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Kohlmeier MG, Oresnik IJ. The transport of mannitol in Sinorhizobium meliloti is carried out by a broad-substrate polyol transporter SmoEFGK and is affected by the ability to transport and metabolize fructose. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001371. [PMID: 37505890 PMCID: PMC10433430 DOI: 10.1099/mic.0.001371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/14/2023] [Indexed: 07/29/2023]
Abstract
The smo locus (sorbitol mannitol oxidation) is found on the chromosome of S. meliloti's tripartite genome. Mutations at the smo locus reduce or abolish the ability of the bacterium to grow on several carbon sources, including sorbitol, mannitol, galactitol, d-arabitol and maltitol. The contribution of the smo locus to the metabolism of these compounds has not been previously investigated. Genetic complementation of mutant strains revealed that smoS is responsible for growth on sorbitol and galactitol, while mtlK restores growth on mannitol and d-arabitol. Dehydrogenase assays demonstrate that SmoS and MtlK are NAD+-dependent dehydrogenases catalysing the oxidation of their specific substrates. Transport experiments using a radiolabeled substrate indicate that sorbitol, mannitol and d-arabitol are primarily transported into the cell by the ABC transporter encoded by smoEFGK. Additionally, it was found that a mutation in either frcK, which is found in an operon that encodes the fructose ABC transporter, or a mutation in frk, which encodes fructose kinase, leads to the induction of mannitol transport.
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Affiliation(s)
| | - Ivan J. Oresnik
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
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2
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Amarelle V, Roldán DM, Fabiano E, Guazzaroni ME. Synthetic Biology Toolbox for Antarctic Pseudomonas sp. Strains: Toward a Psychrophilic Nonmodel Chassis for Function-Driven Metagenomics. ACS Synth Biol 2023; 12:722-734. [PMID: 36862944 DOI: 10.1021/acssynbio.2c00543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
One major limitation of function-driven metagenomics is the ability of the host to express the metagenomic DNA correctly. Differences in the transcriptional, translational, and post-translational machinery between the organism to which the DNA belongs and the host strain are all factors that influence the success of a functional screening. For this reason, the use of alternative hosts is an appropriate approach to favor the identification of enzymatic activities in function-driven metagenomics. To be implemented, appropriate tools should be designed to build the metagenomic libraries in those hosts. Moreover, discovery of new chassis and characterization of synthetic biology toolbox in nonmodel bacteria is an active field of research to expand the potential of these organisms in processes of industrial interest. Here, we assessed the suitability of two Antarctic psychrotolerant Pseudomonas strains as putative alternative hosts for function-driven metagenomics using pSEVA modular vectors as scaffold. We determined a set of synthetic biology tools suitable for these hosts and, as a proof of concept, we demonstrated their fitness for heterologous protein expression. These hosts represent a step forward for the prospection and identification of psychrophilic enzymes of biotechnological interest.
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Affiliation(s)
- Vanesa Amarelle
- Departamento de Bioquímica y Genómica Microbianas. Instituto de Investigaciones Biológicas Clemente Estable, Av. Italia 3318, Montevideo 11600, Uruguay
| | - Diego M Roldán
- Departamento de Bioquímica y Genómica Microbianas. Instituto de Investigaciones Biológicas Clemente Estable, Av. Italia 3318, Montevideo 11600, Uruguay
| | - Elena Fabiano
- Departamento de Bioquímica y Genómica Microbianas. Instituto de Investigaciones Biológicas Clemente Estable, Av. Italia 3318, Montevideo 11600, Uruguay
| | - María-Eugenia Guazzaroni
- Departamento de Biologia. FFCLRP, University of São Paulo, 14049-901 Ribeirão Preto, São Paulo, Brazil
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3
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Hawkins JP, Ordonez PA, Oresnik IJ. Characterization of Mutations That Affect the Nonoxidative Pentose Phosphate Pathway in Sinorhizobium meliloti. J Bacteriol 2018; 200:e00436-17. [PMID: 29084855 PMCID: PMC5738737 DOI: 10.1128/jb.00436-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 10/21/2017] [Indexed: 12/12/2022] Open
Abstract
Sinorhizobium meliloti is a Gram-negative alphaproteobacterium that can enter into a symbiotic relationship with Medicago sativa and Medicago truncatula Previous work determined that a mutation in the tkt2 gene, which encodes a putative transketolase, could prevent medium acidification associated with a mutant strain unable to metabolize galactose. Since the pentose phosphate pathway in S. meliloti is not well studied, strains carrying mutations in either tkt2 and tal, which encodes a putative transaldolase, were characterized. Carbon metabolism phenotypes revealed that both mutants were impaired in growth on erythritol and ribose. This phenotype was more pronounced for the tkt2 mutant strain, which also displayed auxotrophy for aromatic amino acids. Changes in pentose phosphate pathway metabolite concentrations were also consistent with a mutation in either tkt2 or tal The concentrations of metabolites in central carbon metabolism were also found to shift dramatically in strains carrying a tkt2 mutation. While the concentrations of proteins involved in central carbon metabolism did not change significantly under any conditions, the levels of those associated with iron acquisition increased in the wild-type strain with erythritol induction. These proteins were not detected in either mutant, resulting in less observable rhizobactin production in the tkt2 mutant. While both mutants were impaired in succinoglycan synthesis, only the tkt2 mutant strain was unable to establish symbiosis with alfalfa. These results suggest that tkt2 and tal play central roles in regulating the carbon flow necessary for carbon metabolism and the establishment of symbiosis.IMPORTANCESinorhizobium meliloti is a model organism for the study of plant-microbe interactions and metabolism, especially because it effects nitrogen fixation. The ability to derive the energy necessary for nitrogen fixation is dependent on an organism's ability to metabolize carbon efficiently. The pentose phosphate pathway is central in the interconversion of hexoses and pentoses. This study characterizes the key enzymes of the nonoxidative branch of the pentose phosphate pathway by using defined genetic mutations and shows the effects the mutations have on the metabolite profile and on physiological processes such as the biosynthesis of exopolysaccharide, as well as the ability to regulate iron acquisition.
