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Fricke PM, Gries ML, Mürköster M, Höninger M, Gätgens J, Bott M, Polen T. The l-rhamnose-dependent regulator RhaS and its target promoters from Escherichia coli expand the genetic toolkit for regulatable gene expression in the acetic acid bacterium Gluconobacter oxydans. Front Microbiol 2022; 13:981767. [PMID: 36060754 PMCID: PMC9429829 DOI: 10.3389/fmicb.2022.981767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 07/13/2022] [Indexed: 11/25/2022] Open
Abstract
For regulatable target gene expression in the acetic acid bacterium (AAB) Gluconobacter oxydans only recently the first plasmids became available. These systems solely enable AraC- and TetR-dependent induction. In this study we showed that the l-rhamnose-dependent regulator RhaS from Escherichia coli and its target promoters PrhaBAD, PrhaT, and PrhaSR could also be used in G. oxydans for regulatable target gene expression. Interestingly, in contrast to the responsiveness in E. coli, in G. oxydans RhaS increased the expression from PrhaBAD in the absence of l-rhamnose and repressed PrhaBAD in the presence of l-rhamnose. Inserting an additional RhaS binding site directly downstream from the −10 region generating promoter variant PrhaBAD(+RhaS-BS) almost doubled the apparent RhaS-dependent promoter strength. Plasmid-based PrhaBAD and PrhaBAD(+RhaS-BS) activity could be reduced up to 90% by RhaS and l-rhamnose, while a genomic copy of PrhaBAD(+RhaS-BS) appeared fully repressed. The RhaS-dependent repression was largely tunable by l-rhamnose concentrations between 0% and only 0.3% (w/v). The RhaS-PrhaBAD and the RhaS-PrhaBAD(+RhaS-BS) systems represent the first heterologous repressible expression systems for G. oxydans. In contrast to PrhaBAD, the E. coli promoter PrhaT was almost inactive in the absence of RhaS. In the presence of RhaS, the PrhaT activity in the absence of l-rhamnose was weak, but could be induced up to 10-fold by addition of l-rhamnose, resulting in a moderate expression level. Therefore, the RhaS-PrhaT system could be suitable for tunable low-level expression of difficult enzymes or membrane proteins in G. oxydans. The insertion of an additional RhaS binding site directly downstream from the E. coli PrhaT −10 region increased the non-induced expression strength and reversed the regulation by RhaS and l-rhamnose from inducible to repressible. The PrhaSR promoter appeared to be positively auto-regulated by RhaS and this activation was increased by l-rhamnose. In summary, the interplay of the l-rhamnose-binding RhaS transcriptional regulator from E. coli with its target promoters PrhaBAD, PrhaT, PrhaSR and variants thereof provide new opportunities for regulatable gene expression in G. oxydans and possibly also for simultaneous l-rhamnose-triggered repression and activation of target genes, which is a highly interesting possibility in metabolic engineering approaches requiring redirection of carbon fluxes.
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da Silva GAR, Oliveira SSDS, Lima SF, do Nascimento RP, Baptista ARDS, Fiaux SB. The industrial versatility of Gluconobacter oxydans: current applications and future perspectives. World J Microbiol Biotechnol 2022; 38:134. [PMID: 35688964 PMCID: PMC9187504 DOI: 10.1007/s11274-022-03310-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 05/13/2022] [Indexed: 11/26/2022]
Abstract
Gluconobacter oxydans is a well-known acetic acid bacterium that has long been applied in the biotechnological industry. Its extraordinary capacity to oxidize a variety of sugars, polyols, and alcohols into acids, aldehydes, and ketones is advantageous for the production of valuable compounds. Relevant G. oxydans industrial applications are in the manufacture of L-ascorbic acid (vitamin C), miglitol, gluconic acid and its derivatives, and dihydroxyacetone. Increasing efforts on improving these processes have been made in the last few years, especially by applying metabolic engineering. Thereby, a series of genes have been targeted to construct powerful recombinant strains to be used in optimized fermentation. Furthermore, low-cost feedstocks, mostly agro-industrial wastes or byproducts, have been investigated, to reduce processing costs and improve the sustainability of G. oxydans bioprocess. Nonetheless, further research is required mainly to make these raw materials feasible at the industrial scale. The current shortage of suitable genetic tools for metabolic engineering modifications in G. oxydans is another challenge to be overcome. This paper aims to give an overview of the most relevant industrial G. oxydans processes and the current strategies developed for their improvement.
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Affiliation(s)
- Gabrielle Alves Ribeiro da Silva
- Graduate Program in Science and Biotechnology, Biology Institute, Fluminense Federal University (UFF), Niterói-RJ, 24020-141, Brazil.
- Microbial Technology Laboratory, Pharmaceutical Technology Department, Faculty of Pharmacy, Fluminense Federal University (UFF), Niterói-RJ, 24241-000, Brazil.
- Ecology of Microbial Process Laboratory, Biochemical Engineering Department, Chemical School, Technology Center, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro-RJ, 21941-909, Brazil.
| | - Simone Santos de Sousa Oliveira
- Graduate Program in Science and Biotechnology, Biology Institute, Fluminense Federal University (UFF), Niterói-RJ, 24020-141, Brazil
- Microbial Technology Laboratory, Pharmaceutical Technology Department, Faculty of Pharmacy, Fluminense Federal University (UFF), Niterói-RJ, 24241-000, Brazil
| | - Sara Fernandes Lima
- Microbial Technology Laboratory, Pharmaceutical Technology Department, Faculty of Pharmacy, Fluminense Federal University (UFF), Niterói-RJ, 24241-000, Brazil
| | - Rodrigo Pires do Nascimento
- Ecology of Microbial Process Laboratory, Biochemical Engineering Department, Chemical School, Technology Center, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro-RJ, 21941-909, Brazil
| | - Andrea Regina de Souza Baptista
- Center for Microorganisms Investigation, Microbiology and Parasitology Department, Biomedical Institute, Fluminense Federal University (UFF), Niterói-RJ, 24020-141, Brazil
| | - Sorele Batista Fiaux
- Microbial Technology Laboratory, Pharmaceutical Technology Department, Faculty of Pharmacy, Fluminense Federal University (UFF), Niterói-RJ, 24241-000, Brazil
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Fricke PM, Link T, Gätgens J, Sonntag C, Otto M, Bott M, Polen T. A tunable L-arabinose-inducible expression plasmid for the acetic acid bacterium Gluconobacter oxydans. Appl Microbiol Biotechnol 2020; 104:9267-9282. [PMID: 32974745 PMCID: PMC7567684 DOI: 10.1007/s00253-020-10905-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 09/04/2020] [Accepted: 09/10/2020] [Indexed: 01/21/2023]
Abstract
Abstract The acetic acid bacterium (AAB) Gluconobacter oxydans incompletely oxidizes a wide variety of carbohydrates and is therefore used industrially for oxidative biotransformations. For G. oxydans, no system was available that allows regulatable plasmid-based expression. We found that the l-arabinose-inducible PBAD promoter and the transcriptional regulator AraC from Escherichia coli MC4100 performed very well in G. oxydans. The respective pBBR1-based plasmids showed very low basal expression of the reporters β-glucuronidase and mNeonGreen, up to 480-fold induction with 1% l-arabinose, and tunability from 0.1 to 1% l-arabinose. In G. oxydans 621H, l-arabinose was oxidized by the membrane-bound glucose dehydrogenase, which is absent in the multi-deletion strain BP.6. Nevertheless, AraC-PBAD performed similar in both strains in the exponential phase, indicating that a gene knockout is not required for application of AraC-PBAD in wild-type G. oxydans strains. However, the oxidation product arabinonic acid strongly contributed to the acidification of the growth medium in 621H cultures during the stationary phase, which resulted in drastically decreased reporter activities in 621H (pH 3.3) but not in BP.6 cultures (pH 4.4). These activities could be strongly increased quickly solely by incubating stationary cells in d-mannitol-free medium adjusted to pH 6, indicating that the reporters were hardly degraded yet rather became inactive. In a pH-controlled bioreactor, these reporter activities remained high in the stationary phase (pH 6). Finally, we created a multiple cloning vector with araC-PBAD based on pBBR1MCS-5. Together, we demonstrated superior functionality and good tunability of an AraC-PBAD system in G. oxydans that could possibly also be used in other AAB. Key points • We found the AraC-PBADsystem from E. coli MC4100 was well tunable in G. oxydans. • In the absence of AraC orl-arabinose, expression from PBADwas extremely low. • This araC-PBADsystem could also be fully functional in other acetic acid bacteria. Electronic supplementary material The online version of this article (10.1007/s00253-020-10905-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Philipp Moritz Fricke
