results In this study, the global regulator H-NS was found to have significant influence on the acid tolerance of E. coli. The final OD600 of strains overexpressing H-NS increased by 24% compared to control, when cultured for 24 h at pH 4.5 using HCl as an acid agent. To further improve the acid tolerance, a library of H-NS was constructed by error-prone PCR and subjected to selection. Five mutants that conferred a significant growth advantage compared to the control strain were obtained. The final OD600 of strains harboring the five H-NS mutants was enhanced by 26–53%, and their survival rate was increased by 10- to 100-fold at pH 2.5. Further investigation showed that the improved acid tolerance of H-NS mutants coincides with the activation of multiple acid resistance mechanisms, in particular the glutamate- and glutamine-dependent acid resistance system (AR2). The improved acid tolerance of H-NS mutants was also demonstrated in media acidified by acetic acid and succinic acid, which are common acidic fermentation by-products or products. Conclusions The results obtained in this work demonstrate that the engineering of H-NS can enhance the acid tolerance of E. coli. More in general, this study shows the potential of the engineering of global regulators acting as repressors, such as H-NS, as a promising method to obtain phenotypes of interest. This approach could expand the spectrum of application of global transcription machinery engineering. Electronic supplementary material The online version of this article (10.1186/s12934-018-0966-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xianxing Gao
- Department of Chemical Engineering, Tsinghua University, One Tsinghua Garden Road, Beijing, 100084, China
| | - Xiaofeng Yang
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, Guangdong, China
| | - Jiahui Li
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, Guangdong, China
| | - Yan Zhang
- Department of Chemical Engineering, Tsinghua University, One Tsinghua Garden Road, Beijing, 100084, China.,Shenzhen Agricultural Genomics Institute, China Academy of Agricultural Sciences, 7 Pengfei Road, Dapeng District, Shenzhen, 518120, Guangdong, China
| | - Ping Chen
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, Guangdong, China.
| | - Zhanglin Lin
- Department of Chemical Engineering, Tsinghua University, One Tsinghua Garden Road, Beijing, 100084, China. .,School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, Guangdong, China.
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10
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Negrete A, Shiloach J. Improving E. coli growth performance by manipulating small RNA expression. Microb Cell Fact 2017; 16:198. [PMID: 29137641 PMCID: PMC5686845 DOI: 10.1186/s12934-017-0810-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 11/02/2017] [Indexed: 12/17/2022] Open
Abstract
Efficient growth of E. coli, especially for production of recombinant proteins, has been a challenge for the biotechnological industry since the early 1970s. By employing multiple approaches, such as different media composition, various growth strategies and specific genetic manipulations, it is now possible to grow bacteria to concentrations exceeding 100 g/L and to achieve high concentrations of recombinant proteins. Although the growth conditions are carefully monitored and maintained, it is likely that during the growth process cells are exposed to periodic stress conditions, created by fluctuations in pH, dissolved oxygen, temperature, glucose, and salt concentration. These stress circumstances which can occur especially in large volume bioreactors, may affect the growth and production process. In the last several years, it has been recognized that small non-coding RNAs can act as regulators of bacterial gene expression. These molecules are found to be specifically involved in E. coli response to different environmental stress conditions; but so far, have not been used for improving production strains. The review provides summary of small RNAs identified on petri dish or in shake flask culture that can potentially affect growth characteristics of E. coli grown in bioreactor. Among them MicC and MicF that are involved in response to temperature changes, RyhB that responds to iron concentration, Gady which is associated with lower pH, Sgrs that is coupled with glucose transport and OxyS that responds to oxygen concentration. The manipulation of some of these small RNAs for improving growth of E. coli in Bioreactor is described in the last part of the review. Overexpression of SgrS was associated with improved growth and reduced acetate expression, over expression of GadY improved cell growth at acidic conditions and over expression of OxyS reduced the effect of oxidative stress. One of the possible advantages of manipulating sRNAs for improving cell growth is that the modifications occur at a post-translational level. Therefore, the use of sRNAs may exert minimal effect on the overall bacterial metabolism. The elucidation of the physiological role of newly discovered sRNAs will open new possibilities for creating strains with improved growth and production capabilities.