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Affiliation(s)
- Justin P Hawkins
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Patricia A Ordonez
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Ivan J Oresnik
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
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4
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Kinfu BM, Jahnke M, Janus M, Besirlioglu V, Roggenbuck M, Meurer R, Vojcic L, Borchert M, Schwaneberg U, Chow J, Streit WR. Recombinant RNA Polymerase from Geobacillus
sp. GHH01 as tool for rapid generation of metagenomic RNAs using in vitro technologies. Biotechnol Bioeng 2017; 114:2739-2752. [DOI: 10.1002/bit.26436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 08/09/2017] [Accepted: 08/21/2017] [Indexed: 01/18/2023]
Affiliation(s)
- Birhanu M. Kinfu
- Microbiology and Biotechnology, Biocenter Klein Flottbek; University of Hamburg; Ohnhorststr Hamburg Germany
| | - Maike Jahnke
- Microbiology and Biotechnology, Biocenter Klein Flottbek; University of Hamburg; Ohnhorststr Hamburg Germany
| | - Mareike Janus
- Microbiology and Biotechnology, Biocenter Klein Flottbek; University of Hamburg; Ohnhorststr Hamburg Germany
| | | | | | | | | | | | | | - Jennifer Chow
- Microbiology and Biotechnology, Biocenter Klein Flottbek; University of Hamburg; Ohnhorststr Hamburg Germany
| | - Wolfgang R. Streit
- Microbiology and Biotechnology, Biocenter Klein Flottbek; University of Hamburg; Ohnhorststr Hamburg Germany
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5
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Cheng J, Romantsov T, Engel K, Doxey AC, Rose DR, Neufeld JD, Charles TC. Functional metagenomics reveals novel β-galactosidases not predictable from gene sequences. PLoS One 2017; 12:e0172545. [PMID: 28273103 PMCID: PMC5342196 DOI: 10.1371/journal.pone.0172545] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 02/06/2017] [Indexed: 11/19/2022] Open
Abstract
The techniques of metagenomics have allowed researchers to access the genomic potential of uncultivated microbes, but there remain significant barriers to determination of gene function based on DNA sequence alone. Functional metagenomics, in which DNA is cloned and expressed in surrogate hosts, can overcome these barriers, and make important contributions to the discovery of novel enzymes. In this study, a soil metagenomic library carried in an IncP cosmid was used for functional complementation for β-galactosidase activity in both Sinorhizobium meliloti (α-Proteobacteria) and Escherichia coli (γ-Proteobacteria) backgrounds. One β-galactosidase, encoded by six overlapping clones that were selected in both hosts, was identified as a member of glycoside hydrolase family 2. We could not identify ORFs obviously encoding possible β-galactosidases in 19 other sequenced clones that were only able to complement S. meliloti. Based on low sequence identity to other known glycoside hydrolases, yet not β-galactosidases, three of these ORFs were examined further. Biochemical analysis confirmed that all three encoded β-galactosidase activity. Lac36W_ORF11 and Lac161_ORF7 had conserved domains, but lacked similarities to known glycoside hydrolases. Lac161_ORF10 had neither conserved domains nor similarity to known glycoside hydrolases. Bioinformatic and structural modeling implied that Lac161_ORF10 protein represented a novel enzyme family with a five-bladed propeller glycoside hydrolase domain. By discovering founding members of three novel β-galactosidase families, we have reinforced the value of functional metagenomics for isolating novel genes that could not have been predicted from DNA sequence analysis alone.
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Affiliation(s)
- Jiujun Cheng
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | | | - Katja Engel
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Andrew C. Doxey
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - David R. Rose
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Josh D. Neufeld
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Trevor C. Charles
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
- * E-mail:
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Cheng J, Nordeste R, Trainer MA, Charles TC. Methods for the Isolation of Genes Encoding Novel PHA Metabolism Enzymes from Complex Microbial Communities. Methods Mol Biol 2017; 1539:237-248. [PMID: 27900694 DOI: 10.1007/978-1-4939-6691-2_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Development of different PHAs as alternatives to petrochemically derived plastics can be facilitated by mining metagenomic libraries for diverse PHA cycle genes that might be useful for synthesis of bio-plastics. The specific phenotypes associated with mutations of the PHA synthesis pathway genes in Sinorhizobium meliloti and Pseudomonas putida, allows the use of powerful selection and screening tools to identify complementing novel PHA synthesis genes. Identification of novel genes through their function rather than sequence facilitates the functional proteins that may otherwise have been excluded through sequence-only screening methodology. We present here methods that we have developed for the isolation of clones expressing novel PHA metabolism genes from metagenomic libraries.
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Affiliation(s)
- Jiujun Cheng
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada, N2L 3G1
| | - Ricardo Nordeste
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada, N2L 3G1
| | - Maria A Trainer
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada, N2L 3G1
| | - Trevor C Charles
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada, N2L 3G1.
