Endogenous phenazine-1-carboxamide encoding gene PhzH regulated the extracellular electron transfer in biocorrosion of stainless steel by marine Pseudomonas aeruginosa

<p>Microbial nanowires are nanofilaments that could offer an extracellular electron transfer (EET) pathway linking the bacterial respiratory chain to external surfaces, such as oxidized metals in the environment and engineered electrodes in renewable energy devices. Filaments proposed to function as nanowires have been reported in multiple bacteria, yet it remains largely unclear about the composition and electron transfer mechanism of bacterial nanowires. Pseudomonas aeruginosa is an environmental and electrochemically active bacterium. In this study, we found nanotube-like extracellular filaments in P. aeruginosa biofilms, which were bacterial membrane extensions similar to the nanowires reported in Shewanella oneidensis. Remarkably, conductive probe atomic force microscope showed measurable conductivity of these extracellular filaments, suggesting that they may function as nanowires in P. aeruginosa. Our results also indicated that the electron shuttle pyocyanin significantly affected the conductivity of P. aeruginosa nanowires, suggesting that the electron transfer mechanism of P. aeruginosa nanowires was different from S. oneidensis. Furthermore, factors that impact biofilm formation, such as flagella, type IV pili, and exopolysaccharides, were not essential for nanowires formation, while affect the formation and length of nanowires of P. aeruginosa. Taken together, this is the first report that investigated the role of electron shuttle on the conductivity of nanowires and factors that affected nanowires formation.</p>

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Adaptive Evolution of Geobacter sulfurreducens in Coculture with Pseudomonas aeruginosa

mBio ◽

10.1128/mbio.02875-19 ◽

2020 ◽

Vol 11 (2) ◽

Author(s):

Lucie Semenec ◽

Ismael A. Vergara ◽

Andrew E. Laloo ◽

Steve Petrovski ◽

Philip L. Bond ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Electron Transfer ◽

Adaptive Evolution ◽

Efflux Pump ◽

Antibiotic Production ◽

Geobacter Sulfurreducens ◽

Extracellular Electron Transfer ◽

Content Type ◽

Interaction Dynamics ◽

Syntrophic Interaction

ABSTRACT Interactions between microorganisms in mixed communities are highly complex, being either syntrophic, neutral, predatory, or competitive. Evolutionary changes can occur in the interaction dynamics between community members as they adapt to coexistence. Here, we report that the syntrophic interaction between Geobacter sulfurreducens and Pseudomonas aeruginosa coculture change in their dynamics over evolutionary time. Specifically, Geobacter sp. dominance increases with adaptation within the cocultures, as determined through quantitative PCR and fluorescence in situ hybridization. This suggests a transition from syntrophy to competition and demonstrates the rapid adaptive capacity of Geobacter spp. to dominate in cocultures with P. aeruginosa. Early in coculture establishment, two single-nucleotide variants in the G. sulfurreducens fabI and tetR genes emerged that were strongly selected for throughout coculture evolution with P. aeruginosa phenazine wild-type and phenazine-deficient mutants. Sequential window acquisition of all theoretical spectra-mass spectrometry (SWATH-MS) proteomics revealed that the tetR variant cooccurred with the upregulation of an adenylate cyclase transporter, CyaE, and a resistance-nodulation-division (RND) efflux pump notably known for antibiotic efflux. To determine whether antibiotic production was driving the increased expression of the multidrug efflux pump, we tested Pseudomonas-derived phenazine-1-carboxylic acid (PHZ-1-CA) for its potential to inhibit Geobacter growth and drive selection of the tetR and fabI genetic variants. Despite its inhibitory properties, PHZ-1-CA did not drive variant selection, indicating that other antibiotics may drive overexpression of the efflux pump and CyaE or that a novel role exists for these proteins in the context of this interaction. IMPORTANCE Geobacter and Pseudomonas spp. cohabit many of the same environments, where Geobacter spp. often dominate. Both bacteria are capable of extracellular electron transfer (EET) and play important roles in biogeochemical cycling. Although they recently in 2017 were demonstrated to undergo direct interspecies electron transfer (DIET) with one another, the genetic evolution of this syntrophic interaction has not been examined. Here, we use whole-genome sequencing of the cocultures before and after adaptive evolution to determine whether genetic selection is occurring. We also probe their interaction on a temporal level and determine whether their interaction dynamics change over the course of adaptive evolution. This study brings to light the multifaceted nature of interactions between just two microorganisms within a controlled environment and will aid in improving metabolic models of microbial communities comprising these two bacteria.

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Enhanced Mechanism of Extracellular Electron Transfer between Semiconducting Minerals Anatase and Pseudomonas aeruginosa PAO1 in Euphotic Zone

Bioelectrochemistry ◽

10.1016/j.bioelechem.2021.107849 ◽

2021 ◽

pp. 107849

Author(s):

Jia Liu ◽

Xi Liu ◽

Hongrui Ding ◽

Guiping Ren ◽

Yuan Sun ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Electron Transfer ◽

Euphotic Zone ◽

Extracellular Electron Transfer ◽

Pseudomonas Aeruginosa Pao1

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Significance of extracellular polymeric substances, reactive oxygen species, and expression of extracellular electron transfer genes on methanogenic activity in biocathode

10.1101/2020.11.12.380824 ◽

2020 ◽

Author(s):

Basem S. Zakaria ◽

Bipro Ranjan Dhar

Keyword(s):

Reactive Oxygen Species ◽

Stainless Steel ◽

Electron Transfer ◽

Carbon Fiber ◽

Microbial Communities ◽

Extracellular Polymeric Substances ◽

Reactive Oxygen ◽

Extracellular Electron Transfer ◽

Oxygen Species ◽

Methanogenic Activity

AbstractThis study presents a multifaceted approach combining characterization of microbial communities, extracellular polymeric substances (EPS), reactive oxygen species (ROS), and expression of genes associated with extracellular electron transfer (EET) to shed light on their significance on electro-methanogenic activity in different biocathode materials. Carbon fiber and stainless-steel mesh biocathode were tested in microbial electrolysis cell assisted anaerobic digestion (MEC-AD) systems fed with synthetic glucose medium. Despite the higher specific surface area provided by carbon fiber biocathode, methanogenesis performance was much inferior (100.3 mL CH4) than that obtained from a stainless steel biocathode (179.5 mL CH4) operated under the same operating conditions. Interestingly, biofilms did not entirely cover the surfaces of carbon fibers, while stainless steel biocathode showed evenly denser biofilms with higher biovolume (30.2±4.2 vs. 13.5±2.8 μm3/μm2). Analyses of microbial communities indicated that the key mechanism for electro-methanogenesis in both reactors was hydrogenotrophic methanogenesis by Methanobacterium species. Along with the effective catalysis of hydrogen evolution reaction (HER), a higher abundance of known hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium appeared to play a major role in superior methanogenesis on stainless steel biocathode. The most considerable secretion of EPS accompanied by the lowest ROS level in stainless steel biocathode indicated that higher EPS possibly protected cells from harsh metabolic conditions (e.g., unfavorable local pH) induced by faster HER. Moreover, the redox activity of EPS derived from biocathode, as well as expressions of EET genes, suggested that electro-methanogenesis via direct electron transfer might have occurred to some extent in both biocathodes. Overall, the results of this study have important significance in the development of effective biocathode for MEC-AD systems.

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Extracellular DNA promotes efficient extracellular electron transfer by pyocyanin in Pseudomonas aeruginosa biofilms

10.1101/2019.12.12.872085 ◽

2019 ◽

Cited By ~ 1

Author(s):

Scott H. Saunders ