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Generation of bright autobioluminescent bacteria by chromosomal integration of the improved lux operon ilux2. Sci Rep 2022; 12:19039. [PMID: 36351939 PMCID: PMC9646698 DOI: 10.1038/s41598-022-22068-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 10/10/2022] [Indexed: 11/10/2022] Open
Abstract
The bacterial bioluminescence system enables the generation of light by living cells without the requirement of an external luciferin. Due to the relatively low light emission, many applications of bioluminescence imaging would benefit from an increase in brightness of this system. In this report, a new approach of mutagenesis and screening of the involved proteins is described that is based on the identification of mutants with improved properties under rate-limiting reaction conditions. Multiple rounds of screening in Escherichia coli resulted in the operon ilux2 that contains 26 new mutations in the fatty acid reductase complex which provides the aldehyde substrate for the bioluminescence reaction. Chromosomal integration of ilux2 yielded an autonomously bioluminescent E. coli strain with sixfold increased brightness compared to the previously described ilux operon. The ilux2 strain produces sufficient signal for the robust detection of individual cells and enables highly sensitive long-term imaging of bacterial propagation without a selection marker.
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Nguyen DH, You SH, Vo ATN, Ngo HTT, Van Nguyen K, Duong MTQ, Choy HE, Song M, Hong Y, Min JJ. Optimized Doxycycline-Inducible Gene Expression System for Genetic Programming of Tumor-Targeting Bacteria. Mol Imaging Biol 2021; 24:82-92. [PMID: 34403085 PMCID: PMC8760206 DOI: 10.1007/s11307-021-01624-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/29/2021] [Accepted: 06/10/2021] [Indexed: 01/21/2023]
Abstract
PURPOSE In the programming of tumor-targeting bacteria, various therapeutic or reporter genes are expressed by different gene-triggering strategies. Previously, we engineered pJL87 plasmid with an inducible bacterial drug delivery system that simultaneously co-expressed two genes for therapy and imaging by a bidirectional tet promoter system only in response to the administration of exogenous doxycycline (Doxy). In this multi-cassette expression approach, tetA promoter (PtetA) was 100-fold higher in expression strength than tetR promoter (PtetR). In the present study, we developed pJH18 plasmid with novel Doxy-inducible gene expression system based on a tet promoter. PROCEDURES In this system, Tet repressor (TetR) expressed by a weak constitutive promoter binds to tetO operator, resulting in the tight repression of gene expressions by PtetA and PtetR, and Doxy releases TetR from tetO to de-repress PtetA and PtetR. RESULTS In Salmonella transformed with pJH18, the expression balance of bidirectional tet promoters in pJH18 was remarkably improved (PtetA:PtetR = 4~6:1) compared with that of pJL87 (PtetA:PtetR = 100:1) in the presence of Doxy. Also, the expression level by novel tet system was much higher in Salmonella transformed with pJH18 than in those with pJL87 (80-fold in rluc8 and 5-fold in clyA). Interestingly, pJH18 of the transformed Salmonella was much more stably maintained than pJL87 in antibiotic-free tumor-bearing mice (about 41-fold), because only pJH18 carries bom sequence with an essential role in preventing the plasmid-free population of programmed Salmonella from undergoing cell division. CONCLUSIONS Overall, doxycycline-induced co-expression of two proteins at similar expression levels, we exploited bioluminescence reporter proteins with preclinical but no clinical utility. Future validation with clinically compatible reporter systems, for example, suitable for radionuclide imaging, is necessary to develop this system further towards potential clinical application.
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Affiliation(s)
- Dinh-Huy Nguyen
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Sung-Hwan You
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - An-Trang Ngoc Vo
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Hien Thi-Thu Ngo
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Khuynh Van Nguyen
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Mai Thi-Quynh Duong
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Hyon E Choy
- Department of Microbiology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Miryoung Song
- Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Yongin, South Korea
| | - Yeongjin Hong
- Department of Microbiology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
| | - Jung-Joon Min
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea.
- Department of Nuclear Medicine, Chonnam National University Medical School, Jeonnam, Gwangju, 61469, Republic of Korea.
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Patwardhan RB, Dhakephalkar PK, Chopade BA, Dhavale DD, Bhonde RR. Purification and Characterization of an Active Principle, Lawsone, Responsible for the Plasmid Curing Activity of Plumbago zeylanica Root Extracts. Front Microbiol 2018; 9:2618. [PMID: 30467495 PMCID: PMC6236066 DOI: 10.3389/fmicb.2018.02618] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 10/12/2018] [Indexed: 12/17/2022] Open
Abstract
Plasmid curing is the process of obviating the plasmid encoded functions such as antibiotic resistance, virulence, degradation of aromatic compounds, etc. in bacteria. Several plasmid curing agents have been reported in literature, however, no plasmid curing agent can eliminate all plasmids from different hosts. Hence, there is always a need for novel plasmid curing agents that can be effectively used for reversal of plasmid encoded functions such as virulence, antibiotic resistance, etc. In the present study, an active principle responsible for the plasmid curing activity was purified from roots of Plumbago zeylanica by bioassay guided fractionation and identified as 2-hydroxy-1,4-naphthoquinone (lawsone), on the basis of spectral and analytical data such as NMR, GCMS, FTIR. Plasmid curing activity of lawsone was observed against reference as well as wild plasmids (pBR322, pRK2013, R136, pUPI281, and pUPI282) residing in a range of hosts. Curing of plasmid was confirmed by agarose gel electrophoresis. MICs of antibiotics against A. baumannii A24 (pUPI281) and E. coli (pRK2013) decreased significantly in presence of lawsone suggesting synergy between lawsone and antibiotics. Lawsone also inhibited transfer of plasmid pRK2013 to E. coli either by transformation or conjugation. Viability assays (MTT) revealed that lawsone was not toxic to mammalian cells. Thus, the present investigation has revealed lawsone as an effective plasmid curing agent capable of suppressing development and spread of antibiotic resistance. Further, lawsone has important application in basic research to identify phenotypes encoded by the plasmids in plasmid curing experiments. To the best of our knowledge this is the first report of plasmid curing activity of lawsone isolated from roots of P. zeylanica.
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Affiliation(s)
| | | | - Balu Ananda Chopade
- Department of Microbiology, Savitribai Phule Pune University, Aurangabad, India
| | - Dilip D Dhavale
- Department of Chemistry, Savitribai Phule Pune University, Pune, India
| | - Ramesh R Bhonde
- School of Regenerative Medicine - Manipal Academy of Higher Education, Bengaluru, India
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