1
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Ciemniecki JA, Newman DK. NADH dehydrogenases are the predominant phenazine reductases in the electron transport chain of Pseudomonas aeruginosa. Mol Microbiol 2023; 119:560-573. [PMID: 36840394 PMCID: PMC11129870 DOI: 10.1111/mmi.15049] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 02/15/2023] [Accepted: 02/21/2023] [Indexed: 02/26/2023]
Abstract
Phenazines are redox-active secondary metabolites produced by diverse bacteria including the opportunistic pathogen Pseudomonas aeruginosa. Extracellular electron transfer via phenazines enhances anaerobic survival by serving as an electron sink for glucose catabolism. However, the specific phenazine reductase(s) used to support this catabolism are unknown. Because electron transport chain components have been previously implicated in phenazine reduction, we sought to determine which of them possess phenazine reductase activity. We show that phenazine-1-carboxamide (PCN) and pyocyanin (PYO) are reduced at the highest rate by cells and are localized to the cell envelope while reduced. Using a coupled genetic and biochemical approach, we show that phenazine reductase activity in membrane fractions is attributable to the three NADH dehydrogenases present in P. aeruginosa and that their order of phenazine reductase activity is Nqr > Nuo > Ndh. In mutants possessing only one functional NADH dehydrogenase, whole cell reduction rates of PCN, but not PYO, recapitulate the pattern of biochemical results, implying that PYO reduction is predominantly occurring in the cytosol. Lastly, we show that ubiquinone rapidly and non-enzymatically oxidizes reduced phenazines, demonstrating that phenazines have the capability to serve in a redox loop between the NADH and ubiquinone pools, a finding that carries bioenergetic implications.
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Affiliation(s)
- John A Ciemniecki
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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2
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McRose D, Li J, Newman D. The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads. Proc Natl Acad Sci U S A 2023; 120:e2217951120. [PMID: 36996105 PMCID: PMC10083548 DOI: 10.1073/pnas.2217951120] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 02/27/2023] [Indexed: 03/31/2023] Open
Abstract
Secondary metabolites are important facilitators of plant-microbe interactions in the rhizosphere, contributing to communication, competition, and nutrient acquisition. However, at first glance, the rhizosphere seems full of metabolites with overlapping functions, and we have a limited understanding of basic principles governing metabolite use. Increasing access to the essential nutrient iron is one important, but seemingly redundant role performed by both plant and microbial Redox-Active Metabolites (RAMs). We used coumarins, RAMs made by the model plant Arabidopsis thaliana, and phenazines, RAMs made by soil-dwelling pseudomonads, to ask whether plant and microbial RAMs might each have distinct functions under different environmental conditions. We show that variations in oxygen and pH lead to predictable differences in the capacity of coumarins vs phenazines to increase the growth of iron-limited pseudomonads and that these effects depend on whether pseudomonads are grown on glucose, succinate, or pyruvate: carbon sources commonly found in root exudates. Our results are explained by the chemical reactivities of these metabolites and the redox state of phenazines as altered by microbial metabolism. This work shows that variations in the chemical microenvironment can profoundly affect secondary metabolite function and suggests plants may tune the utility of microbial secondary metabolites by altering the carbon released in root exudates. Together, these findings suggest that RAM diversity may be less overwhelming when viewed through a chemical ecological lens: Distinct molecules can be expected to be more or less important to certain ecosystem functions, such as iron acquisition, depending on the local chemical microenvironments in which they reside.
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Affiliation(s)
- Darcy L. McRose
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA91125
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA91125
| | - Jinyang Li
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA91125
| | - Dianne K. Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA91125
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA91125
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3
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Network-Based Redox Communication Between Abiotic Interactive Materials. iScience 2022; 25:104548. [PMID: 35747390 PMCID: PMC9209720 DOI: 10.1016/j.isci.2022.104548] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 04/28/2022] [Accepted: 06/02/2022] [Indexed: 11/29/2022] Open
Abstract
Recent observations that abiotic materials can engage in redox-based interactive communication motivates the search for new redox-active materials. Here we fabricated a hydrogel from a four-armed thiolated polyethylene glycol (PEG-SH) and the bacterial metabolite, pyocyanin (PYO). We show that: (i) the PYO-PEG hydrogel is reversibly redox-active; (ii) the molecular-switching and directed electron flow within this PYO-PEG hydrogel requires both a thermodynamic driving force (i.e., potential difference) and diffusible electron carriers that serve as nodes in a redox network; (iii) this redox-switching and electron flow is controlled by the redox network’s topology; and (iv) the ability of the PYO-PEG hydrogel to “transmit” electrons to a second insoluble redox-active material (i.e., a catechol-PEG hydrogel) is context-dependent (i.e., dependent on thermodynamic driving forces and appropriate redox shuttles). These studies provide an experimental demonstration of important features of redox-communication and also suggest technological opportunities for the fabrication of interactive materials. Thiol-pyocyanin reaction was used to create a redox-active and interactive hydrogel The electron flow and molecular switching requires diffusible mediators These mediators and pyocyanin hydrogel serve as “nodes” in a redox reaction network The networked flow of electrons between two separated hydrogels is reported
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4
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Nitrate Reduction Stimulates and Is Stimulated by Phenazine-1-Carboxylic Acid Oxidation by Citrobacter portucalensis MBL. mBio 2021; 12:e0226521. [PMID: 34465028 PMCID: PMC8437036 DOI: 10.1128/mbio.02265-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Phenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate. When C. portucalensis MBL is provided reduced PCA and nitrate, it oxidizes the PCA at a rate that is environmentally relevant. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other gammaproteobacteria with various capacities to respire nitrate. We found that PCA oxidation by these strains in a nitrate-dependent manner is decoupled from growth and strain dependent. We infer that bacterial PCA oxidation is widespread and genetically determined. Notably, oxidizing PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric exchange of electrons from PCA to nitrate, which we attribute to C. portucalensis MBL’s ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent.
