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Patakova P, Branska B, Vasylkivska M, Jureckova K, Musilova J, Provaznik I, Sedlar K. Transcriptomic studies of solventogenic clostridia, Clostridium acetobutylicum and Clostridium beijerinckii. Biotechnol Adv 2021; 58:107889. [PMID: 34929313 DOI: 10.1016/j.biotechadv.2021.107889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/10/2021] [Accepted: 12/14/2021] [Indexed: 12/13/2022]
Abstract
Solventogenic clostridia are not a strictly defined group within the genus Clostridium but its representatives share some common features, i.e. they are anaerobic, non-pathogenic, non-toxinogenic and endospore forming bacteria. Their main metabolite is typically 1-butanol but depending on species and culture conditions, they can form other metabolites such as acetone, isopropanol, ethanol, butyric, lactic and acetic acids, and hydrogen. Although these organisms were previously used for the industrial production of solvents, they later fell into disuse, being replaced by more efficient chemical production. A return to a more biological production of solvents therefore requires a thorough understanding of clostridial metabolism. Transcriptome analysis, which reflects the involvement of individual genes in all cellular processes within a population, at any given (sampling) moment, is a valuable tool for gaining a deeper insight into clostridial life. In this review, we describe techniques to study transcription, summarize the evolution of these techniques and compare methods for data processing and visualization of solventogenic clostridia, particularly the species Clostridium acetobutylicum and Clostridium beijerinckii. Individual approaches for evaluating transcriptomic data are compared and their contributions to advancements in the field are assessed. Moreover, utilization of transcriptomic data for reconstruction of computational clostridial metabolic models is considered and particular models are described. Transcriptional changes in glucose transport, central carbon metabolism, the sporulation cycle, butanol and butyrate stress responses, the influence of lignocellulose-derived inhibitors on growth and solvent production, and other respective topics, are addressed and common trends are highlighted.
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Affiliation(s)
- Petra Patakova
- University of Chemistry and Technology Prague, Technicka 5, 16628 Prague 6, Czech Republic.
| | - Barbora Branska
- University of Chemistry and Technology Prague, Technicka 5, 16628 Prague 6, Czech Republic
| | - Maryna Vasylkivska
- University of Chemistry and Technology Prague, Technicka 5, 16628 Prague 6, Czech Republic
| | | | - Jana Musilova
- Brno University of Technology, Technicka 10, 61600 Brno, Czech Republic
| | - Ivo Provaznik
- Brno University of Technology, Technicka 10, 61600 Brno, Czech Republic
| | - Karel Sedlar
- Brno University of Technology, Technicka 10, 61600 Brno, Czech Republic
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Diallo M, Kengen SWM, López-Contreras AM. Sporulation in solventogenic and acetogenic clostridia. Appl Microbiol Biotechnol 2021; 105:3533-3557. [PMID: 33900426 PMCID: PMC8102284 DOI: 10.1007/s00253-021-11289-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 04/03/2021] [Accepted: 04/07/2021] [Indexed: 02/07/2023]
Abstract
The Clostridium genus harbors compelling organisms for biotechnological production processes; while acetogenic clostridia can fix C1-compounds to produce acetate and ethanol, solventogenic clostridia can utilize a wide range of carbon sources to produce commercially valuable carboxylic acids, alcohols, and ketones by fermentation. Despite their potential, the conversion by these bacteria of carbohydrates or C1 compounds to alcohols is not cost-effective enough to result in economically viable processes. Engineering solventogenic clostridia by impairing sporulation is one of the investigated approaches to improve solvent productivity. Sporulation is a cell differentiation process triggered in bacteria in response to exposure to environmental stressors. The generated spores are metabolically inactive but resistant to harsh conditions (UV, chemicals, heat, oxygen). In Firmicutes, sporulation has been mainly studied in bacilli and pathogenic clostridia, and our knowledge of sporulation in solvent-producing or acetogenic clostridia is limited. Still, sporulation is an integral part of the cellular physiology of clostridia; thus, understanding the regulation of sporulation and its connection to solvent production may give clues to improve the performance of solventogenic clostridia. This review aims to provide an overview of the triggers, characteristics, and regulatory mechanism of sporulation in solventogenic clostridia. Those are further compared to the current knowledge on sporulation in the industrially relevant acetogenic clostridia. Finally, the potential applications of spores for process improvement are discussed.Key Points• The regulatory network governing sporulation initiation varies in solventogenic clostridia.• Media composition and cell density are the main triggers of sporulation.• Spores can be used to improve the fermentation process.
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Affiliation(s)
- Mamou Diallo
- Wageningen Food and Biobased Research, Wageningen, The Netherlands.
