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Yu F, Bobashev G, Bienkowski PR, Sayler GS. Artificial Neural Network Modeling on Trichloroethylene Biodegradation in a Packed-Bed Biofilm Reactor and Its Comparison with Response Surface Modeling Approach. Biochem Eng J 2022. [DOI: 10.1016/j.bej.2022.108801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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2
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Aukema KG, Bygd MD, Tassoulas LJ, Richman JE, Wackett LP. Fluoro-recognition: New in vivo fluorescent assay for toluene dioxygenase probing induction by and metabolism of polyfluorinated compounds. Environ Microbiol 2022; 24:5202-5216. [PMID: 36054238 PMCID: PMC9828342 DOI: 10.1111/1462-2920.16187] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 08/30/2022] [Indexed: 01/12/2023]
Abstract
The present study examined the regulatory and metabolic response of the aromatic degrader Pseudomonas putida F1 and its tod operon, controlling toluene degradation, to fluorinated aromatic and aliphatic compounds. The tod operon is upregulated by inducer binding to the TodS sensing domain of a two-component regulator. The induced enzymes include toluene dioxygenase that initiates catabolic assimilation of benzenoid hydrocarbons. Toluene dioxygenase was shown to oxidize 6-fluoroindole to a meta-stable fluorescent product, 6-fluoroindoxyl. The fluorescent output allowed monitoring relative levels of tod operon induction in whole cells using microtiter well plates. Mono- and polyfluorinated aromatic compounds were shown to induce toluene dioxygenase, in some cases to a greater extent than compounds serving as growth substrates. Compounds that are oxidized by toluene dioxygenase and undergoing defluorination were shown to induce their own metabolism. 1,2,4-Trifluorobenzene caused significant induction and computational modelling indicated productive binding to the TodS sensor domain of the TodST regulator. Toluene dioxygenase also showed preferential binding of 1,2,4-trifluorobenzene such that defluorination was favoured. Fluorinated aliphatic compounds were shown to induce toluene dioxygenase. An aliphatic ether with seven fluorine atoms, 1,1,1,2-tetrafluoro-2-trifluoromethoxy-4-iodobutane (TTIB), was an excellent inducer of toluene dioxygenase activity and shown to undergo transformation in cultures of P. putida F1.
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Affiliation(s)
- Kelly G. Aukema
- Department of Biochemistry, Molecular Biology and Biophysics and Biotechnology InstituteUniversity of Minnesota, Twin CitiesMinnesotaUSA
| | - Madison D. Bygd
- Department of Biochemistry, Molecular Biology and Biophysics and Biotechnology InstituteUniversity of Minnesota, Twin CitiesMinnesotaUSA
| | - Lambros J. Tassoulas
- Department of Biochemistry, Molecular Biology and Biophysics and Biotechnology InstituteUniversity of Minnesota, Twin CitiesMinnesotaUSA
| | - Jack E. Richman
- Department of Biochemistry, Molecular Biology and Biophysics and Biotechnology InstituteUniversity of Minnesota, Twin CitiesMinnesotaUSA
| | - Lawrence P. Wackett
- Department of Biochemistry, Molecular Biology and Biophysics and Biotechnology InstituteUniversity of Minnesota, Twin CitiesMinnesotaUSA
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Yu F, Munoz B, Bienkowski PR, Sayler GS. Bayesian estimation and sensitivity analysis of toluene and trichloroethylene biodegradation kinetic parameters. JOURNAL OF ENVIRONMENTAL QUALITY 2020; 49:640-653. [PMID: 33016407 DOI: 10.1002/jeq2.20064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/30/2020] [Accepted: 02/11/2020] [Indexed: 06/11/2023]
Abstract
Parameter estimation is needed for process management, design, and reactor scaling when values from the literature vary tremendously or are unavailable. A Bayesian approach, implemented via Markov chain Monte Carlo (MCMC) simulations using SAS software, was used to estimate the kinetic parameters of toluene and trichloroethylene (TCE) biodegradation by the microorganism Pseudomonas putida F1 in batch cultures. The prediction capabilities of Bayesian estimation were illustrated by comparing predicted and observed data and reported in goodness-of-fit statistics. The sensitivity analysis showed that the parameters obtained using this approach were consistent under the designated toluene and TCE concentration range. Moreover, the impact of TCE on toluene degradation kinetics was numerically exhibited, verifying the fact that TCE was able to stimulate toluene degradation; hence, TCE's presence increased the apparent maximum toluene-specific rate. Various kinetic models were explored at different degrees of complexity. At a low TCE concentration range (e.g., <2 mg L-1 ), a simplified Michaelis-Menten model (i.e., substrate half-saturation parameters approximated the inhibition parameters) was adequate to describe the reaction kinetics. However, at a higher TCE range (e.g., 5 mg L-1 ), a full-scale Michaelis-Menten model was needed to discriminate among the inhibition parameters in the model. The results demonstrated that a Bayesian estimation method is particularly useful for determining complex bioreaction kinetic parameters in the presence of a small volume of experimental data.