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5
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McRose DL, Newman DK. Redox-active antibiotics enhance phosphorus bioavailability. Science 2021; 371:1033-1037. [PMID: 33674490 DOI: 10.1126/science.abd1515] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 01/13/2021] [Indexed: 12/13/2022]
Abstract
Microbial production of antibiotics is common, but our understanding of their roles in the environment is limited. In this study, we explore long-standing observations that microbes increase the production of redox-active antibiotics under phosphorus limitation. The availability of phosphorus, a nutrient required by all life on Earth and essential for agriculture, can be controlled by adsorption to and release from iron minerals by means of redox cycling. Using phenazine antibiotic production by pseudomonads as a case study, we show that phenazines are regulated by phosphorus, solubilize phosphorus through reductive dissolution of iron oxides in the lab and field, and increase phosphorus-limited microbial growth. Phenazines are just one of many examples of phosphorus-regulated antibiotics. Our work suggests a widespread but previously unappreciated role for redox-active antibiotics in phosphorus acquisition and cycling.
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Affiliation(s)
- Darcy L McRose
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. .,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
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6
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Zhang Y, Krahnert I, Bolze A, Gibon Y, Fernie AR. Adenine Nucleotide and Nicotinamide Adenine Dinucleotide Measurements in Plants. ACTA ACUST UNITED AC 2020; 5:e20115. [PMID: 32841544 DOI: 10.1002/cppb.20115] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
As the principal co-factors of many metabolic pathways, the measurement of both adenine nucleotides and nicotinamide adenine dinucleotide provides important information about cellular energy metabolism. However, given their rapid and reversible conversion as well as their relatively low concentration ranges, it is difficult to measure these compounds. Here, we describe a highly sensitive and selective ion-pairing HPLC method with fluorescence detection to quantify adenine nucleotides in plants. In addition, nicotinamide adenine dinucleotide is a crucially important redox-active substrate for multiple catabolic and anabolic reactions with the ratios of NAD+ /NADH and NADP+ /NADPH being suggested as indicators of the general intracellular redox potential and hence metabolic state. Here, we describe highly sensitive enzyme cycling-based colorimetric assays (with a detection limit in the pmol range) performed subsequent to a simple extraction procedure involving acid or base extraction to allow the measurement of the cellular levels of these metabolites. © 2020 The Authors. Basic Protocol 1: Preparation of plant material for the measurement Basic Protocol 2: Measurement of ATP, ADP, and AMP via HPLC Basic Protocol 3: NAD+ /NADP+ measurements Basic Protocol 4: NADH/NADPH measurements Basic Protocol 5: Data analysis and quality control approaches.