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Tobias Link
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Jochem Gätgens
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Christiane Sonntag
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Maike Otto
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Michael Bott
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Tino Polen
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
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Rohweder B, Lehmann G, Eichner N, Polen T, Rajendran C, Ruperti F, Linde M, Treiber T, Jung O, Dettmer K, Meister G, Bott M, Gronwald W, Sterner R. Library Selection with a Randomized Repertoire of (βα) 8-Barrel Enzymes Results in Unexpected Induction of Gene Expression. Biochemistry 2019; 58:4207-4217. [PMID: 31557000 DOI: 10.1021/acs.biochem.9b00579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The potential of the frequently encountered (βα)8-barrel fold to acquire new functions was tested by an approach combining random mutagenesis and selection in vivo. For this purpose, the genes encoding 52 different phosphate-binding (βα)8-barrel proteins were subjected to error-prone PCR and cloned into an expression plasmid. The resulting mixed repertoire was used to transform different auxotrophic Escherichia coli strains, each lacking an enzyme with a phosphate-containing substrate. After plating of the different transformants on minimal medium, growth was observed only for two strains, lacking either the gene for the serine phosphatase SerB or the phosphoserine aminotransferase SerC. The same mutants of the E. coli genes nanE (encoding a putative N-acetylmannosamine-6-phosphate 2-epimerase) and pdxJ (encoding the pyridoxine 5'-phosphate synthase) were responsible for rescuing both ΔserB and ΔserC. Unexpectedly, the complementing NanE and PdxJ variants did not catalyze the SerB or SerC reactions in vitro. Instead, RT-qPCR, RNAseq, and transcriptome analysis showed that they rescue the deletions by enlisting the help of endogenous E. coli enzymes HisB and HisC through exclusive up-regulation of histidine operon transcription. While the promiscuous SerB activity of HisB is well-established, our data indicate that HisC is promiscuous for the SerC reaction, as well. The successful rescue of ΔserB and ΔserC through point mutations and recruitment of additional amino acids in NanE and PdxJ provides another example for the adaptability of the (βα)8-barrel fold.
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Affiliation(s)
- Bettina Rohweder
- Institute of Biophysics and Physical Biochemistry , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Gerhard Lehmann
- Institute of Biochemistry, Genetics and Microbiology , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Norbert Eichner
- Institute of Biochemistry, Genetics and Microbiology , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Tino Polen
- IBG-1: Biotechnology , Institute of Bio- and Geosciences , Forschungszentrum Jülich GmbH , D-52425 Jülich , Germany
| | - Chitra Rajendran
- Institute of Biophysics and Physical Biochemistry , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Fabian Ruperti
- Institute of Biophysics and Physical Biochemistry , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Mona Linde
- Institute of Biophysics and Physical Biochemistry , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Thomas Treiber
- Institute of Biochemistry, Genetics and Microbiology , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Oona Jung
- Institute of Functional Genomics , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Katja Dettmer
- Institute of Functional Genomics , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Gunter Meister
- Institute of Biochemistry, Genetics and Microbiology , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Michael Bott
- IBG-1: Biotechnology , Institute of Bio- and Geosciences , Forschungszentrum Jülich GmbH , D-52425 Jülich , Germany
| | - Wolfram Gronwald
- Institute of Functional Genomics , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
| | - Reinhard Sterner
- Institute of Biophysics and Physical Biochemistry , University of Regensburg , Universitätsstrasse 31 , D-93053 Regensburg , Germany
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