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Affiliation(s)
- Feng Yu
- RTI International, 3040 Cornwallis Rd., Research Triangle Park, NC, 27709, USA
| | - Breda Munoz
- RTI International, 3040 Cornwallis Rd., Research Triangle Park, NC, 27709, USA
| | - Paul R Bienkowski
- Dep. of Chemical and Biomolecular Engineering (retired), Univ. of Tennessee, Knoxville, TN, 37996, USA
| | - Gary S Sayler
- Center for Environmental Biotechnology, Univ. of Tennessee, Knoxville, TN, 37996, USA
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Ray S, Panjikar S, Anand R. Design of Protein-Based Biosensors for Selective Detection of Benzene Groups of Pollutants. ACS Sens 2018; 3:1632-1638. [PMID: 30084640 DOI: 10.1021/acssensors.8b00190] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Benzene and its derivatives form a class of priority pollutants whose exposure poses grave risk to human health. Since benzene lacks active functional groups, devising specific sensors for its direct detection from a milieu of aromatics has remained a daunting task. Here, we report three engineered protein-based biosensors that exclusively and specifically detect benzene and its derivatives up to a detection limit of 0.3 ppm. Further, the biosensor design has been engineered to create templates that possess the ability to specifically discriminate between alkyl substituted benzene derivatives; such as toluene, m-xylene, and mesitylene. Interference tests with simulated wastewater samples reveal that the engineered biosensors can selectively detect a specific benzene compound in water samples containing a milieu of high concentrations of commonly occurring pollutants. This work demonstrates the potential of structure guided protein engineering as a competent strategy toward design of selective biosensors for direct detection of benzene group of pollutants from real time environmental samples.
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Affiliation(s)
- Shamayeeta Ray
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, Maharashtra India
| | - Santosh Panjikar
- Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia
- Australian Synchrotron, Victoria 3168, Australia
| | - Ruchi Anand
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, Maharashtra India
- Wadhwani Research Center for Bioengineering, IIT Bombay, Mumbai 400076, India
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Jiang B, Huang WE, Li G. Construction of a bioreporter by heterogeneously expressing a Vibrio natriegens recA::luxCDABE fusion in Escherichia coli, and genotoxicity assessments of petrochemical-contaminated groundwater in northern China. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2016; 18:751-759. [PMID: 27258332 DOI: 10.1039/c6em00120c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Here, we constructed an Escherichia coli recA::luxCDABE bioreporter for genotoxicity assessments. The recA promoter was cloned from the marine bacterium Vibrio natriegens. This bioreporter showed a dose-response relationship following induction by mitomycin C, and other pollutants or environmental samples could be calculated as mitomycin C equivalents, which provided a way to quantitatively compare the genotoxicities of different environmental samples. This bioreporter was used to evaluate the genotoxicity under a wide range of external environmental conditions, like temperatures ranging from 15 °C to 42 °C, pH between 4.0 and 9.0, and salinity ranging from 0% to 3%. This successfully extended its application from the laboratory to the field, and allowed the bioreporter to assess the genotoxicity and bioavailability of genotoxins in various environmental media, including surface water, groundwater, seawater, and soil matrix. Expression of V. natriegens recA in E. coli indicated a LexA-like regulator in V. natriegens, and the putative SOS box of V. natriegens recA was similar to that of E. coli. The genotoxicities of groundwater samples from a petrochemical-contaminated site in northern China were evaluated by this bioreporter assay, and the genotoxic levels were in accordance with contamination levels obtained by chemical analyses.
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Affiliation(s)
- Bo Jiang
- School of Environment, Tsinghua University, Beijing, 100084, People's Republic of China.
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Xu T, Close D, Smartt A, Ripp S, Sayler G. Detection of organic compounds with whole-cell bioluminescent bioassays. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2014; 144:111-51. [PMID: 25084996 PMCID: PMC4597909 DOI: 10.1007/978-3-662-43385-0_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Natural and manmade organic chemicals are widely deposited across a diverse range of ecosystems including air, surface water, groundwater, wastewater, soil, sediment, and marine environments. Some organic compounds, despite their industrial values, are toxic to living organisms and pose significant health risks to humans and wildlife. Detection and monitoring of these organic pollutants in environmental matrices therefore is of great interest and need for remediation and health risk assessment. Although these detections have traditionally been performed using analytical chemical approaches that offer highly sensitive and specific identification of target compounds, these methods require specialized equipment and trained operators, and fail to describe potential bioavailable effects on living organisms. Alternatively, the integration of bioluminescent systems into whole-cell bioreporters presents a new capacity for organic compound detection. These bioreporters are constructed by incorporating reporter genes into catabolic or signaling pathways that are present within living cells and emit a bioluminescent signal that can be detected upon exposure to target chemicals. Although relatively less specific compared to analytical methods, bioluminescent bioassays are more cost-effective, more rapid, can be scaled to higher throughput, and can be designed to report not only the presence but also the bioavailability of target substances. This chapter reviews available bacterial and eukaryotic whole-cell bioreporters for sensing organic pollutants and their applications in a variety of sample matrices.
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Affiliation(s)
- Tingting Xu
- Joint Institute for Biological Sciences, The University of Tennessee, Knoxville, TN, USA
| | - Dan Close
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Abby Smartt
- Center for Environmental Biotechnology, The University of Tennessee, Knoxville, TN, USA; Department of Microbiology, The University of Tennessee, Knoxville, TN, USA
| | - Steven Ripp
- Center for Environmental Biotechnology, The University of Tennessee, Knoxville, TN, USADepartment of Microbiology, The University of Tennessee, Knoxville, TN, USA
| | - Gary Sayler
- Joint Institute for Biological Sciences, The University of Tennessee, Knoxville, TN, USA; Center for Environmental Biotechnology, The University of Tennessee, Knoxville, TN, USA; Department of Microbiology, The University of Tennessee, Knoxville, TN, USA
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Xu T, Close DM, Sayler GS, Ripp S. Genetically modified whole-cell bioreporters for environmental assessment. ECOLOGICAL INDICATORS 2013; 28:125-141. [PMID: 26594130 PMCID: PMC4649933 DOI: 10.1016/j.ecolind.2012.01.020] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Living whole-cell bioreporters serve as environmental biosentinels that survey their ecosystems for harmful pollutants and chemical toxicants, and in the process act as human and other higher animal proxies to pre-alert for unfavorable, damaging, or toxic conditions. Endowed with bioluminescent, fluorescent, or colorimetric signaling elements, bioreporters can provide a fast, easily measured link to chemical contaminant presence, bioavailability, and toxicity relative to a living system. Though well tested in the confines of the laboratory, real-world applications of bioreporters are limited. In this review, we will consider bioreporter technologies that have evolved from the laboratory towards true environmental applications, and discuss their merits as well as crucial advancements that still require adoption for more widespread utilization. Although the vast majority of environmental monitoring strategies rely upon bioreporters constructed from bacteria, we will also examine environmental biosensing through the use of less conventional eukaryotic-based bioreporters, whose chemical signaling capacity facilitates a more human-relevant link to toxicity and health-related consequences.