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Affiliation(s)
- Youjun Zhang
- Center of Plant Systems Biology and Biotechnology, Plovdiv, Bulgaria.,Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Ina Krahnert
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Antje Bolze
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Yves Gibon
- Institut National de la Recherche Agronomique (INRAE), University of Bordeaux, Villenave d'Ornon, France
| | - Alisdair R Fernie
- Center of Plant Systems Biology and Biotechnology, Plovdiv, Bulgaria.,Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
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7
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Warncke P, Fink S, Wiegand C, Hipler UC, Fischer D. A shell-less hen's egg test as infection model to determine the biocompatibility and antimicrobial efficacy of drugs and drug formulations against Pseudomonas aeruginosa. Int J Pharm 2020; 585:119557. [PMID: 32565284 DOI: 10.1016/j.ijpharm.2020.119557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 06/12/2020] [Accepted: 06/14/2020] [Indexed: 12/20/2022]
Abstract
A shell-less hen's egg based infection test with Pseudomonas aeruginosa was established to investigate the antimicrobial efficacy of drugs and drug formulations close to the in vivo situation. The test system using preincubated fertilized chicken eggs transferred in petri dishes was optimized with respect to the controlled local application of liquid materials and bacteria as well as the bacterial cultivation conditions. The applicability of the ex ovo infection model was confirmed with antimicrobial susceptibility tests using tobramycin, ciprofloxacin and meropenem. The validity of the ex ovo data was demonstrated by correlation with in vitro data of the CellTiter®-Blue and the microplate laser nephelometry assay. Real-time imaging of the progress of infection and the efficacy of the treatment could be realized by the MolecuLight i:X™ technique. Furthermore, in a proof-of-concept efficacy, biocompatibility and even the presence of irritants were determined side-by-side using commercial ophthalmics. In conclusion, this egg based infection model could bridge the gap between in vitro and in vivo models for the evaluation of antimicrobial susceptibility to reduce animal tests according to the 3R concept.
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Affiliation(s)
- Paul Warncke
- Pharmaceutical Technology and Biopharmacy, Friedrich-Schiller-University Jena, Lessingstraße 8, 07743 Jena, Germany
| | - Sarah Fink
- Department of Dermatology, University Medical Center Jena, Erfurter Str 35, 07740 Jena, Germany
| | - Cornelia Wiegand
- Department of Dermatology, University Medical Center Jena, Erfurter Str 35, 07740 Jena, Germany
| | - Uta-Christina Hipler
- Department of Dermatology, University Medical Center Jena, Erfurter Str 35, 07740 Jena, Germany
| | - Dagmar Fischer
- Pharmaceutical Technology and Biopharmacy, Friedrich-Schiller-University Jena, Lessingstraße 8, 07743 Jena, Germany; Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena, Humboldtstraße 10, 07743 Jena, Germany.
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8
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Simoska O, Sans M, Eberlin LS, Shear JB, Stevenson KJ. Electrochemical monitoring of the impact of polymicrobial infections on Pseudomonas aeruginosa and growth dependent medium. Biosens Bioelectron 2019; 142:111538. [DOI: 10.1016/j.bios.2019.111538] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/16/2019] [Accepted: 07/24/2019] [Indexed: 01/04/2023]
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9
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Rennie MY, Dunham D, Lindvere-Teene L, Raizman R, Hill R, Linden R. Understanding Real-Time Fluorescence Signals from Bacteria and Wound Tissues Observed with the MolecuLight i:X TM. Diagnostics (Basel) 2019; 9:E22. [PMID: 30813551 PMCID: PMC6468690 DOI: 10.3390/diagnostics9010022] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 02/20/2019] [Accepted: 02/20/2019] [Indexed: 11/16/2022] Open
Abstract
The persistent presence of pathogenic bacteria is one of the main obstacles to wound healing. Detection of wound bacteria relies on sampling methods, which delay confirmation by several days. However, a novel handheld fluorescence imaging device has recently enabled real-time detection of bacteria in wounds based on their intrinsic fluorescence characteristics, which differ from those of background tissues. This device illuminates the wound with violet (405 nm) light, causing tissues and bacteria to produce endogenous, characteristic fluorescence signals that are filtered and displayed on the device screen in real-time. The resulting images allow for rapid assessment and documentation of the presence, location, and extent of fluorescent bacteria at moderate-to-heavy loads. This information has been shown to assist in wound assessment and guide patient-specific treatment plans. However, proper image interpretation is essential to assessing this information. To properly identify regions of bacterial fluorescence, users must understand: (1) Fluorescence signals from tissues (e.g., wound tissues, tendon, bone) and fluids (e.g., blood, pus); (2) fluorescence signals from bacteria (red or cyan); (3) the rationale for varying hues of both tissue and bacterial fluorescence; (4) image artifacts that can occur; and (5) some potentially confounding signals from non-biological materials (e.g., fluorescent cleansing solutions). Therefore, this tutorial provides clinicians with a rationale for identifying common wound fluorescence characteristics. Clinical examples are intended to help clinicians with image interpretation-with a focus on image artifacts and potential confounders of image interpretation-and suggestions of how to overcome such challenges when imaging wounds in clinical practice.
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Affiliation(s)
| | | | | | - Rose Raizman
- Department of Professional Practice, Scarborough and Rouge Hospital, Toronto, ON M1E 4B9, Canada.
| | - Rosemary Hill
- Department of Ambulatory Care, Lions Gate Hospital, Vancouver Coastal Health, North Vancouver, BC V7L 2L7, Canada.
| | - Ron Linden
- Judy Dan Research and Treatment Centre, North York, ON M2R 1N5, Canada.