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Sathiyanarayanan G, Saibaba G, Kiran GS, Yang YH, Selvin J. Marine sponge-associated bacteria as a potential source for polyhydroxyalkanoates. Crit Rev Microbiol 2016; 43:294-312. [DOI: 10.1080/1040841x.2016.1206060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Ganesan Sathiyanarayanan
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Ganesan Saibaba
- Centre for Pheromone Technology, Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, India
| | - George Seghal Kiran
- Department of Food Science and Technology, Pondicherry University, Kalapet, India
| | - Yung-Hun Yang
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
- Microbial Carbohydrate Resource Bank, Konkuk University, Seoul, South Korea
| | - Joseph Selvin
- Department of Microbiology, Pondicherry University, Kalapet, India
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8
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Contemporary molecular tools in microbial ecology and their application to advancing biotechnology. Biotechnol Adv 2015; 33:1755-73. [DOI: 10.1016/j.biotechadv.2015.09.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 09/19/2015] [Accepted: 09/20/2015] [Indexed: 12/30/2022]
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9
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Identification of glycosyl hydrolases from a metagenomic library of microflora in sugarcane bagasse collection site and their cooperative action on cellulose degradation. J Biosci Bioeng 2015; 119:384-91. [DOI: 10.1016/j.jbiosc.2014.09.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 08/12/2014] [Accepted: 09/13/2014] [Indexed: 11/19/2022]
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10
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Haldar S, Sengupta S. Plant-microbe Cross-talk in the Rhizosphere: Insight and Biotechnological Potential. Open Microbiol J 2015; 9:1-7. [PMID: 25926899 PMCID: PMC4406998 DOI: 10.2174/1874285801509010001] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/27/2015] [Accepted: 01/30/2015] [Indexed: 11/22/2022] Open
Abstract
Rhizosphere, the interface between soil and plant roots, is a chemically complex environment which supports the development and growth of diverse microbial communities. The composition of the rhizosphere microbiome is dynamic and controlled by multiple biotic and abiotic factors that include environmental parameters, physiochemical properties of the soil, biological activities of the plants and chemical signals from the plants and bacteria which inhabit the soil adherent to root-system. Recent advancement in molecular and microbiological techniques has unravelled the interactions among rhizosphere residents at different levels. In this review, we elaborate on various factors that determine plant-microbe and microbe-microbe interactions in the rhizosphere, with an emphasis on the impact of host genotype and developmental stages which together play pivotal role in shaping the nature and diversity of root exudations. We also discuss about the coherent functional groups of microorganisms that colonize rhizosphere and enhance plant growth and development by several direct and indirect mechanisms. Insights into the underlying structural principles of indigenous microbial population and the key determinants governing rhizosphere ecology will provide directions for developing techniques for profitable applicability of beneficial microorganisms in sustainable agriculture and nature restoration.
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Affiliation(s)
- Shyamalina Haldar
- Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata-700019, India
| | - Sanghamitra Sengupta
- Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata-700019, India
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Guazzaroni ME, Silva-Rocha R, Ward RJ. Synthetic biology approaches to improve biocatalyst identification in metagenomic library screening. Microb Biotechnol 2014; 8:52-64. [PMID: 25123225 PMCID: PMC4321373 DOI: 10.1111/1751-7915.12146] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 06/22/2014] [Accepted: 06/28/2014] [Indexed: 11/28/2022] Open
Abstract
There is a growing demand for enzymes with improved catalytic performance or tolerance to process-specific parameters, and biotechnology plays a crucial role in the development of biocatalysts for use in industry, agriculture, medicine and energy generation. Metagenomics takes advantage of the wealth of genetic and biochemical diversity present in the genomes of microorganisms found in environmental samples, and provides a set of new technologies directed towards screening for new catalytic activities from environmental samples with potential biotechnology applications. However, biased and low level of expression of heterologous proteins in Escherichia coli together with the use of non-optimal cloning vectors for the construction of metagenomic libraries generally results in an extremely low success rate for enzyme identification. The bottleneck arising from inefficient screening of enzymatic activities has been addressed from several perspectives; however, the limitations related to biased expression in heterologous hosts cannot be overcome by using a single approach, but rather requires the synergetic implementation of multiple methodologies. Here, we review some of the principal constraints regarding the discovery of new enzymes in metagenomic libraries and discuss how these might be resolved by using synthetic biology methods.
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12
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Evaluation of a pooled strategy for high-throughput sequencing of cosmid clones from metagenomic libraries. PLoS One 2014; 9:e98968. [PMID: 24911009 PMCID: PMC4049660 DOI: 10.1371/journal.pone.0098968] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 05/09/2014] [Indexed: 11/19/2022] Open
Abstract
High-throughput sequencing methods have been instrumental in the growing field of metagenomics, with technological improvements enabling greater throughput at decreased costs. Nonetheless, the economy of high-throughput sequencing cannot be fully leveraged in the subdiscipline of functional metagenomics. In this area of research, environmental DNA is typically cloned to generate large-insert libraries from which individual clones are isolated, based on specific activities of interest. Sequence data are required for complete characterization of such clones, but the sequencing of a large set of clones requires individual barcode-based sample preparation; this can become costly, as the cost of clone barcoding scales linearly with the number of clones processed, and thus sequencing a large number of metagenomic clones often remains cost-prohibitive. We investigated a hybrid Sanger/Illumina pooled sequencing strategy that omits barcoding altogether, and we evaluated this strategy by comparing the pooled sequencing results to reference sequence data obtained from traditional barcode-based sequencing of the same set of clones. Using identity and coverage metrics in our evaluation, we show that pooled sequencing can generate high-quality sequence data, without producing problematic chimeras. Though caveats of a pooled strategy exist and further optimization of the method is required to improve recovery of complete clone sequences and to avoid circumstances that generate unrecoverable clone sequences, our results demonstrate that pooled sequencing represents an effective and low-cost alternative for sequencing large sets of metagenomic clones.
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Versatile broad-host-range cosmids for construction of high quality metagenomic libraries. J Microbiol Methods 2014; 99:27-34. [PMID: 24495694 DOI: 10.1016/j.mimet.2014.01.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/22/2014] [Accepted: 01/25/2014] [Indexed: 12/18/2022]
Abstract
We constructed IncP broad-host-range Gateway® entry cosmids pJC8 and pJC24, which replicate in diverse Proteobacteria. We demonstrate the functionality of these vectors by extracting, purifying, and size-selecting metagenomic DNA from agricultural corn and wheat soils, followed by cloning into pJC8. Metagenomic DNA libraries of 8×10(4) (corn soil) and 9×10(6) (wheat soil) clones were generated for functional screening. The DNA cloned in these libraries can be transferred from these recombinant cosmids to Gateway® destination vectors for specialized screening purposes. Those library clones are available from the Canadian MetaMicroBiome Library project (http://www.cm2bl.org/).