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Affiliation(s)
- Alejandro Negrete
- Biotechnology Core Laboratory, NIDDK, NIH, Bethesda, MD, 20892, USA.,MilliporeSigma, Carlsbad, CA, 92009, USA
| | - Joseph Shiloach
- Biotechnology Core Laboratory, NIDDK, NIH, Bethesda, MD, 20892, USA.
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11
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Bernal V, Castaño-Cerezo S, Cánovas M. Acetate metabolism regulation in Escherichia coli: carbon overflow, pathogenicity, and beyond. Appl Microbiol Biotechnol 2016; 100:8985-9001. [DOI: 10.1007/s00253-016-7832-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 08/22/2016] [Accepted: 08/24/2016] [Indexed: 12/11/2022]
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Liu M, Zhu ZT, Tao XY, Wang FQ, Wei DZ. RNA-Seq analysis uncovers non-coding small RNA system of Mycobacterium neoaurum in the metabolism of sterols to accumulate steroid intermediates. Microb Cell Fact 2016; 15:64. [PMID: 27112590 PMCID: PMC4845491 DOI: 10.1186/s12934-016-0462-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Accepted: 04/13/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Understanding the metabolic mechanism of sterols to produce valuable steroid intermediates in mycobacterium by a noncoding small RNA (sRNA) view is still limited. In the work, RNA-seq was implemented to investigate the noncoding transcriptome of Mycobacterium neoaurum (Mn) in the transformation process of sterols to valuable steroid intermediates, including 9α-hydroxy-4-androstene-3,17-dione (9OHAD), 1,4-androstadiene-3,17-dione (ADD), and 22-hydroxy-23, 24-bisnorchola-1,4-dien-3-one (1,4-BNA). RESULTS A total of 263 sRNA candidates were predicted from the intergenic regions in Mn. Differential expression of sRNA candidates was explored in the wide type Mn with vs without sterol addition, and the steroid intermediate producing Mn strains vs wide type Mn with sterol addition, respectively. Generally, sRNA candidates were differentially expressed in various strains, but there were still some shared candidates with outstandingly upregulated or downregulated expression in these steroid producing strains. Accordingly, four regulatory networks were constructed to reveal the direct and/or indirect interactions between sRNA candidates and their target genes in four groups, including wide type Mn with vs without sterol addition, 9OHAD, ADD, and BNA producing strains vs wide type Mn with sterol addition, respectively. Based on these constructed networks, several highly focused sRNA candidates were discovered to be prevalent in the networks, which showed comprehensive regulatory roles in various cellular processes, including lipid transport and metabolism, amino acid transport and metabolism, signal transduction, cell envelope biosynthesis and ATP synthesis. To explore the functional role of sRNA candidates in Mn cells, we manipulated the overexpression of candidates 131 and 138 in strain Mn-9OHAD, which led to enhanced production of 9OHAD from 1.5- to 2.3-fold during 6 d' fermentation and a slight effect on growth rate. CONCLUSIONS This study revealed the complex and important regulatory roles of noncoding small RNAs in the metabolism of sterols to produce steroid intermediates in Mn, further analysis of which will promote the better understanding about the molecular metabolism of these sRNA candidates and open a broad range of opportunities in the field.
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Affiliation(s)
- Min Liu
- State key Lab of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology, Shanghai, 200237 China
| | - Zhan-Tao Zhu
- State key Lab of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology, Shanghai, 200237 China
| | - Xin-Yi Tao
- State key Lab of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology, Shanghai, 200237 China
| | - Feng-Qing Wang
- State key Lab of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology, Shanghai, 200237 China
| | - Dong-Zhi Wei
- State key Lab of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology, Shanghai, 200237 China
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