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Affiliation(s)
- Tingting Xu
- The University of Tennessee Center for Environmental Biotechnology, 676 Dabney Hall, Knoxville, TN 37996, USA
| | - Dan M. Close
- The Joint Institute for Biological Sciences, Oak Ridge National Laboratory, PO Box 2008, MS6342 Oak Ridge, TN 37831, USA
| | - Gary S. Sayler
- The University of Tennessee Center for Environmental Biotechnology, 676 Dabney Hall, Knoxville, TN 37996, USA
- The Joint Institute for Biological Sciences, Oak Ridge National Laboratory, PO Box 2008, MS6342 Oak Ridge, TN 37831, USA
| | - Steven Ripp
- The University of Tennessee Center for Environmental Biotechnology, 676 Dabney Hall, Knoxville, TN 37996, USA
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The evolution of the bacterial luciferase gene cassette (lux) as a real-time bioreporter. SENSORS 2012; 12:732-52. [PMID: 22368493 PMCID: PMC3279237 DOI: 10.3390/s120100732] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2011] [Revised: 12/30/2011] [Accepted: 01/09/2012] [Indexed: 01/23/2023]
Abstract
The bacterial luciferase gene cassette (lux) is unique among bioluminescent bioreporter systems due to its ability to synthesize and/or scavenge all of the substrate compounds required for its production of light. As a result, the lux system has the unique ability to autonomously produce a luminescent signal, either continuously or in response to the presence of a specific trigger, across a wide array of organismal hosts. While originally employed extensively as a bacterial bioreporter system for the detection of specific chemical signals in environmental samples, the use of lux as a bioreporter technology has continuously expanded over the last 30 years to include expression in eukaryotic cells such as Saccharomyces cerevisiae and even human cell lines as well. Under these conditions, the lux system has been developed for use as a biomedical detection tool for toxicity screening and visualization of tumors in small animal models. As the technologies for lux signal detection continue to improve, it is poised to become one of the first fully implantable detection systems for intra-organismal optical detection through direct marriage to an implantable photon-detecting digital chip. This review presents the basic biochemical background that allows the lux system to continuously autobioluminesce and highlights the important milestones in the use of lux-based bioreporters as they have evolved from chemical detection platforms in prokaryotic bacteria to rodent-based tumorigenesis study targets. In addition, the future of lux imaging using integrated circuit microluminometry to image directly within a living host in real-time will be introduced and its role in the development of dose/response therapeutic systems will be highlighted.
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Liu JB, Amemiya T, Chang Q, Xu X, Itoh K. Real-time reverse transcription PCR analysis of trichloroethylene-regulated toluene dioxygenase expression in Pseudomonas putida F1. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2011; 46:294-300. [PMID: 21500075 DOI: 10.1080/03601234.2011.559877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Toluene dioxygenase (tod) is a multicomponent enzyme system in Pseudomonas putida F1. Tod can mediate the degradation of Trichloroethylene (TCE), a widespread pollutant. In this study, we try to explore the TCE-regulated tod expression by using real-time qRT-PCR. The minimal culture media were supplemented with glucose, toluene, or a mixture of glucose/toluene respectively as carbon and energy sources. The TCE was injected into each medium after a 12-hour incubation period. The TCE injection severely affected bacterial growth when cultured with toluene or toluene/glucose mixtures. The cell density dropped 61 % for bacteria growing in toluene and 36 % for bacteria in the glucose/toluene mixture after TCE injection, but the TCE treatment had little effect on bacteria supplied with glucose alone. The decrease in cell number was caused by the cytotoxicity of the TCE metabolized by tod. The results from the real-time qRT-PCR revealed that TCE was capable of inducing tod expression in a toluene-dependent manner and that the tod expression level increased 50 times in toluene and 3 times in the toluene/glucose mixture after 6 hours of TCE treatment. Furthermore, validation of the rpoD gene as a reference gene for P. putida F1 was performed in this study, providing a valuable foundation for future studies to use real-time qRT-PCR in the analysis of the P. putida F1 strain.
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Affiliation(s)
- Jian B Liu
- Graduate School of Environment and Information Science, Yokohama National University, Yokohama, Japan.
