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Gumulya Y, Boxall NJ, Khaleque HN, Santala V, Carlson RP, Kaksonen AH. In a quest for engineering acidophiles for biomining applications: challenges and opportunities. Genes (Basel) 2018; 9:E116. [PMID: 29466321 PMCID: PMC5852612 DOI: 10.3390/genes9020116] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 02/16/2018] [Accepted: 02/16/2018] [Indexed: 12/27/2022] Open
Abstract
Biomining with acidophilic microorganisms has been used at commercial scale for the extraction of metals from various sulfide ores. With metal demand and energy prices on the rise and the concurrent decline in quality and availability of mineral resources, there is an increasing interest in applying biomining technology, in particular for leaching metals from low grade minerals and wastes. However, bioprocessing is often hampered by the presence of inhibitory compounds that originate from complex ores. Synthetic biology could provide tools to improve the tolerance of biomining microbes to various stress factors that are present in biomining environments, which would ultimately increase bioleaching efficiency. This paper reviews the state-of-the-art tools to genetically modify acidophilic biomining microorganisms and the limitations of these tools. The first part of this review discusses resilience pathways that can be engineered in acidophiles to enhance their robustness and tolerance in harsh environments that prevail in bioleaching. The second part of the paper reviews the efforts that have been carried out towards engineering robust microorganisms and developing metabolic modelling tools. Novel synthetic biology tools have the potential to transform the biomining industry and facilitate the extraction of value from ores and wastes that cannot be processed with existing biomining microorganisms.
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Affiliation(s)
- Yosephine Gumulya
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Floreat WA 6014, Australia.
| | - Naomi J Boxall
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Floreat WA 6014, Australia.
| | - Himel N Khaleque
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Floreat WA 6014, Australia.
| | - Ville Santala
- Laboratory of Chemistry and Bioengineering, Tampere University of Technology (TUT), Tampere, 33101, Finland.
| | - Ross P Carlson
- Department of Chemical and Biological Engineering, Montana State University (MSU), Bozeman, MT 59717, USA.
| | - Anna H Kaksonen
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Floreat WA 6014, Australia.
- School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, WA 6009, Australia.
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Lin L, Ji Y, Tu Q, Huang R, Teng L, Zeng X, Song H, Wang K, Zhou Q, Li Y, Cui Q, He Z, Zhou J, Xu J. Microevolution from shock to adaptation revealed strategies improving ethanol tolerance and production in Thermoanaerobacter. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:103. [PMID: 23875846 PMCID: PMC3751872 DOI: 10.1186/1754-6834-6-103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 07/17/2013] [Indexed: 05/08/2023]
Abstract
INTRODUCTION The molecular links between shock-response and adaptation remain poorly understood, particularly for extremophiles. This has hindered rational engineering of solvent tolerance and correlated traits (e.g., productivity) in extremophiles. To untangle such molecular links, here we established a model that tracked the microevolution from shock to adaptation in thermophilic bacteria. METHOD Temporal dynamics of genomes and transcriptomes was tracked for Thermoanaerobacter sp. X514 which under increasing exogenous ethanol evolved from ethanol-sensitive wild-type (Strain X) to tolerance of 2%- (XI) and eventually 6%-ethanol (XII). Based on the reconstructed transcriptional network underlying stress tolerance, genetic engineering was employed to improve ethanol tolerance and production in Thermoanaerobacter. RESULTS The spontaneous genome mutation rate (μg) of Thermoanaerobacter sp. X514, calculated at 0.045, suggested a higher mutation rate in thermophile than previously thought. Transcriptomic comparison revealed that shock-response and adaptation were distinct in nature, whereas the transcriptomes of XII resembled those of the extendedly shocked X. To respond to ethanol shock, X employed fructose-specific phosphotransferase system (PTS), Arginine Deiminase (ADI) pathway, alcohol dehydrogenase (Adh) and a distinct mechanism of V-type ATPase. As an adaptation to exogenous ethanol, XI mobilized resistance-nodulation-cell division (RND) efflux system and Adh, whereas XII, which produced higher ethanol than XI, employed ECF-type ϭ24, an alcohol catabolism operon and phase-specific heat-shock proteins (Hsps), modulated hexose/pentose-transport operon structure and reinforced membrane rigidity. Exploiting these findings, we further showed that ethanol productivity and tolerance can be improved simultaneously by overexpressing adh or ϭ24 in X. CONCLUSION Our work revealed thermophilic-bacteria specific features of adaptive evolution and demonstrated a rational strategy to engineer co-evolving industrial traits. As improvements of shock-response, stress tolerance and productivity have been crucial aims in industrial applications employing thermophiles, our findings should be valuable not just to the production of ethanol but also to a wide variety of biofuels and biochemicals.
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Affiliation(s)
- Lu Lin
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Yuetong Ji
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Qichao Tu
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA
| | - Ranran Huang
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Lin Teng
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Xiaowei Zeng
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Houhui Song
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Kun Wang
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Qian Zhou
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Yifei Li
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Qiu Cui
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
| | - Zhili He
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA
| | - Jizhong Zhou
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA
| | - Jian Xu
- BioEnergy Genome Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, P. R. China
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Multiple propionyl coenzyme A-supplying pathways for production of the bioplastic poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in Haloferax mediterranei. Appl Environ Microbiol 2013; 79:2922-31. [PMID: 23435886 DOI: 10.1128/aem.03915-12] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Haloferax mediterranei is able to accumulate the bioplastic poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with more than 10 mol% 3-hydroxyvalerate (3HV) from unrelated carbon sources. However, the pathways that produce propionyl coenzyme A (propionyl-CoA), an important precursor of 3HV monomer, have not yet been determined. Bioinformatic analysis of H. mediterranei genome indicated that this strain uses multiple pathways for propionyl-CoA biosynthesis, including the citramalate/2-oxobutyrate pathway, the aspartate/2-oxobutyrate pathway, the methylmalonyl-CoA pathway, and a novel 3-hydroxypropionate pathway. Cofeeding of pathway intermediates and inactivating pathway-specific genes supported that these four pathways were indeed involved in the biosynthesis of 3HV monomer. The novel 3-hydroxypropionate pathway that couples CO2 assimilation with PHBV biosynthesis was further confirmed by analysis of (13)C positional enrichment in 3HV. Notably, (13)C metabolic flux analysis showed that the citramalate/2-oxobutyrate pathway (53.0% flux) and the 3-hydroxypropionate pathway (30.6% flux) were the two main generators of propionyl-CoA from glucose. In addition, genetic perturbation on the transcriptome of the ΔphaEC mutant (deficient in PHBV accumulation) revealed that a considerable number of genes in the four propionyl-CoA synthetic pathways were significantly downregulated. We determined for the first time four propionyl-CoA-supplying pathways for PHBV production in haloarchaea, particularly including a new 3-hydroxypropionate pathway. These results would provide novel strategies for the production of PHBV with controllable 3HV molar fraction.
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