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Lee MH, Lee SW. Bioprospecting potential of the soil metagenome: novel enzymes and bioactivities. Genomics Inform 2013; 11:114-20. [PMID: 24124406 PMCID: PMC3794083 DOI: 10.5808/gi.2013.11.3.114] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/14/2013] [Accepted: 08/20/2013] [Indexed: 11/22/2022] Open
Abstract
The microbial diversity in soil ecosystems is higher than in any other microbial ecosystem. The majority of soil microorganisms has not been characterized, because the dominant members have not been readily culturable on standard cultivation media; therefore, the soil ecosystem is a great reservoir for the discovery of novel microbial enzymes and bioactivities. The soil metagenome, the collective microbial genome, could be cloned and sequenced directly from soils to search for novel microbial resources. This review summarizes the microbial diversity in soils and the efforts to search for microbial resources from the soil metagenome, with more emphasis on the potential of bioprospecting metagenomics and recent discoveries.
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Affiliation(s)
- Myung Hwan Lee
- Department of Applied Biology, Dong-A University, Busan 604-714, Korea
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16
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Geddes BA, Oresnik IJ. Genetic characterization of a complex locus necessary for the transport and catabolism of erythritol, adonitol and L-arabitol in Sinorhizobium meliloti. MICROBIOLOGY-SGM 2012; 158:2180-2191. [PMID: 22609752 DOI: 10.1099/mic.0.057877-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Sinorhizobium meliloti locus necessary for the utilization of erythritol as a sole carbon source, contains 17 genes, including genes that encode an ABC transporter necessary for the transport of erythritol, as well as the genes encoding EryA, EryB, EryC, TpiB and the regulators EryD and EryR (SMc01615). Construction of defined deletions and complementation experiments show that the other genes at this locus encode products that are necessary for the catabolism of adonitol (ribitol) and l-arabitol, but not d-arabitol. These analyses show that aside from one gene that is specific for the catabolism of l-arabitol (SMc01619, lalA), the rest of the catabolic genes are necessary for both polyols (SMc01617, rbtC; SMc01618, rbtB; SMc01622, rbtA). Genetic and biochemical data show that in addition to utilizing erythritol as a substrate, EryA is also capable of utilizing adonitol and l-arabitol. Similarly, transport experiments using labelled erythritol show that adonitol, l-arabitol and erythritol share a common transporter (MptABCDE). Quantitative RT-PCR experiments show that transcripts containing genes necessary for adonitol and l-arabitol utilization are induced by these sugars in an eryA-dependent manner.
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Affiliation(s)
- Barney A Geddes
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Ivan J Oresnik
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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Neufeld JD, Engel K, Cheng J, Moreno-Hagelsieb G, Rose DR, Charles TC. Open resource metagenomics: a model for sharing metagenomic libraries. Stand Genomic Sci 2011; 5:203-10. [PMID: 22180823 PMCID: PMC3235511 DOI: 10.4056/sigs.1974654] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Both sequence-based and activity-based exploitation of environmental DNA have provided unprecedented access to the genomic content of cultivated and uncultivated microorganisms. Although researchers deposit microbial strains in culture collections and DNA sequences in databases, activity-based metagenomic studies typically only publish sequences from the hits retrieved from specific screens. Physical metagenomic libraries, conceptually similar to entire sequence datasets, are usually not straightforward to obtain by interested parties subsequent to publication. In order to facilitate unrestricted distribution of metagenomic libraries, we propose the adoption of open resource metagenomics, in line with the trend towards open access publishing, and similar to culture- and mutant-strain collections that have been the backbone of traditional microbiology and microbial genetics. The concept of open resource metagenomics includes preparation of physical DNA libraries, preferably in versatile vectors that facilitate screening in a diversity of host organisms, and pooling of clones so that single aliquots containing complete libraries can be easily distributed upon request. Database deposition of associated metadata and sequence data for each library provides researchers with information to select the most appropriate libraries for further research projects. As a starting point, we have established the Canadian MetaMicroBiome Library (CM(2)BL [1]). The CM(2)BL is a publicly accessible collection of cosmid libraries containing environmental DNA from soils collected from across Canada, spanning multiple biomes. The libraries were constructed such that the cloned DNA can be easily transferred to Gateway® compliant vectors, facilitating functional screening in virtually any surrogate microbial host for which there are available plasmid vectors. The libraries, which we are placing in the public domain, will be distributed upon request without restriction to members of both the academic research community and industry. This article invites the scientific community to adopt this philosophy of open resource metagenomics to extend the utility of functional metagenomics beyond initial publication, circumventing the need to start from scratch with each new research project.