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11
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Ju KS, Parales JV, Parales RE. Reconstructing the evolutionary history of nitrotoluene detection in the transcriptional regulator NtdR. Mol Microbiol 2009; 74:826-43. [PMID: 19849778 PMCID: PMC10423642 DOI: 10.1111/j.1365-2958.2009.06904.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many toxic man-made compounds have been introduced into the environment, and bacterial strains that are able to grow on them are ideal model systems for studying the evolution of metabolic pathways and regulatory systems. Acidovorax sp. strain JS42 is unique in its ability to use 2-nitrotoluene as a sole carbon, nitrogen, and energy source for growth. The LysR-type transcriptional regulator NtdR activates expression of the 2-nitrotoluene degradation genes not only when nitroaromatic compounds are present, but also in the presence of a wide range of aromatic acids and analogues. The molecular determinants of inducer specificity were identified through comparative analysis with NagR, the activator of the naphthalene degradation pathway genes in Ralstonia sp. strain U2. Although NagR is 98% identical to NtdR, it does not respond to nitrotoluenes. Exchange of residues that differ between NagR and NtdR revealed that residues at positions 227 and 232 were key for the recognition of nitroaromatic compounds, while the amino acid at position 169 determined the range of aromatic acids recognized. Structural modelling of NtdR suggests that these residues are near the predicted inducer binding pocket. Based on these results, an evolutionary model is presented that depicts the stepwise evolution of NtdR.
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Affiliation(s)
- Kou-San Ju
- Department of Microbiology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Juanito V. Parales
- Department of Microbiology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Rebecca E. Parales
- Department of Microbiology, College of Biological Sciences, University of California, Davis, CA 95616
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Use of gene probes to assess the impact and effectiveness of aerobic in situ bioremediation of TCE. Arch Microbiol 2008; 191:221-32. [DOI: 10.1007/s00203-008-0445-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 09/26/2008] [Accepted: 10/20/2008] [Indexed: 10/21/2022]
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Urgun-Demirtas M, Stark B, Pagilla K. Use of Genetically Engineered Microorganisms (GEMs) for the Bioremediation of Contaminants. Crit Rev Biotechnol 2008; 26:145-64. [PMID: 16923532 DOI: 10.1080/07388550600842794] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This paper presents a critical review of the literature on the application of genetically engineered microorganisms (GEMs) in bioremediation. The important aspects of using GEMs in bioremediation, such as development of novel strains with desirable properties through pathway construction and the modification of enzyme specificity and affinity, are discussed in detail. Particular attention is given to the genetic engineering of bacteria using bacterial hemoglobin (VHb) for the treatment of aromatic organic compounds under hypoxic conditions. The application of VHb technology may advance treatment of contaminated sites, where oxygen availability limits the growth of aerobic bioremediating bacteria, as well as the functioning of oxygenases required for mineralization of many organic pollutants. Despite the many advantages of GEMs, there are still concerns that their introduction into polluted sites to enhance bioremediation may have adverse environmental effects, such as gene transfer. The extent of horizontal gene transfer from GEMs in the environment, compared to that of native organisms including benefits regarding bacterial bioremediation that may occur as a result of such transfer, is discussed. Recent advances in tracking methods and containment strategies for GEMs, including several biological systems that have been developed to detect the fate of GEMs in the environment, are also summarized in this review. Critical research questions pertaining to the development and implementation of GEMs for enhanced bioremediation have been identified and posed for possible future research.
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Affiliation(s)
- Meltem Urgun-Demirtas
- Department of Chemical and Environmental Engineering, Illinois Institute of Technology, Chicago, 60616, USA
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Parales RE, Parales JV, Pelletier DA, Ditty JL. Diversity of microbial toluene degradation pathways. ADVANCES IN APPLIED MICROBIOLOGY 2008; 64:1-73, 2 p following 264. [PMID: 18485280 DOI: 10.1016/s0065-2164(08)00401-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- R E Parales
- Department of Microbiology, University of California, Davis, California 95616, USA
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Park MR, Banks MK, Applegate B, Webster TJ. Influence of nanophase titania topography on bacterial attachment and metabolism. Int J Nanomedicine 2008; 3:497-504. [PMID: 19337418 PMCID: PMC2636588 DOI: 10.2147/ijn.s4399] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Surfaces with nanophase compared to conventional (or nanometer smooth) topographies are known to have different properties of area, charge, and reactivity. Previously published research indicates that the attachment of certain bacteria (such as Pseudomonas fluorescens 5RL) is higher on surfaces with nanophase compared to conventional topographies, however, their effect on bacterial metabolism is unclear. Results presented here show that the adhesion of Pseudomonas fluorescens 5RL and Pseudomonas putida TVA8 was higher on nanophase than conventional titania. Importantly, in terms of metabolism, bacteria attached to the nanophase surfaces had higher bioluminescence rates than on the conventional surfaces under all nutrient conditions. Thus, the results from this study show greater select bacterial metabolism on nanometer than conventional topographies, critical results with strong consequences for the design of improved biosensors for bacteria detection.
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Affiliation(s)
| | | | | | - Thomas J Webster
- School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
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Dawson JJC, Iroegbu CO, Maciel H, Paton GI. Application of luminescent biosensors for monitoring the degradation and toxicity of BTEX compounds in soils. J Appl Microbiol 2007; 104:141-51. [PMID: 17922829 DOI: 10.1111/j.1365-2672.2007.03552.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To assess the changes in acute toxicity and biodegradation of benzene, toluene, ethylbenzene and xylene (collectively referred to as BTEX) compounds in soil over time and compare the performances of biological and chemical techniques. METHODS AND RESULTS Biological methods (lux-based bacterial biosensors, basal respiration and dehydrogenase activity) were related to changes in the concentration of the target compounds. There was an initial increase in toxicity determined by the constitutively expressed biosensor, followed by a continual reduction as degradation proceeded. The biosensor with the BTEX-specific promoter was most induced when BTEX concentrations were highest. The treatment with nutrient amendment had a significant increase in microbial activity, while the sterile control produced the lowest level of degradation. SIGNIFICANCE AND IMPACT OF THE STUDY Luminescent biosensors were able to monitor changes in contaminant toxicity and bioavailability in aqueous extracts from BTEX-impacted soils as degradation proceeded. The integration of biological tests with chemical analysis enables a fuller understanding of the biodegradation processes occurring at their relative rates. CONCLUSIONS The biological methods were successfully used in assessing the performance of different treatments for enhancing natural attenuation of BTEX from contaminated soils. While, chemical analysis showed biodegradation of parent BTEX compounds in biologically active soils, the biosensor assays reported on changes in bioavailability and potentially toxic intermediate fractions as they estimated the integrative effect of contaminants.