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10
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Simoska O, Sans M, Fitzpatrick MD, Crittenden CM, Eberlin LS, Shear JB, Stevenson KJ. Real-Time Electrochemical Detection of Pseudomonas aeruginosa Phenazine Metabolites Using Transparent Carbon Ultramicroelectrode Arrays. ACS Sens 2019; 4:170-179. [PMID: 30525472 DOI: 10.1021/acssensors.8b01152] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Here, we use a recently developed electrochemical sensing platform of transparent carbon ultramicroelectrode arrays (T-CUAs) for the in vitro detection of phenazine metabolites from the opportunistic human pathogen Pseudomonas aeruginosa. Specifically, redox-active metabolites pyocyanin (PYO), 5-methylphenazine-1-carboxylic acid (5-MCA), and 1-hydroxyphenazine (OHPHZ) are produced by P. aeruginosa, which is commonly found in chronic wound infections and in the lungs of cystic fibrosis patients. As highly diffusible chemicals, PYO and other metabolites are extremely toxic to surrounding host cells and other competing microorganisms, thus their detection is of great importance as it could provide insights regarding P. aeruginosa virulence mechanisms. Phenazine metabolites are known to play important roles in cellular functions; however, very little is known about how their concentrations fluctuate and influence cellular behaviors over the course of infection and growth. Herein we report the use of easily assembled, low-cost electrochemical sensors that provide rapid response times, enhanced sensitivity, and high reproducibility. As such, these T-CUAs enable real-time electrochemical monitoring of PYO and another extremely reactive and distinct redox-active phenazine metabolite, 5-methylphenazine-1-carboxylic acid (5-MCA), from a highly virulent laboratory P. aeruginosa strain, PA14. In addition to quantifying phenazine metabolite concentrations, changes in phenazine dynamics are observed in the biosynthetic route for the production of PYO. Our quantitative results, over a 48-h period, show increasing PYO concentrations during the first 21 h of bacterial growth, after which PYO levels plateau and then slightly decrease. Additionally, we explore environmental effects on phenazine dynamics and PYO concentrations in two growth media, tryptic soy broth (TSB) and lysogeny broth (LB). The maximum concentrations of cellular PYO were determined to be 190 ± 5 μM and 150 ± 1 μM in TSB and LB, respectively. Finally, using desorption electrospray ionization (DESI) and nanoelectrospray ionization (nano-ESI) mass spectrometry we confirm the detection and identification of reactive phenazine metabolites.
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Affiliation(s)
- Olja Simoska
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Marta Sans
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Mignon D. Fitzpatrick
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Christopher M. Crittenden
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Livia S. Eberlin
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Jason B. Shear
- Department of Chemistry, University of Texas at Austin, 1 University Station, Stop A5300, Austin, Texas 78712, United States
| | - Keith J. Stevenson
- Center for Electrochemical Energy Storage, Skolkovo Institute of Science and Technology, 3 Nobel Street, Moscow 143026, Russia
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11
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Meirelles LA, Newman DK. Both toxic and beneficial effects of pyocyanin contribute to the lifecycle of Pseudomonas aeruginosa. Mol Microbiol 2018; 110:995-1010. [PMID: 30230061 DOI: 10.1111/mmi.14132] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2018] [Indexed: 12/13/2022]
Abstract
Pseudomonas aeruginosa, an opportunistic pathogen, produces redox-active pigments called phenazines. Pyocyanin (PYO, the blue phenazine) plays an important role during biofilm development. Paradoxically, PYO auto-poisoning can stimulate cell death and release of extracellular DNA (eDNA), yet PYO can also promote survival within biofilms when cells are oxidant-limited. Here, we identify the environmental and physiological conditions in planktonic culture that promote PYO-mediated cell death. We demonstrate that PYO auto-poisoning is enhanced when cells are starved for carbon. In the presence of PYO, cells activate a set of genes involved in energy-dependent defenses, including: (i) the oxidative stress response, (ii) RND efflux systems and (iii) iron-sulfur cluster biogenesis factors. P. aeruginosa can avoid PYO poisoning when reduced carbon is available, but blockage of adenosine triphosphate (ATP) synthesis either through carbon limitation or direct inhibition of the F0 F1 -ATP synthase triggers death and eDNA release. Finally, even though PYO is toxic to the majority of the population when cells are nutrient limited, a subset of cells is intrinsically PYO resistant. The effect of PYO on the producer population thus appears to be dynamic, playing dramatically different yet predictable roles throughout distinct stages of growth, helping rationalize its multifaceted contributions to biofilm development.