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Schallmey M, Ly A, Wang C, Meglei G, Voget S, Streit WR, Driscoll BT, Charles TC. Harvesting of novel polyhydroxyalkanaote (PHA) synthase encoding genes from a soil metagenome library using phenotypic screening. FEMS Microbiol Lett 2011; 321:150-6. [DOI: 10.1111/j.1574-6968.2011.02324.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Parachin NS, Gorwa-Grauslund MF. Isolation of xylose isomerases by sequence- and function-based screening from a soil metagenomic library. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:9. [PMID: 21545702 PMCID: PMC3113934 DOI: 10.1186/1754-6834-4-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 05/05/2011] [Indexed: 05/15/2023]
Abstract
BACKGROUND Xylose isomerase (XI) catalyses the isomerisation of xylose to xylulose in bacteria and some fungi. Currently, only a limited number of XI genes have been functionally expressed in Saccharomyces cerevisiae, the microorganism of choice for lignocellulosic ethanol production. The objective of the present study was to search for novel XI genes in the vastly diverse microbial habitat present in soil. As the exploitation of microbial diversity is impaired by the ability to cultivate soil microorganisms under standard laboratory conditions, a metagenomic approach, consisting of total DNA extraction from a given environment followed by cloning of DNA into suitable vectors, was undertaken. RESULTS A soil metagenomic library was constructed and two screening methods based on protein sequence similarity and enzyme activity were investigated to isolate novel XI encoding genes. These two screening approaches identified the xym1 and xym2 genes, respectively. Sequence and phylogenetic analyses revealed that the genes shared 67% similarity and belonged to different bacterial groups. When xym1 and xym2 were overexpressed in a xylA-deficient Escherichia coli strain, similar growth rates to those in which the Piromyces XI gene was expressed were obtained. However, expression in S. cerevisiae resulted in only one-fourth the growth rate of that obtained for the strain expressing the Piromyces XI gene. CONCLUSIONS For the first time, the screening of a soil metagenomic library in E. coli resulted in the successful isolation of two active XIs. However, the discrepancy between XI enzyme performance in E. coli and S. cerevisiae suggests that future screening for XI activity from soil should be pursued directly using yeast as a host.
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Affiliation(s)
- Nádia Skorupa Parachin
- Department of Applied Microbiology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
- Present affiliation - Laboratório de Biologia Molecular, Universidade de Brasília, 70910-900 Brasília (DF), Brazil
| | - Marie F Gorwa-Grauslund
- Department of Applied Microbiology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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20
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Abstract
We describe how wide host-range cloning vectors can lead to more flexible and effective procedures to isolate novel genes by screening metagenomic libraries in a range of bacterial hosts, not just the conventionally used Escherichia coli. We give examples of various wide host-range plasmid, cosmid, and BAC cloning vectors and the types of genes and activities that have been successfully obtained to date. We present a detailed protocol that involves the construction and screening of a metagenomic library comprising fragments of bacterial DNA, obtained from a wastewater treatment plant and cloned in a wide host-range cosmid. We also consider future prospects and how techniques and tools can be improved.
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Affiliation(s)
- Margaret Wexler
- School of Biological Sciences, University of East Anglia, Norwich, Norfolk, UK
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21
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Troeschel SC, Drepper T, Leggewie C, Streit WR, Jaeger KE. Novel tools for the functional expression of metagenomic DNA. Methods Mol Biol 2011; 668:117-39. [PMID: 20830560 DOI: 10.1007/978-1-60761-823-2_8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
The functional expression of environmental genes in a particular host bacterium is hampered by various limitations including inefficient transcription of target genes as well as improper assembly of the corresponding enzymes. Therefore, the identification of novel enzymes from metagenomic libraries by activity-based screening requires efficient expression and screening systems. In the following chapter, we present two novel tools to improve the functional expression of metagenomic genes. (1) Comparative screenings of metagenomic libraries demonstrated that different enzymes were detected when phylogenetically distinct expression host strains were used. Thus, we have developed a strategy, which comprises library construction using a shuttle vector that allows comparative expression and screening of metagenomic DNA in Escherichia coli, Pseudomonas putida, and Bacillus subtilis. (2) Expression studies have revealed that functional expression of environmental genes in heterologous expression hosts is often limited by insufficient promoter recognition. Therefore, a method is described allowing to enhance the expression capacity of E. coli by using the transposon MuExpress. This recombinant transposon is able to insert randomly into environmental DNA fragments thereby facilitating gene expression from its two inducible promoters.
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Affiliation(s)
- Sonja Christina Troeschel
- Research Centre Juelich, Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Juelich, Germany
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22
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Abstract
Metagenomics has revolutionized microbiology by paving the way for a cultivation-independent assessment and exploitation of microbial communities present in complex ecosystems. Metagenomics comprising construction and screening of metagenomic DNA libraries has proven to be a powerful tool to isolate new enzymes and drugs of industrial importance. So far, the majority of the metagenomically exploited habitats comprised temperate environments, such as soil and marine environments. Recently, metagenomes of extreme environments have also been used as sources of novel biocatalysts. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body, and ocean water. Analyses of these data sets opened a window into the enormous taxonomic and functional diversity of environmental microbial communities. To assess the functional dynamics of microbial communities, metatranscriptomics and metaproteomics have been developed. The combination of DNA-based, mRNA-based, and protein-based analyses of microbial communities present in different environments is a way to elucidate the compositions, functions, and interactions of microbial communities and to link these to environmental processes.
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23
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Abstract
Metagenomics has revolutionized microbiology by paving the way for a cultivation-independent assessment and exploitation of microbial communities present in complex ecosystems. Metagenomics comprising construction and screening of metagenomic DNA libraries has proven to be a powerful tool to isolate new enzymes and drugs of industrial importance. So far, the majority of the metagenomically exploited habitats comprised temperate environments, such as soil and marine environments. Recently, metagenomes of extreme environments have also been used as sources of novel biocatalysts. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body, and ocean water. Analyses of these data sets opened a window into the enormous taxonomic and functional diversity of environmental microbial communities. To assess the functional dynamics of microbial communities, metatranscriptomics and metaproteomics have been developed. The combination of DNA-based, mRNA-based, and protein-based analyses of microbial communities present in different environments is a way to elucidate the compositions, functions, and interactions of microbial communities and to link these to environmental processes.