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Affiliation(s)
- J J C Dawson
- School of Biological Sciences, University of Aberdeen, Aberdeen, UK.
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17
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Doughty DM, Sayavedra-Soto LA, Arp DJ, Bottomley PJ. Effects of dichloroethene isomers on the induction and activity of butane monooxygenase in the alkane-oxidizing bacterium "Pseudomonas butanovora". Appl Environ Microbiol 2005; 71:6054-9. [PMID: 16204521 PMCID: PMC1265974 DOI: 10.1128/aem.71.10.6054-6059.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We examined cooxidation of three different dichloroethenes (1,1-DCE, 1,2-trans DCE, and 1,2-cis DCE) by butane monooxygenase (BMO) in the butane-utilizing bacterium "Pseudomonas butanovora." Different organic acids were tested as exogenous reductant sources for this process. In addition, we determined if DCEs could serve as surrogate inducers of BMO gene expression. Lactic acid supported greater rates of oxidation of the three DCEs than the other organic acids tested. The impacts of lactic acid-supported DCE oxidation on BMO activity differed among the isomers. In intact cells, 50% of BMO activity was irreversibly lost after consumption of approximately 20 nmol mg protein(-1) of 1,1-DCE and 1,2-trans DCE in 0.5 and 5 min, respectively. In contrast, a comparable loss of activity required the oxidation of 120 nmol 1,2-cis DCE mg protein(-1). Oxidation of similar amounts of each DCE isomer ( approximately 20 nmol mg protein(-1)) produced different negative effects on lactic acid-dependent respiration. Despite 1,1-DCE being consumed 10 times faster than 1,2,-trans DCE, respiration declined at similar rates, suggesting that the product(s) of oxidation of 1,2-trans DCE was more toxic to respiration than 1,1-DCE. Lactate-grown "P. butanovora" did not express BMO activity but gained activity after exposure to butane, ethene, 1,2-cis DCE, or 1,2-trans DCE. The products of BMO activity, ethene oxide and 1-butanol, induced lacZ in a reporter strain containing lacZ fused to the BMO promoter, whereas butane, ethene, and 1,2-cis DCE did not. 1,2-trans DCE was unique among the BMO substrates tested in its ability to induce lacZ expression.
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Affiliation(s)
- D M Doughty
- Dept. of Microbiology, Nash Hall Rm. 220, Oregon State University, Corvallis, OR 97331-3804, USA
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Bhattacharyya J, Read D, Amos S, Dooley S, Killham K, Paton GI. Biosensor-based diagnostics of contaminated groundwater: assessment and remediation strategy. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2005; 134:485-492. [PMID: 15620594 DOI: 10.1016/j.envpol.2004.09.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 09/08/2004] [Indexed: 05/24/2023]
Abstract
Shallow groundwater beneath a former airfield site in southern England has been heavily contaminated with a wide range of chlorinated solvents. The feasibility of using bacterial biosensors to complement chemical analysis and enable cost-effective, and focussed sampling has been assessed as part of a site evaluation programme. Five different biosensors, three metabolic (Vibrio fischeri, Pseudomonas fluorescens 10568 and Escherichia coli HB101) and two catabolic (Pseudomonas putida TVA8 and E. coli DH5alpha), were employed to identify areas where the availability and toxicity of pollutants is of most immediate environmental concern. The biosensors used showed different sensitivities to each other and to the groundwater samples tested. There was generally a good agreement with chemical analyses. The potential efficacy of remediation strategies was explored by coupling sample manipulation to biosensor tests. Manipulation involved sparging and charcoal treatment procedures to simulate remediative engineering solutions. Sparging was sufficient at most locations.
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Affiliation(s)
- Jessica Bhattacharyya
- University of Aberdeen, School of Biological Sciences, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UK
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19
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Johnson EL, Smith CA, O'Reilly KT, Hyman MR. Induction of methyl tertiary butyl ether (MTBE)-oxidizing activity in Mycobacterium vaccae JOB5 by MTBE. Appl Environ Microbiol 2004; 70:1023-30. [PMID: 14766585 PMCID: PMC348811 DOI: 10.1128/aem.70.2.1023-1030.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alkane-grown cells of Mycobacterium vaccae JOB5 cometabolically degrade the gasoline oxygenate methyl tertiary butyl ether (MTBE) through the activities of an alkane-inducible monooxygenase and other enzymes in the alkane oxidation pathway. In this study we examined the effects of MTBE on the MTBE-oxidizing activity of M. vaccae JOB5 grown on diverse nonalkane substrates. Carbon-limited cultures were grown on glycerol, lactate, several sugars, and tricarboxylic acid cycle intermediates, both in the presence and absence of MTBE. In all MTBE-containing cultures, MTBE consumption occurred and tertiary butyl alcohol (TBA) and tertiary butyl formate accumulated in the culture medium. Acetylene, a specific inactivator of alkane- and MTBE-oxidizing activities, fully inhibited MTBE consumption and product accumulation but had no other apparent effects on culture growth. The MTBE-dependent stimulation of MTBE-oxidizing activity in fructose- and glycerol-grown cells was saturable with respect to MTBE concentration (50% saturation level = 2.4 to 2.75 mM), and the onset of MTBE oxidation in glycerol-grown cells was inhibited by both rifampin and chloramphenicol. Other oxygenates (TBA and tertiary amyl methyl ether) also induced the enzyme activity required for their own degradation in glycerol-grown cells. Presence of MTBE also promoted MTBE oxidation in cells grown on organic acids, compounds that are often found in anaerobic, gasoline-contaminated environments. Experiments with acid-grown cells suggested induction of MTBE-oxidizing activity by MTBE is subject to catabolite repression. The results of this study are discussed in terms of their potential implications towards our understanding of the role of cometabolism in MTBE and TBA biodegradation in gasoline-contaminated environments.