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Affiliation(s)
- Lucas A Meirelles
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
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12
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Abstract
Descriptions of the changeable, striking colors associated with secreted natural products date back well over a century. These molecules can serve as extracellular electron shuttles (EESs) that permit microbes to access substrates at a distance. In this review, we argue that the colorful world of EESs has been too long neglected. Rather than simply serving as a diagnostic attribute of a particular microbial strain, redox-active natural products likely play fundamental, underappreciated roles in the biology of their producers, particularly those that inhabit biofilms. Here, we describe the chemical diversity and potential distribution of EES producers and users, discuss the costs associated with their biosynthesis, and critically evaluate strategies for their economical usage. We hope this review will inspire efforts to identify and explore the importance of EES cycling by a wide range of microorganisms so that their contributions to shaping microbial communities can be better assessed and exploited.
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Affiliation(s)
- Nathaniel R Glasser
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Scott H Saunders
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , , .,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125
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13
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Bhattacharjee A, Datta R, Gratton E, Hochbaum AI. Metabolic fingerprinting of bacteria by fluorescence lifetime imaging microscopy. Sci Rep 2017; 7:3743. [PMID: 28623341 PMCID: PMC5473825 DOI: 10.1038/s41598-017-04032-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 05/22/2017] [Indexed: 12/21/2022] Open
Abstract
Bacterial populations exhibit a range of metabolic states influenced by their environment, intra- and interspecies interactions. The identification of bacterial metabolic states and transitions between them in their native environment promises to elucidate community behavior and stochastic processes, such as antibiotic resistance acquisition. In this work, we employ two-photon fluorescence lifetime imaging microscopy (FLIM) to create a metabolic fingerprint of individual bacteria and populations. FLIM of autofluorescent reduced nicotinamide adenine dinucleotide (phosphate), NAD(P)H, has been previously exploited for label-free metabolic imaging of mammalian cells. However, NAD(P)H FLIM has not been established as a metabolic proxy in bacteria. Applying the phasor approach, we create FLIM-phasor maps of Escherichia coli, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus epidermidis at the single cell and population levels. The bacterial phasor is sensitive to environmental conditions such as antibiotic exposure and growth phase, suggesting that observed shifts in the phasor are representative of metabolic changes within the cells. The FLIM-phasor approach represents a powerful, non-invasive imaging technique to study bacterial metabolism in situ and could provide unique insights into bacterial community behavior, pathology and antibiotic resistance with sub-cellular resolution.
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Affiliation(s)
- Arunima Bhattacharjee
- Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA, 92697, USA
| | - Rupsa Datta
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Allon I Hochbaum
- Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA, 92697, USA.
- Department of Chemistry, University of California, Irvine, Irvine, CA, 92697, USA.
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14
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Glasser NR, Wang BX, Hoy JA, Newman DK. The Pyruvate and α-Ketoglutarate Dehydrogenase Complexes of Pseudomonas aeruginosa Catalyze Pyocyanin and Phenazine-1-carboxylic Acid Reduction via the Subunit Dihydrolipoamide Dehydrogenase. J Biol Chem 2017; 292:5593-5607. [PMID: 28174304 DOI: 10.1074/jbc.m116.772848] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/06/2017] [Indexed: 11/06/2022] Open
Abstract
Phenazines are a class of redox-active molecules produced by diverse bacteria and archaea. Many of the biological functions of phenazines, such as mediating signaling, iron acquisition, and redox homeostasis, derive from their redox activity. Although prior studies have focused on extracellular phenazine oxidation by oxygen and iron, here we report a search for reductants and catalysts of intracellular phenazine reduction in Pseudomonas aeruginosa Enzymatic assays in cell-free lysate, together with crude fractionation and chemical inhibition, indicate that P. aeruginosa contains multiple enzymes that catalyze the reduction of the endogenous phenazines pyocyanin and phenazine-1-carboxylic acid in both cytosolic and membrane fractions. We used chemical inhibitors to target general enzyme classes and found that an inhibitor of flavoproteins and heme-containing proteins, diphenyleneiodonium, effectively inhibited phenazine reduction in vitro, suggesting that most phenazine reduction derives from these enzymes. Using natively purified proteins, we demonstrate that the pyruvate and α-ketoglutarate dehydrogenase complexes directly catalyze phenazine reduction with pyruvate or α-ketoglutarate as electron donors. Both complexes transfer electrons to phenazines through the common subunit dihydrolipoamide dehydrogenase, a flavoprotein encoded by the gene lpdG Although we were unable to co-crystallize LpdG with an endogenous phenazine, we report its X-ray crystal structure in the apo-form (refined to 1.35 Å), bound to NAD+ (1.45 Å), and bound to NADH (1.79 Å). In contrast to the notion that phenazines support intracellular redox homeostasis by oxidizing NADH, our work suggests that phenazines may substitute for NAD+ in LpdG and other enzymes, achieving the same end by a different mechanism.