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24
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Zhu SW, Fang ZY, Jiang HY, Cheng BJ. Molecular and functional analysis of the poly-β-hydroxybutyrate biosynthesis operon of Pseudomonas sp BJ-1. GENETICS AND MOLECULAR RESEARCH 2010; 9:2349-56. [PMID: 21157703 DOI: 10.4238/vol9-4gmr845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The operon comprising the genes for poly-β-hydroxybutyrate (PHB) biosynthesis in Pseudomonas sp BJ-1 was cloned and sequenced. Sequence analysis of 8991 bp revealed that the regions contain two related operons. The first operon contains the three genes phbA, phbB and phbC, and the other contains the two genes flp1 and flp2. The deduced amino acid sequences of PHBA and PHBB showed high identity with other bacterial PHB genes. Transcription of the three genes of the first operon is controlled by a single hypothetical promoter region, whereas the other two flp genes are controlled by two hypothetical promoter regions. Analysis of expressed protein at different times showed that PHBA protein levels increased from 0 to 4 h; PHBB and PHBC showed similar kinetics. Detection of enzyme activity showed three proteins with bioactivity and biological function in the synthesis of PHB intermediates.
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Affiliation(s)
- S W Zhu
- School of Life Science, Anhui Agricultural University, Hefei, China
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25
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Kakirde KS, Parsley LC, Liles MR. Size Does Matter: Application-driven Approaches for Soil Metagenomics. SOIL BIOLOGY & BIOCHEMISTRY 2010; 42:1911-1923. [PMID: 21076656 PMCID: PMC2976544 DOI: 10.1016/j.soilbio.2010.07.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Metagenomic analyses can provide extensive information on the structure, composition, and predicted gene functions of diverse environmental microbial assemblages. Each environment presents its own unique challenges to metagenomic investigation and requires a specifically designed approach to accommodate physicochemical and biotic factors unique to each environment that can pose technical hurdles and/or bias the metagenomic analyses. In particular, soils harbor an exceptional diversity of prokaryotes that are largely undescribed beyond the level of ribotype and are a potentially vast resource for natural product discovery. The successful application of a soil metagenomic approach depends on selecting the appropriate DNA extraction, purification, and if necessary, cloning methods for the intended downstream analyses. The most important technical considerations in a metagenomic study include obtaining a sufficient yield of high-purity DNA representing the targeted microorganisms within an environmental sample or enrichment and (if required) constructing a metagenomic library in a suitable vector and host. Size does matter in the context of the average insert size within a clone library or the sequence read length for a high-throughput sequencing approach. It is also imperative to select the appropriate metagenomic screening strategy to address the specific question(s) of interest, which should drive the selection of methods used in the earlier stages of a metagenomic project (e.g., DNA size, to clone or not to clone). Here, we present both the promising and problematic nature of soil metagenomics and discuss the factors that should be considered when selecting soil sampling, DNA extraction, purification, and cloning methods to implement based on the ultimate study objectives.
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Affiliation(s)
- Kavita S Kakirde
- Department of Biological Sciences, Auburn University, Auburn, AL 36849
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26
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Geddes BA, Pickering BS, Poysti NJ, Collins H, Yudistira H, Oresnik IJ. A locus necessary for the transport and catabolism of erythritol in Sinorhizobium meliloti. Microbiology (Reading) 2010; 156:2970-2981. [PMID: 20671019 DOI: 10.1099/mic.0.041905-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this work we have genetically defined an erythritol utilization locus in Sinorhizobium meliloti. A cosmid containing the locus was isolated by complementation of a transposon mutant and was subsequently mutagenized using Tn5 : : B20. The locus was found to consist of five transcriptional units, each of which was necessary for the utilization of erythritol. Genetic complementation experiments using genes putatively annotated as erythritol catabolic genes clearly showed that, of the 17 genes at this locus, six genes are not necessary for the utilization of erythritol as a sole carbon source. The remaining genes encode EryA, EryB, EryC and TpiB as well as an uncharacterized ABC-type transporter. Transport experiments using labelled erythritol showed that components of the ABC transporter are necessary for the uptake of erythritol. The locus also contains two regulators: EryD, a SorC class regulator, and SMc01615, a DeoR class regulator. Quantitative RT-PCR experiments showed that each of these regulators negatively regulates its own transcription. In addition, induction of the erythritol locus was dependent upon EryD and a product of erythritol catabolism. Further characterization of polar mutations revealed that in addition to erythritol, the locus contains determinants for adonitol and l-arabitol utilization. The context of the mutations suggests that the locus is important for both the transport and catabolism of adonitol and l-arabitol.
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Affiliation(s)
- Barney A. Geddes
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Brad S. Pickering
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Nathan J. Poysti
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Heather Collins
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Harry Yudistira
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Ivan J. Oresnik
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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27
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Hölscher T, Breuer U, Adrian L, Harms H, Maskow T. Production of the chiral compound (R)-3-hydroxybutyrate by a genetically engineered methylotrophic bacterium. Appl Environ Microbiol 2010; 76:5585-91. [PMID: 20581197 PMCID: PMC2918973 DOI: 10.1128/aem.01065-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 06/11/2010] [Indexed: 11/20/2022] Open
Abstract
In this study, a methylotrophic bacterium, Methylobacterium rhodesianum MB 126, was used for the production of the chiral compound (R)-3-hydroxybutyrate (R-3HB) from methanol. R-3HB is formed during intracellular degradation of the storage polymer (R)-3-polyhydroxybutyrate (PHB). Since the monomer R-3HB does not accumulate under natural conditions, M. rhodesianum was genetically modified. The gene (hbd) encoding the R-3HB-degrading enzyme, R-3HB dehydrogenase, was inactivated in M. rhodesianum. The resulting hbd mutant still exhibited low growth rates on R-3HB as the sole source of carbon and energy, indicating the presence of alternative pathways for R-3HB utilization. Therefore, transposon mutagenesis was carried out with the hbd mutant, and a double mutant unable to grow on R-3HB was obtained. This mutant was shown to be defective in lipoic acid synthase (LipA), resulting in an incomplete citric acid cycle. Using the hbd lipA mutant, we produced 3.2 to 3.5 mM R-3HB in batch and 27 mM (2,800 mg liter(-1)) in fed-batch cultures. This was achieved by sequences of cultivation conditions initially favoring growth, then PHB accumulation, and finally PHB degradation.