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Affiliation(s)
- Erika L Johnson
- Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695, USA
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20
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Phoenix P, Keane A, Patel A, Bergeron H, Ghoshal S, Lau PCK. Characterization of a new solvent-responsive gene locus in Pseudomonas putida F1 and its functionalization as a versatile biosensor. Environ Microbiol 2004; 5:1309-27. [PMID: 14641576 DOI: 10.1111/j.1462-2920.2003.00426.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A new gene cluster, designated sepABC and a divergently transcribed sepR, was found downstream of the two-component todST phosphorelay system that regulates toluene degradation (the tod pathway) in Pseudomonas putida F1 (PpF1). The deduced amino acid sequences encoded by sepABC show a high homology to bacterial proteins known to be involved in solvent efflux or multidrug pumps. SepA, SepB and SepC are referred to be periplasmic, inner membrane and outer membrane efflux proteins respectively. Effects on growth of various PpF1 mutants compared to that of the wild type in the presence of toluene indicated a possible protective role of the solvent efflux system in a solvent-stressed environment. Growth tests with the complemented mutants confirmed the involvement of the Sep proteins in conferring solvent tolerance. The sepR gene encodes a 260-residue polypeptide that is a member of the E. coli IclR repressor protein family. The repressor role of SepR was established by conducting tests with a sep-lacZ transcriptional fusion in Escherichia coli and PpF1, expression of SepR as a maltose-binding fusion protein in a DNA binding assay, and mRNA analysis. Southern hybridization experiments and analysis of the P. putida KT2440 genome sequence indicated that sepR is a relatively rare commodity compared to homologues of the sepABC genes. We developed a whole-cell bioluminescent biosensor, PpF1G4, which contains a chromosomally based sep-lux transcriptional fusion. The biosensor showed significant induction of the sepABC genes by a wide variety of aromatic molecules, including benzene, toluene, ethylbenzene, and all three isomers of xylene (BTEX), naphthalene, and complex mixtures of aliphatic and aromatic hydrocarbons. PpF1G4 represents a second-generation biosensor that is not based on a catabolic promoter but is nonetheless inducible by aromatic pollutants and moreover functional under nutrient-rich conditions.
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MESH Headings
- Bacterial Proteins/chemistry
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Base Sequence
- Biosensing Techniques
- DNA, Bacterial/chemistry
- DNA, Bacterial/isolation & purification
- Environmental Pollutants/analysis
- Environmental Pollutants/metabolism
- Gene Deletion
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Genes, Reporter
- Genetic Complementation Test
- Hydrocarbons, Aromatic/analysis
- Hydrocarbons, Aromatic/metabolism
- Hydrocarbons, Aromatic/pharmacology
- Lac Operon
- Luminescent Measurements
- Membrane Transport Proteins/genetics
- Membrane Transport Proteins/metabolism
- Molecular Sequence Data
- Promoter Regions, Genetic
- Pseudomonas putida/genetics
- Pseudomonas putida/metabolism
- Repressor Proteins/genetics
- Repressor Proteins/metabolism
- Sequence Analysis, DNA
- Sequence Homology
- Solvents/analysis
- Solvents/metabolism
- Solvents/pharmacology
- Toluene/metabolism
- Toluene/pharmacology
- beta-Galactosidase/metabolism
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Affiliation(s)
- P Phoenix
- Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Ave., Montreal, Quebec, Canada H4P 2R2
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21
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Nivens DE, McKnight TE, Moser SA, Osbourn SJ, Simpson ML, Sayler GS. Bioluminescent bioreporter integrated circuits: potentially small, rugged and inexpensive whole-cell biosensors for remote environmental monitoring. J Appl Microbiol 2004; 96:33-46. [PMID: 14678157 DOI: 10.1046/j.1365-2672.2003.02114.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- D E Nivens
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN 37996, USA
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22
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Park J, Kukor JJ, Abriola LM. Characterization of the adaptive response to trichloroethylene-mediated stresses in Ralstonia pickettii PKO1. Appl Environ Microbiol 2002; 68:5231-40. [PMID: 12406709 PMCID: PMC129943 DOI: 10.1128/aem.68.11.5231-5240.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Ralstonia pickettii PKO1, a denitrifying toluene oxidizer that carries a toluene-3-monooxygenase (T3MO) pathway, the biodegradation of toluene and trichloroethylene (TCE) by the organism is induced by TCE at high concentrations. In this study, the effect of TCE preexposure was studied in the context of bacterial protective response to TCE-mediated toxicity in this organism. The results of TCE degradation experiments showed that cells induced by TCE at 110 mg/liter were more tolerant to TCE-mediated stress than were those induced by TCE at lower concentrations, indicating an ability of PKO1 to adapt to TCE-mediated stress. To characterize the bacterial protective response to TCE-mediated stress, the effect of TCE itself (solvent stress) was isolated from TCE degradation-dependent stress (toxic intermediate stress) in the subsequent chlorinated ethylene toxicity assays with both nondegradable tetrachloroethylene and degradable TCE. The results of the toxicity assays showed that TCE preexposure led to an increase in tolerance to TCE degradation-dependent stress rather than to solvent stress. The possibility that such tolerance was selected by TCE degradation-dependent stress during TCE preexposure was ruled out because a similar extent of tolerance was observed in cells that were induced by toluene, whose metabolism does not produce any toxic products. These findings suggest that the adaptation of TCE-induced cells to TCE degradation-dependent stress was caused by the combined effects of solvent stress response and T3MO pathway expression.
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Affiliation(s)
- Joonhong Park
- Center for Microbial Ecology, Michigan State University, East Lansing, Michigan 48824-1325, USA
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23
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Stiner L, Halverson LJ. Development and characterization of a green fluorescent protein-based bacterial biosensor for bioavailable toluene and related compounds. Appl Environ Microbiol 2002; 68:1962-71. [PMID: 11916719 PMCID: PMC123894 DOI: 10.1128/aem.68.4.1962-1971.2002] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A green fluorescent protein-based Pseudomonas fluorescens strain A506 biosensor was constructed and characterized for its potential to measure benzene, toluene, ethylbenzene, and related compounds in aqueous solutions. The biosensor is based on a plasmid carrying the toluene-benzene utilization (tbu) pathway transcriptional activator TbuT from Ralstonia pickettii PKO1 and a transcriptional fusion of its promoter PtbuA1 with a promoterless gfp gene on a broad-host-range promoter probe vector. TbuT was not limiting, since it was constitutively expressed by being fused to the neomycin phosphotransferase (nptII) promoter. The biosensor cells were readily induced, and fluorescence emission after induction periods of 3 h correlated well with toluene, benzene, ethylbenzene, and trichloroethylene concentrations. Our experiments using flow cytometry show that intermediate levels of gfp expression in response to toluene reflect uniform induction of cells. As the toluene concentration increases, the level of gfp expression per cell increases until saturation kinetics of the TbuT-PtbuA1 system are observed. Each inducer had a unique minimum concentration that was necessary for induction, with K(app) values that ranged from 3.3 +/- 1.8 microM for toluene to 35.6 +/- 16.6 microM for trichloroethylene (means +/- standard errors of the means), and maximal fluorescence response. The fluorescence response was specific for alkyl-substituted benzene derivatives and branched alkenes (di- and trichloroethylene, 2-methyl-2-butene). The biosensor responded in an additive fashion to the presence of multiple inducers and was unaffected by the presence of compounds that were not inducers, such as those present in gasoline. Flow cytometry revealed that, in response to toxic concentrations of gasoline, there was a small uninduced population and another larger fully induced population whose levels of fluorescence corresponded to the amount of effectors present in the sample. These results demonstrate the potential for green fluorescent protein-based bacterial biosensors to measure environmental contaminants.
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Affiliation(s)
- Lawrence Stiner
- Department of Microbiology, Iowa State University, Ames, Iowa 50011-1010, USA
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24
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Abstract
There is a continuing need for monitoring the health of the environment due to the presence of pollutants. Here, we review the development and attributes of biosensors by which bacteria have been genetically modified to express the luminescence genes, i.e. to glow, in a quantified manner, in response to pollutants. We have concentrated on the detection of organic hydrocarbon pollutants and discussed the molecular mechanisms by which some of these chemicals act as effector molecules on the respective regulatory systems. The future of environmental biosensors is predictably bright. As more knowledge is gathered on the sensing regulatory component, the possibility of developing targeted or pollutant-specific biosensors is promising. Moreover, the repertoire of biosensors for culprit organic pollutants is expected to be enlarged through advances in genomics technology and identification of new sensory or receptor molecules. The need for pollutant detection at concentrations in the parts per trillion range or biosensors configured in a nanoscale is anticipated.
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Affiliation(s)
- Angela Keane
- Department of Civil Engineering and Applied Mechanics, McGill University, Montreal, Quebec, Canada
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25
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Park J, Chen YM, Kukor JJ, Abriola LM. Influence of substrate exposure history on biodegradation in a porous medium. JOURNAL OF CONTAMINANT HYDROLOGY 2001; 51:233-256. [PMID: 11588828 DOI: 10.1016/s0169-7722(01)00125-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This study investigates the influence of fluctuating toluene concentrations on aerobic toluene degradation in a sandy porous medium colonized with Ralstonia pickettii PKO1. Column effluent toluene concentrations were found to increase after a temporary decrease in influent toluene concentration. Subsequent examination of the spatial gradient of toluene degradative activity in the column suggested that the observed increase in effluent toluene concentrations was attributable to an adverse effect of toluene limitation on the biodegradative activity of attached cells. The traditional Michaelis-Menten-type biodegradation equation associated with batch-measured Vmax (2.26 mg toluene/mg living cell/day) and KS (1.20 mg toluene/1) of nonstarved cells was unable to predict the observed toluene breakthrough behavior when the column had been previously exposed to no-toluene conditions. An alternative modeling approach was developed based upon the assumptions that (i) degradative activity was completely deactivated within the no-toluene exposure period (53.5 h) and (ii) a lag-phase was present prior to the subsequent reactivation of degradative activity in previously toluene-starved cells. These assumptions were independently verified by batch microbial investigations, and the modified model provided a good fit to the same observed toluene breakthrough curve. Application of single lag-time and threshold concentration values, however, failed to predict observed toluene breakthrough under different toluene exposure conditions. Results of this experimental and modeling investigation suggested that substrate exposure history, including the length of the starvation period and the level of substrate concentration, affected the induction of biodegradation in the porous medium.