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Affiliation(s)
| | - Benjamin X Wang
- From the Divisions of Biology and Biological Engineering and
| | - Julie A Hoy
- From the Divisions of Biology and Biological Engineering and
| | - Dianne K Newman
- From the Divisions of Biology and Biological Engineering and .,Geology and Planetary Sciences, California Institute of Technology, Pasadena, California 91125
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15
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Costa KC, Glasser NR, Conway SJ, Newman DK. Pyocyanin degradation by a tautomerizing demethylase inhibits Pseudomonas aeruginosa biofilms. Science 2016; 355:170-173. [PMID: 27940577 DOI: 10.1126/science.aag3180] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/14/2016] [Accepted: 11/29/2016] [Indexed: 12/13/2022]
Abstract
The opportunistic pathogen Pseudomonas aeruginosa produces colorful redox-active metabolites called phenazines, which underpin biofilm development, virulence, and clinical outcomes. Although phenazines exist in many forms, the best studied is pyocyanin. Here, we describe pyocyanin demethylase (PodA), a hitherto uncharacterized protein that oxidizes the pyocyanin methyl group to formaldehyde and reduces the pyrazine ring via an unusual tautomerizing demethylation reaction. Treatment with PodA disrupts P. aeruginosa biofilm formation similarly to DNase, suggesting interference with the pyocyanin-dependent release of extracellular DNA into the matrix. PodA-dependent pyocyanin demethylation also restricts established biofilm aggregate populations experiencing anoxic conditions. Together, these results show that modulating extracellular redox-active metabolites can influence the fitness of a biofilm-forming microorganism.
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Affiliation(s)
- Kyle C Costa
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Nathaniel R Glasser
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Stuart J Conway
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. .,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
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16
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Electrochemical camera chip for simultaneous imaging of multiple metabolites in biofilms. Nat Commun 2016; 7:10535. [PMID: 26813638 PMCID: PMC4737866 DOI: 10.1038/ncomms10535] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 12/23/2015] [Indexed: 12/12/2022] Open
Abstract
Monitoring spatial distribution of metabolites in multicellular structures can enhance understanding of the biochemical processes and regulation involved in cellular community development. Here we report on an electrochemical camera chip capable of simultaneous spatial imaging of multiple redox-active phenazine metabolites produced by Pseudomonas aeruginosa PA14 colony biofilms. The chip features an 8 mm × 8 mm array of 1,824 electrodes multiplexed to 38 parallel output channels. Using this chip, we demonstrate potential-sweep-based electrochemical imaging of whole-biofilms at measurement rates in excess of 0.2 s per electrode. Analysis of mutants with various capacities for phenazine production reveals distribution of phenazine-1-carboxylic acid (PCA) throughout the colony, with 5-methylphenazine-1-carboxylic acid (5-MCA) and pyocyanin (PYO) localized to the colony edge. Anaerobic growth on nitrate confirms the O2-dependence of PYO production and indicates an effect of O2 availability on 5-MCA synthesis. This integrated-circuit-based technique promises wide applicability in detecting redox-active species from diverse biological samples.
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17
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Bellin DL, Sakhtah H, Rosenstein JK, Levine PM, Thimot J, Emmett K, Dietrich LEP, Shepard KL. Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms. Nat Commun 2015; 5:3256. [PMID: 24510163 PMCID: PMC3969851 DOI: 10.1038/ncomms4256] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 01/14/2014] [Indexed: 12/20/2022] Open
Abstract
Despite advances in monitoring spatiotemporal expression patterns of genes and proteins with fluorescent probes, direct detection of metabolites and small molecules remains challenging. A technique for spatially resolved detection of small molecules would benefit the study of redox-active metabolites produced by microbial biofilms, which can drastically affect colony development. Here we present an integrated circuit-based electrochemical sensing platform featuring an array of working electrodes and parallel potentiostat channels. “Images” over a 3.25 × 0.9 mm area can be captured with a diffusion-limited spatial resolution of 750 μm. We demonstrate that square wave voltammetry can be used to detect, identify, and quantify (for concentrations as low as 2.6 μM) four distinct redox-active metabolites called phenazines. We characterize phenazine production in both wild-type and mutant Pseudomonas aeruginosa PA14 colony biofilms, and find correlations with fluorescent reporter imaging of phenazine biosynthetic gene expression.