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Affiliation(s)
- Tina Hölscher
- UFZ-Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
| | - Uta Breuer
- UFZ-Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
| | - Lorenz Adrian
- UFZ-Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
| | - Hauke Harms
- UFZ-Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
| | - Thomas Maskow
- UFZ-Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
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28
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Nordeste RF, Trainer MA, Charles TC. Methods for the isolation of genes encoding novel PHB cycle enzymes from complex microbial communities. Methods Mol Biol 2010; 668:235-246. [PMID: 20830568 DOI: 10.1007/978-1-60761-823-2_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Development of different PHAs as alternatives to petrochemically derived plastics can be facilitated by mining metagenomic libraries for diverse PHA cycle genes that might be useful for synthesis of bioplastics. The specific phenotypes associated with mutations of the PHA synthesis pathway genes in Sinorhizobium meliloti allows for the use of powerful selection and screening tools to identify complementing novel PHA synthesis genes. Identification of novel genes through their function rather than sequence facilitates finding functional proteins that may otherwise have been excluded through sequence-only screening methodology. We present here methods that we have developed for the isolation of clones expressing novel PHA metabolism genes from metagenomic libraries.
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29
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Jach G, Soezer N, Schullehner K, Lalla B, Welters P, Mueller A. Phytomining of plant enzymes for biotechnological use of fats and oils. EUR J LIPID SCI TECH 2010. [DOI: 10.1002/ejlt.200900100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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30
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Functional metagenomics for enzyme discovery: challenges to efficient screening. Curr Opin Biotechnol 2009; 20:616-22. [DOI: 10.1016/j.copbio.2009.09.010] [Citation(s) in RCA: 244] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/18/2009] [Accepted: 09/25/2009] [Indexed: 11/17/2022]
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31
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Simon C, Daniel R. Achievements and new knowledge unraveled by metagenomic approaches. Appl Microbiol Biotechnol 2009; 85:265-76. [PMID: 19760178 PMCID: PMC2773367 DOI: 10.1007/s00253-009-2233-z] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 08/25/2009] [Accepted: 08/25/2009] [Indexed: 02/01/2023]
Abstract
Metagenomics has paved the way for cultivation-independent assessment and exploitation of microbial communities present in complex ecosystems. In recent years, significant progress has been made in this research area. A major breakthrough was the improvement and development of high-throughput next-generation sequencing technologies. The application of these technologies resulted in the generation of large datasets derived from various environments such as soil and ocean water. The analyses of these datasets opened a window into the enormous phylogenetic and metabolic diversity of microbial communities living in a variety of ecosystems. In this way, structure, functions, and interactions of microbial communities were elucidated. Metagenomics has proven to be a powerful tool for the recovery of novel biomolecules. In most cases, functional metagenomics comprising construction and screening of complex metagenomic DNA libraries has been applied to isolate new enzymes and drugs of industrial importance. For this purpose, several novel and improved screening strategies that allow efficient screening of large collections of clones harboring metagenomes have been introduced.
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Affiliation(s)
- Carola Simon
- Department of Genomic and Applied Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Grisebachstr 8, 37077 Göttingen, Germany
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32
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Hao Y, Winans SC, Glick BR, Charles TC. Identification and characterization of new LuxR/LuxI-type quorum sensing systems from metagenomic libraries. Environ Microbiol 2009; 12:105-17. [PMID: 19735279 DOI: 10.1111/j.1462-2920.2009.02049.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Quorum sensing (QS) cell-cell communication systems are utilized by bacteria to coordinate their behaviour according to cell density. Several different types of QS signal molecules have been identified, among which acyl-homoserine lactones (AHLs) produced by Proteobacteria have been studied to the greatest extent. Although QS has been studied extensively in cultured microorganisms, little is known about the QS systems of uncultured microorganisms and the roles of these systems in microbial communities. To extend our knowledge of QS systems and to better understand the signalling that takes place in the natural environment, metagenomic libraries constructed using DNA from activated sludge and soil were screened, using an Agrobacterium biosensor strain, for novel QS synthase genes. Three cosmids (QS6-1, QS10-1 and QS10-2) that encode the production of QS signals were identified and DNA sequence analysis revealed that all three clones encode a novel luxI family AHL synthase and a luxR family transcriptional regulator. Thin layer chromatography revealed that these LuxI homologue proteins are able to synthesize multiple AHL signals. Tandem mass spectrometry analysis revealed that LuxI(QS6-1) directs the synthesis of at least three AHLs, 3-O-C14:1 HSL, 3-O-C16:1 HSL and 3-O-C14 HSL; LuxI(QS10-1) directs the synthesis of at least 3-O-C12 HSL and 3-O-C14 HSL; while LuxI(QS10-2) directs the synthesis of at least C8 HSL and C10 HSL. Two possible new AHLs, C14:3 HSL and (?)-hydroxymethyl-3-O-C14 HSL, were also found to be synthesized by LuxI(QS6-1).
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Affiliation(s)
- Youai Hao
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
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33
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Rapid identification of genes encoding DNA polymerases by function-based screening of metagenomic libraries derived from glacial ice. Appl Environ Microbiol 2009; 75:2964-8. [PMID: 19270136 DOI: 10.1128/aem.02644-08] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Small-insert and large-insert metagenomic libraries were constructed from glacial ice of the Northern Schneeferner, which is located on the Zugspitzplatt in Germany. Subsequently, these libraries were screened for the presence of DNA polymerase-encoding genes by complementation of an Escherichia coli polA mutant. Nine novel genes encoding complete DNA polymerase I proteins or domains typical of these proteins were recovered.