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Affiliation(s)
- J Park
- Environmental and Water Resources Engineering, University of Michigan, 181 EWRE Building, 1351 Beal Avenue, Ann Arbor, MI 48109-2125, USA
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26
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Sayler GS, Fleming JT, Nivens DE. Gene expression monitoring in soils by mRNA analysis and gene lux fusions. Curr Opin Biotechnol 2001; 12:455-60. [PMID: 11604320 DOI: 10.1016/s0958-1669(00)00245-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two methods recently developed to monitor the gene expression of microbial communities in soil are the extraction and detection of messenger RNA from soil microorganisms and the construction and use of lux-based bioreporter strains. The goal of these approaches is to assess microbial activity in natural and impacted soil environments.
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Affiliation(s)
- G S Sayler
- Department of Microbiology, University of Tennessee, 676 Dabney Hall, Knoxville TN 37996-1605, USA.
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27
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Abstract
The ability to manipulate systems on the molecular scale naturally leads to speculation about the rational design of molecular-scale machines. Cells might be the ultimate molecular-scale machines and our ability to engineer them is relatively advanced when compared with our ability to control the synthesis and direct the assembly of man-made materials. Indeed, engineered whole cells deployed in biosensors can be considered one of the practical successes of molecular-scale devices. However, these devices explore only a small portion of cellular functionality. Individual cells or self-organized groups of cells perform extremely complex functions that include sensing, communication, navigation, cooperation and even fabrication of synthetic nanoscopic materials. In natural systems, these capabilities are controlled by complex genetic regulatory circuits, which are only partially understood and not readily accessible for use in engineered systems. Here, we focus on efforts to mimic the functionality of man-made information-processing systems within whole cells.
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Affiliation(s)
- M L Simpson
- The Oak Ridge National Laboratory, PO Box 2008, MS 6006, Oak Ridge, TN 37831-6006, USA. icsun1.cornl.gov
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28
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Roda A, Pasini P, Mirasoli M, Guardigli M, Russo C, Musiani M, Baraldini M. SENSITIVE DETERMINATION OF URINARY MERCURY(II) BY A BIOLUMINESCENT TRANSGENIC BACTERIA-BASED BIOSENSOR. ANAL LETT 2001. [DOI: 10.1081/al-100002702] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Abstract
Unraveling the complex transcriptional regulation of bacterial catabolism of aromatic pollutants is a prerequisite for engineering efficient biological systems for many biotechnological applications. A first level of regulation relies on specific regulator-promoter pairs. There have been new insights into the molecular mechanisms that regulatory proteins use to sense a given signal and to activate transcription initiation from the cognate promoters. A second level of regulation allows adjustment of the expression of the particular catabolic operons in response to the global environmental conditions of the cells, and recent findings provide some clues about the mechanisms underlying such complex regulatory checkpoints.
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Affiliation(s)
- E Díaz
- Department of Molecular Microbiology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Velázquez 144, 28006, Madrid, Spain.
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30
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Kelly CJ, Bienkowski PR, Sayler GS. Kinetic analysis of a tod-lux bacterial reporter for toluene degradation and trichloroethylene cometabolism. Biotechnol Bioeng 2000; 69:256-65. [PMID: 10861405 DOI: 10.1002/1097-0290(20000805)69:3<256::aid-bit3>3.0.co;2-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Kinetics of toluene and trichloroethylene (TCE) degradation and bioluminescence from the bioreporter Pseudomonas putida B2 and TVA8 were investigated utilizing batch and continuous culture, respectively. Degradation was modeled using a Michaelis-Menten expression for the competition of two substrates for a single enzyme system, and bioluminescence was modeled assuming a luciferase enzyme saturational dependence on toluene as the inducer and growth substrate. During the batch experiments, bioluminescence increased at approximately 90 namp/min for initial toluene concentrations of 10 to 50 mg/L, but more slowly at higher toluene concentrations, suggesting maximum promoter induction at below 10 mg/L and toxic effects above 50 mg/L toluene. TCE degradation did not occur until toluene depletion, presumably due to competition between toluene and TCE for the toluene dioxygenase enzyme. During continuous culture, bioluminescence transiently increased, then gradually decreased in response to increasing step changes in toluene feed concentration. Bioluminescence in the CSTR appeared to be limited by growth substrate and/or inducer.
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Affiliation(s)
- C J Kelly
- Department of Chemical Engineering and Materials Science, Syracuse University, New York 13244-1190, USA
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31
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Ryoo D, Shim H, Canada K, Barbieri P, Wood TK. Aerobic degradation of tetrachloroethylene by toluene-o-xylene monooxygenase of Pseudomonas stutzeri OX1. Nat Biotechnol 2000; 18:775-8. [PMID: 10888848 DOI: 10.1038/77344] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tetrachloroethylene (PCE) is thought to have no natural source, so it is one of the most difficult contaminants to degrade biologically. This common groundwater pollutant was thought completely nonbiodegradable in the presence of oxygen. Here we report that the wastewater bacterium Pseudomonas stutzeri OX1 degrades aerobically 0. 56 micromol of 2.0 micromol PCE in 21 h (Vmax approximately 2.5 nmol min(-1) mg(-1) protein and KM approximately 34 microM). These results were corroborated by the generation of 0.48 micromol of the degradation product, chloride ions. This degradation was confirmed to be a result of expression of toluene-o-xylene monooxygenase (ToMO) by P. stutzeri OX1, since cloning and expressing this enzyme in Escherichia coli led to the aerobic degradation of 0.19 micromol of 2.0 micromol PCE and the generation of stoichiometric amounts of chloride. In addition, PCE induces formation of ToMO, which leads to its own degradation in P. stutzeri OX1. Degradation intermediates reduce the growth rate of this strain by 27%.
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Affiliation(s)
- D Ryoo
- Department of Chemical Engineering, University of Connecticut, Storrs, CT 06269-3222, USA
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