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Affiliation(s)
- Daniel L Bellin
- Department of Electrical Engineering, Columbia University, New York, New York 10027, USA
| | - Hassan Sakhtah
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Jacob K Rosenstein
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Peter M Levine
- Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
| | - Jordan Thimot
- Department of Electrical Engineering, Columbia University, New York, New York 10027, USA
| | - Kevin Emmett
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - Lars E P Dietrich
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Kenneth L Shepard
- 1] Department of Electrical Engineering, Columbia University, New York, New York 10027, USA [2] Department of Biomedical Engineering, Columbia University, New York, New York 10027, USA
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18
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Isolation of phenazine 1,6-di-carboxylic acid from Pseudomonas aeruginosa strain HRW.1-S3 and its role in biofilm-mediated crude oil degradation and cytotoxicity against bacterial and cancer cells. Appl Microbiol Biotechnol 2015; 99:8653-65. [PMID: 26051670 DOI: 10.1007/s00253-015-6707-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 04/08/2015] [Accepted: 05/19/2015] [Indexed: 10/23/2022]
Abstract
Pseudomonas sp. has long been known for production of a wide range of secondary metabolites during late exponential and stationary phases of growth. Phenazine derivatives constitute a large group of secondary metabolites produced by microorganisms including Pseudomonas sp. Phenazine 1,6-di-carboxylic acid (PDC) is one of such metabolites and has been debated for its origin from Pseudomonas sp. The present study describes purification and characterization of PDC isolated from culture of a natural isolate of Pseudomonas sp. HRW.1-S3 while grown in presence of crude oil as sole carbon source. The isolated PDC was tested for its effect on biofilm formation by another environmental isolate of Pseudomonas sp. DSW.1-S4 which lacks the ability to produce any phenazine compound. PDC showed profound effect on both planktonic as well as biofilm mode of growth of DSW.1-S4 at concentrations between 5 and 20 μM. Interestingly, PDC showed substantial cytotoxicity against three cancer cell lines and against both Gram-positive and Gram-negative bacteria. Thus, the present study not only opens an avenue to understand interspecific cooperation between Pseudomonas species which may lead its applicability in bioremediation, but also it signifies the scope of future investigation on PDC for its therapeutic applications.
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19
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Abstract
Certain pseudomonads are capable of producing phenazines-pigmented, reversibly redox-active metabolites that induce a variety of physiological effects on the producing organism as well as others in their vicinity. Environmental conditions and the specific physiological state of cells can dramatically affect the absolute amounts and relative proportions of the various phenazines produced. The method detailed here-high-performance liquid chromatography coupled to detection by UV-Vis absorption-can be used to separate and quantify the amount of phenazines in a Pseudomonas culture. Simple spectrophotometric measurements of filtered culture supernatants can be used to quantify certain oxidized phenazines, such as pyocyanin, in cultures. For cases where the conditions under study are not planktonic cultures (e.g., soil or biofilms) extracting the phenazines may be a necessary first step.
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Affiliation(s)
- Suzanne E Kern
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
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20
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Abstract
Nicotinamide adenine dinucleotides are critical redox-active substrates for countless catabolic and anabolic reactions. Ratios of NAD(+) to NADH and NADP(+) to NADPH are therefore considered key indicators of the overall intracellular redox potential and metabolic state. These ratios can be measured in bulk conditions using a highly sensitive enzyme cycling-based colorimetric assay (detection limit at or below 0.05 μM or 1 pmol) following a simple extraction procedure involving solutions of acid and base. Special considerations are necessary to avoid measurement artifacts caused by the presence of endogenous redox-active metabolites, such as phenazines made by diverse Pseudomonas species (see Chapter 25).
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21
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Rainey PB, Desprat N, Driscoll WW, Zhang XX. Microbes are not bound by sociobiology: response to Kümmerli and Ross-Gillespie (2013). Evolution 2014; 68:3344-55. [PMID: 25141778 DOI: 10.1111/evo.12508] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/02/2014] [Indexed: 11/30/2022]
Abstract
In recent years, sociobiology has been extended to microorganisms. Viewed through this lens, the microbial world is replete with cooperative behaviors. However, little attention has been paid to alternate hypotheses, making many studies self-confirming. Somewhat apart is a recent analysis of pyoverdin production-a paradigmatic public good and social trait-by Pseudomonas, which has revealed discord between predictions arising from sociobiology and the biology of microbes. This led the authors, Zhang and Rainey (Z&R), to question the generality of the conclusion that pyoverdin is a social trait, and to question the fit between the sociobiology framework and microbiology. This has unsettled Kümmerli and Ross-Gillespie (K&R), who in a recent "Technical Comment" assert that arguments presented by Z&R are flawed, their experiments technically mistaken, and their understanding of social evolution theory naive. We demonstrate these claims to be without substance and show the conclusions of K&R to be based on a lack of understanding of redox chemistry and on misinterpretation of data. We also point to evidence of cherry-picking and raise the possibility of confirmation bias. Finally, we emphasize that the sociobiology framework applied to microbes is a hypothesis that requires rigorous and careful appraisal.