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Jacob AI, Adham SAI, Capstick DS, Clark SRD, Spence T, Charles TC. Mutational analysis of the Sinorhizobium meliloti short-chain dehydrogenase/reductase family reveals substantial contribution to symbiosis and catabolic diversity. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:979-87. [PMID: 18533838 DOI: 10.1094/mpmi-21-7-0979] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The short-chain dehydrogenase/reductase (SDR) family is one of the largest and most ubiquitous protein families in bacterial genomes. Despite there being a few well-characterized examples, the substrate specificities or functions of most members of the family are unknown. In this study, we carried out a large-scale mutagenesis of the SDR gene family in the alfalfa root nodule symbiont Sinorhizobium meliloti. Subsequent phenotypic analysis revealed phenotypes for mutants of 21 of the SDR-encoding genes. This brings the total number of S. meliloti SDR-encoding genes with known function or associated phenotype to 25. Several of the mutants were deficient in the utilization of specific carbon sources, while others exhibited symbiotic deficiencies on alfalfa (Medicago sativa), ranging from partial ineffectiveness to complete inability to form root nodules. Five of the mutants had both symbiotic and carbon utilization phenotypes. These results clearly demonstrate the importance of the SDR family in both symbiosis and saprotrophy, and reinforce the complex nature of the interaction of S. meliloti with its plant hosts. Further analysis of the genes identified in this study will contribute to the overall understanding of the biology and metabolism of S. meliloti in relation to its interaction with alfalfa.
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Affiliation(s)
- Asha I Jacob
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
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35
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Influence of the poly-3-hydroxybutyrate (PHB) granule-associated proteins (PhaP1 and PhaP2) on PHB accumulation and symbiotic nitrogen fixation in Sinorhizobium meliloti Rm1021. J Bacteriol 2007; 189:9050-6. [PMID: 17921298 DOI: 10.1128/jb.01190-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sinorhizobium meliloti cells store excess carbon as intracellular poly-3-hydroxybutyrate (PHB) granules that assist survival under fluctuating nutritional conditions. PHB granule-associated proteins (phasins) are proposed to regulate PHB synthesis and granule formation. Although the enzymology and genetics of PHB metabolism in S. meliloti have been well characterized, phasins have not yet been described for this organism. Comparison of the protein profiles of the wild type and a PHB synthesis mutant revealed two major proteins absent from the mutant. These were identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) as being encoded by the SMc00777 (phaP1) and SMc02111 (phaP2) genes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins associated with PHB granules followed by MALDI-TOF confirmed that PhaP1 and PhaP2 were the two major phasins. Double mutants were defective in PHB production, while single mutants still produced PHB, and unlike PHB synthesis mutants that have reduced exopolysaccharide, the double mutants had higher exopolysaccharide levels. Medicago truncatula plants inoculated with the double mutant exhibited reduced shoot dry weight (SDW), although there was no corresponding reduction in nitrogen fixation activity. Whether the phasins are involved in a metabolic regulatory response or whether the reduced SDW is due to a reduction in assimilation of fixed nitrogen rather than a reduction in nitrogen fixation activity remains to be established.
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36
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Schmeisser C, Steele H, Streit WR. Metagenomics, biotechnology with non-culturable microbes. Appl Microbiol Biotechnol 2007; 75:955-62. [PMID: 17396253 DOI: 10.1007/s00253-007-0945-5] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2007] [Revised: 03/12/2007] [Accepted: 03/12/2007] [Indexed: 10/23/2022]
Abstract
Metagenomics as a new field of research has been developed over the past decade to elucidate the genomes of the non-cultured microbes with the goal to better understand global microbial ecology on the one side, and on the other side it has been driven by the increasing biotechnological demands for novel enzymes and biomolecules. Since it is well accepted that the majority of all microbes has not yet been cultured, the not-yet-cultivated microbes represent a shear unlimited and intriguing resource for the development of novel genes, enzymes and chemical compounds for use in biotechnology. However, with respect to biotechnology, metagenomics faces now two major challenges. Firstly, it has to identify truly novel biocatalysts to fulfil the needs of industrial processes and green chemistry. Secondly, the already available genes and enzymes need to be implemented in production processes to further prove the value of metagenome-derived sequences.
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Affiliation(s)
- Christel Schmeisser
- Abteilung für Mikrobiologie und Biotechnologie, Biozentrum Klein-Flottbek, Universität Hamburg, Ohnhorststrasse 18, 22609, Hamburg, Germany
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37
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Crocker FH, Indest KJ, Fredrickson HL. Biodegradation of the cyclic nitramine explosives RDX, HMX, and CL-20. Appl Microbiol Biotechnol 2006; 73:274-90. [PMID: 17058075 DOI: 10.1007/s00253-006-0588-y] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Revised: 07/19/2006] [Accepted: 08/07/2006] [Indexed: 10/24/2022]
Abstract
Cyclic nitramine explosives are synthesized globally mainly as military munitions, and their use has resulted in environmental contamination. Several biodegradation pathways have been proposed, and these are based mainly on end-product characterization because many of the metabolic intermediates are hypothetical and unstable in water. Biodegradation mechanisms for cyclic nitramines include (a) formation of a nitramine free radical and loss of nitro functional groups, (b) reduction of nitro functional groups, (c) direct enzymatic cleavage, (d) alpha-hydroxylation, or (e) hydride ion transfer. Pathway intermediates spontaneously decompose in water producing nitrite, nitrous oxide, formaldehyde, or formic acid as common end-products. In vitro enzyme and functional gene expression studies have implicated a limited number of enzymes/genes involved in cyclic nitramine catabolism. Advances in molecular biology methods such as high-throughput DNA sequencing, microarray analysis, and nucleic acid sample preparation are providing access to biochemical and genetic information on cultivable and uncultivable microorganisms. This information can provide the knowledge base for rational engineering of bioremediation strategies, biosensor development, environmental monitoring, and green biosynthesis of explosives. This paper reviews recent developments on the biodegradation of cyclic nitramines and the potential of genomics to identify novel functional genes of explosive metabolism.
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Affiliation(s)
- Fiona H Crocker
- US Army Engineer Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA.
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