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands.
| | - Servé W M Kengen
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
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Su Z, Wang F, Xie Y, Xie H, Mao G, Zhang H, Song A, Zhang Z. Reassessment of the role of CaCO 3 in n-butanol production from pretreated lignocellulosic biomass by Clostridium acetobutylicum. Sci Rep 2020; 10:17956. [PMID: 33087773 PMCID: PMC7578090 DOI: 10.1038/s41598-020-74899-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 10/05/2020] [Indexed: 12/25/2022] Open
Abstract
In this study, the role of CaCO3 in n-butanol production was further investigated using corn straw hydrolysate (CSH) media by Clostridium acetobutylicum CICC 8016. CaCO3 addition stimulated sugars utilization and butanol production. Further study showed that calcium salts addition to CSH media led to the increase in Ca2+ concentration both intracellularly and extracellularly. Interestingly, without calcium salts addition, intracellular Ca2+ concentration in the synthetic P2 medium was much higher than that in the CSH medium despite the lower extracellular Ca2+ concentrations in the P2 medium. These results indicated that without additional calcium salts, Ca2+ uptake by C. acetobutylicum CICC 8016 in the CSH medium may be inhibited by non-sugar biomass degradation compounds, such as furans, phenolics and organic acids. Comparative proteomics analysis results showed that most enzymes involved in glycolysis, redox balance and amino acids metabolism were up-regulated with CaCO3 addition. This study provides further insights into the role of CaCO3 in n-butanol production using real biomass hydrolysate.
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Affiliation(s)
- Zengping Su
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China
| | - Fengqin Wang
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China.
| | - Yaohuan Xie
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China
| | - Hui Xie
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China
| | - Guotao Mao
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China
| | - Hongsen Zhang
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China
| | - Andong Song
- Key Laboratory of Agricultural Microbial Enzyme Engineering (Ministry of Agriculture), College of Life Science, Henan Agricultural University, No. 63, Nongye Road, Jinshui District, Zhengzhou, 450002, Henan Province, China.
| | - Zhanying Zhang
- Centre for Agriculture and the Bioeconomy, Institute for Future Environments, Queensland University of Technology, Brisbane, QLD, 4000, Australia.,School of Mechanical, Medical and Process Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD, 4000, Australia
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Vees CA, Neuendorf CS, Pflügl S. Towards continuous industrial bioprocessing with solventogenic and acetogenic clostridia: challenges, progress and perspectives. J Ind Microbiol Biotechnol 2020; 47:753-787. [PMID: 32894379 PMCID: PMC7658081 DOI: 10.1007/s10295-020-02296-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/20/2020] [Indexed: 12/11/2022]
Abstract
The sustainable production of solvents from above ground carbon is highly desired. Several clostridia naturally produce solvents and use a variety of renewable and waste-derived substrates such as lignocellulosic biomass and gas mixtures containing H2/CO2 or CO. To enable economically viable production of solvents and biofuels such as ethanol and butanol, the high productivity of continuous bioprocesses is needed. While the first industrial-scale gas fermentation facility operates continuously, the acetone-butanol-ethanol (ABE) fermentation is traditionally operated in batch mode. This review highlights the benefits of continuous bioprocessing for solvent production and underlines the progress made towards its establishment. Based on metabolic capabilities of solvent producing clostridia, we discuss recent advances in systems-level understanding and genome engineering. On the process side, we focus on innovative fermentation methods and integrated product recovery to overcome the limitations of the classical one-stage chemostat and give an overview of the current industrial bioproduction of solvents.
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Affiliation(s)
- Charlotte Anne Vees
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Christian Simon Neuendorf
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Stefan Pflügl
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
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Degeneration of industrial bacteria caused by genetic instability. World J Microbiol Biotechnol 2020; 36:119. [DOI: 10.1007/s11274-020-02901-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022]
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Vasylkivska M, Jureckova K, Branska B, Sedlar K, Kolek J, Provaznik I, Patakova P. Transcriptional analysis of amino acid, metal ion, vitamin and carbohydrate uptake in butanol-producing Clostridium beijerinckii NRRL B-598. PLoS One 2019; 14:e0224560. [PMID: 31697692 PMCID: PMC6837493 DOI: 10.1371/journal.pone.0224560] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 10/16/2019] [Indexed: 11/19/2022] Open
Abstract
In-depth knowledge of cell metabolism and nutrient uptake mechanisms can lead to the development of a tool for improving acetone-butanol-ethanol (ABE) fermentation performance and help to overcome bottlenecks in the process, such as the high cost of substrates and low production rates. Over 300 genes potentially encoding transport of amino acids, metal ions, vitamins and carbohydrates were identified in the genome of the butanol-producing strain Clostridium beijerinckii NRRL B-598, based on similarity searches in protein function databases. Transcriptomic data of the genes were obtained during ABE fermentation by RNA-Seq experiments and covered acidogenesis, solventogenesis and sporulation. The physiological roles of the selected 81 actively expressed transport genes were established on the basis of their expression profiles at particular stages of ABE fermentation. This article describes how genes encoding the uptake of glucose, iron, riboflavin, glutamine, methionine and other nutrients take part in growth, production and stress responses of C. beijerinckii NRRL B-598. These data increase our knowledge of transport mechanisms in solventogenic Clostridium and may be used in the selection of individual genes for further research.