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Affiliation(s)
- Paul B Rainey
- New Zealand Institute for Advanced Study, Allan Wilson Centre for Molecular Ecology & Evolution, Massey University, Private Bag 102904, Auckland, 0745, New Zealand; Max Planck Institute for Evolutionary Biology, August Thienemann Strasse 2, 24306, Plön, Germany.
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Glasser NR, Kern SE, Newman DK. Phenazine redox cycling enhances anaerobic survival in Pseudomonas aeruginosa by facilitating generation of ATP and a proton-motive force. Mol Microbiol 2014; 92:399-412. [PMID: 24612454 PMCID: PMC4046897 DOI: 10.1111/mmi.12566] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2014] [Indexed: 01/01/2023]
Abstract
While many studies have explored the growth of Pseudomonas aeruginosa, comparatively few have focused on its survival. Previously, we reported that endogenous phenazines support the anaerobic survival of P. aeruginosa, yet the physiological mechanism underpinning survival was unknown. Here, we demonstrate that phenazine redox cycling enables P. aeruginosa to oxidize glucose and pyruvate into acetate, which promotes survival by coupling acetate and ATP synthesis through the activity of acetate kinase. By measuring intracellular NAD(H) and ATP concentrations, we show that survival is correlated with ATP synthesis, which is tightly coupled to redox homeostasis during pyruvate fermentation but not during arginine fermentation. We also show that ATP hydrolysis is required to generate a proton-motive force using the ATP synthase complex during fermentation. Together, our results suggest that phenazines enable maintenance of the proton-motive force by promoting redox homeostasis and ATP synthesis. This work demonstrates the more general principle that extracellular redox-active molecules, such as phenazines, can broaden the metabolic versatility of microorganisms by facilitating energy generation.
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Affiliation(s)
- Nathaniel R Glasser
- Division of Biology and Biological Engineering, California Institute of Technology and Howard Hughes Medical Institute, Pasadena, CA, USA
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23
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Bacterial community morphogenesis is intimately linked to the intracellular redox state. J Bacteriol 2013; 195:1371-80. [PMID: 23292774 DOI: 10.1128/jb.02273-12] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Many microbial species form multicellular structures comprising elaborate wrinkles and concentric rings, yet the rules governing their architecture are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa produces phenazines, small molecules that act as alternate electron acceptors to oxygen and nitrate to oxidize the intracellular redox state and that influence biofilm morphogenesis. Here, we show that the depth occupied by cells within colony biofilms correlates well with electron acceptor availability. Perturbations in the environmental provision, endogenous production, and utilization of electron acceptors affect colony development in a manner consistent with redox control. Intracellular NADH levels peak before the induction of colony wrinkling. These results suggest that redox imbalance is a major factor driving the morphogenesis of P. aeruginosa biofilms and that wrinkling itself is an adaptation that maximizes oxygen accessibility and thereby supports metabolic homeostasis. This type of redox-driven morphological change is reminiscent of developmental processes that occur in metazoans.
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KynR, a Lrp/AsnC-type transcriptional regulator, directly controls the kynurenine pathway in Pseudomonas aeruginosa. J Bacteriol 2011; 193:6567-75. [PMID: 21965577 DOI: 10.1128/jb.05803-11] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa can utilize a variety of carbon sources and produces many secondary metabolites to help survive harsh environments. P. aeruginosa is part of a small group of bacteria that use the kynurenine pathway to catabolize tryptophan. Through the kynurenine pathway, tryptophan is broken down into anthranilate, which is further degraded into tricarboxylic acid cycle intermediates or utilized to make numerous aromatic compounds, including the Pseudomonas quinolone signal (PQS). We have previously shown that the kynurenine pathway is a critical source of anthranilate for PQS synthesis and that the kynurenine pathway genes (kynA and kynBU) are upregulated in the presence of kynurenine. A putative Lrp/AsnC-type transcriptional regulator (gene PA2082, here called kynR), is divergently transcribed from the kynBU operon and is highly conserved in gram-negative bacteria that harbor the kynurenine pathway. We show that a mutation in kynR renders P. aeruginosa unable to utilize L-tryptophan as a sole carbon source and decreases PQS production. In addition, we found that the increase of kynA and kynB transcriptional activity in response to kynurenine was completely abolished in a kynR mutant, further indicating that KynR mediates the kynurenine-dependent expression of the kynurenine pathway genes. Finally, we found that purified KynR specifically bound the kynA promoter in the presence of kynurenine and bound the kynB promoter in the absence or presence of kynurenine. Taken together, our data show that KynR directly regulates the kynurenine pathway genes.
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