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Affiliation(s)
- Maryna Vasylkivska
- Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic
- * E-mail:
| | - Katerina Jureckova
- Department of Biomedical Engineering, Brno University of Technology, Brno, Czech Republic
| | - Barbora Branska
- Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic
| | - Karel Sedlar
- Department of Biomedical Engineering, Brno University of Technology, Brno, Czech Republic
| | - Jan Kolek
- Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic
| | - Ivo Provaznik
- Department of Biomedical Engineering, Brno University of Technology, Brno, Czech Republic
| | - Petra Patakova
- Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic
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Acidogenesis, solventogenesis, metabolic stress response and life cycle changes in Clostridium beijerinckii NRRL B-598 at the transcriptomic level. Sci Rep 2019; 9:1371. [PMID: 30718562 PMCID: PMC6362236 DOI: 10.1038/s41598-018-37679-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 12/13/2018] [Indexed: 01/16/2023] Open
Abstract
Clostridium beijerinckii NRRL B-598 is a sporulating, butanol and hydrogen producing strain that utilizes carbohydrates by the acetone-butanol-ethanol (ABE) fermentative pathway. The pathway consists of two metabolic phases, acidogenesis and solventogenesis, from which the latter one can be coupled with sporulation. Thorough transcriptomic profiling during a complete life cycle and both metabolic phases completed with flow cytometry, microscopy and a metabolites analysis helped to find out key genes involved in particular cellular events. The description of genes/operons that are closely involved in metabolism or the cell cycle is a necessary condition for metabolic engineering of the strain and will be valuable for all C. beijerinckii strains and other Clostridial species. The study focused on glucose transport and catabolism, hydrogen formation, metabolic stress response, binary fission, motility/chemotaxis and sporulation, which resulted in the composition of the unique image reflecting clostridial population changes. Surprisingly, the main change in expression of individual genes was coupled with the sporulation start and not with the transition from acidogenic to solventogenic metabolism. As expected, solvents formation started at pH decrease and the accumulation of butyric and acetic acids in the cultivation medium.
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Ahlawat S, Kaushal M, Palabhanvi B, Muthuraj M, Goswami G, Das D. Nutrient modulation based process engineering strategy for improved butanol production from Clostridium acetobutylicum. Biotechnol Prog 2018; 35:e2771. [PMID: 30592566 DOI: 10.1002/btpr.2771] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 12/22/2018] [Indexed: 01/08/2023]
Abstract
The present study demonstrates a process engineering strategy to achieve high butanol titer and productivity from wild type Clostridium acetobutylicum MTCC 11274. In the first step, two different media were optimized with the objectives of maximizing the biomass and butanol productivity, respectively. In the next step, attributes of these two media compositions were integrated to design a two-stage fed-batch process which resulted in maximal butanol productivity of 0.55 g L-1 h-1 with titer of 13.1 g L-1 . Further, two-stage fed-batch process along with combinatorial use of magnesium limitation and calcium supplementation resulted in the highest butanol titer and productivity of 16.5 g L-1 and 0.59 g L-1 h-1 , respectively. Finally, integration of the process with gas stripping and modulation of feeding duration resulted in a cumulative butanol titer of 54.3 g L-1 and productivity of 0.58 g L-1 h-1 . The strategy opens up possibility of developing a viable butanol bioprocess. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2771, 2019.
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Affiliation(s)
- Saumya Ahlawat
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
| | - Mehak Kaushal
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
| | - Basavaraj Palabhanvi
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
| | - Muthusivaramapandian Muthuraj
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
| | - Gargi Goswami
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
| | - Debasish Das
- Dept. of Biosciences & Bioengineering, Indian Inst. of Technology, Guwahati, Assam, 781039, India.,DBT-PAN IIT Centre for Bioenergy, Indian Inst. of Technology, Guwahati, Assam, 781039, India
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Yang Y, Nie X, Jiang Y, Yang C, Gu Y, Jiang W. Metabolic regulation in solventogenic clostridia: regulators, mechanisms and engineering. Biotechnol Adv 2018; 36:905-914. [DOI: 10.1016/j.biotechadv.2018.02.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/05/2018] [Accepted: 02/20/2018] [Indexed: 12/31/2022]
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Lu C, Yu L, Varghese S, Yu M, Yang ST. Enhanced robustness in acetone-butanol-ethanol fermentation with engineered Clostridium beijerinckii overexpressing adhE2 and ctfAB. BIORESOURCE TECHNOLOGY 2017; 243:1000-1008. [PMID: 28747008 DOI: 10.1016/j.biortech.2017.07.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/05/2017] [Accepted: 07/06/2017] [Indexed: 06/07/2023]
Abstract
Clostridium beijerinckii CC101 was engineered to overexpress aldehyde/alcohol dehydrogenase (adhE2) and CoA-transferase (ctfAB). Solvent production and acid assimilation were compared between the parental and engineered strains expressing only adhE2 (CC101-SV4) and expressing adhE2, ald and ctfAB (CC101-SV6). CC101-SV4 showed an early butanol production from glucose but stopped pre-maturely at a low butanol concentration of ∼6g/L. Compared to CC101, CC101-SV6 produced more butanol (∼12g/L) from glucose and was able to re-assimilate more acids, which prevented "acid crash" and increased butanol production, under all conditions studied. CC101-SV6 also showed better ability in using glucose and xylose present in sugarcane bagasse hydrolysate, and produced 9.4g/L solvents (acetone, butanol and ethanol) compared to only 2.6g/L by CC101, confirming its robustness and better tolerance to hydrolysate inhibitors. The engineered strain of C. beijerinckii overexpressing adhE2 and ctfAB should have good potential for producing butanol from lignocellulosic biomass hydrolysates.
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Affiliation(s)
- Congcong Lu
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Ave., Columbus, OH 43210, United States
| | - Le Yu
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Ave., Columbus, OH 43210, United States
| | - Saju Varghese
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Ave., Columbus, OH 43210, United States
| | - Mingrui Yu
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Ave., Columbus, OH 43210, United States
| | - Shang-Tian Yang
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Ave., Columbus, OH 43210, United States.
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Zhang Y, Jiao S, Lv J, Du R, Yan X, Wan C, Zhang R, Han B. Sigma Factor Regulated Cellular Response in a Non-solvent Producing Clostridium beijerinckii Degenerated Strain: A Comparative Transcriptome Analysis. Front Microbiol 2017; 8:23. [PMID: 28194137 PMCID: PMC5276810 DOI: 10.3389/fmicb.2017.00023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 01/04/2017] [Indexed: 01/11/2023] Open
Abstract
Clostridium beijerinckii DG-8052, derived from NCIMB 8052, cannot produce solvent or form spores, a phenomenon known as degeneration. To explore the mechanisms of degeneration at the gene level, transcriptomic profiles of the wild-type 8052 and DG-8052 strains were compared. Expression of 5168 genes comprising 98.6% of the genome was assessed. Interestingly, 548 and 702 genes were significantly up-regulated in the acidogenesis and solventogenesis phases of DG-8052, respectively, and mainly responsible for the phosphotransferase system, sugar metabolic pathways, and chemotaxis; meanwhile, 699 and 797 genes were significantly down-regulated, respectively, and mainly responsible for sporulation, oxidoreduction, and solventogenesis. The functions of some altered genes, including 286 and 333 at the acidogenesis and solventogenesis phases, respectively, remain unknown. Dysregulation of the fermentation machinery was accompanied by lower transcription levels of glycolysis rate-limiting enzymes (pfk and pyk), and higher transcription of cell chemotaxis genes (cheA, cheB, cheR, cheW, and cheY), controlled mainly by σ54 at acidogenesis. Meanwhile, abnormal spore formation was associated with repressed spo0A, sigE, sigF, sigG, and sigK which are positively regulated by σ70, and correspondingly inhibited expression of CoA-transferase at the solventogenesis phase. These findings indicated that morphological and physiological changes in the degenerated Clostridium strain may be related to altered expression of sigma factors, providing valuable targets for strain development of Clostridium species.
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Affiliation(s)
- Yan Zhang
- School of Medicine, Institute for Genome Sciences, University of Maryland, Baltimore MD, USA
| | - Shengyin Jiao
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
| | - Jia Lv
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
| | - Renjia Du
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
| | - Xiaoni Yan
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
| | - Caixia Wan
- Department of Bioengineering, University of Missouri, Columbia MO, USA
| | - Ruijuan Zhang
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
| | - Bei Han
- School of Public Health, Health Science Center, Xi'an Jiaotong University Xi'an, China
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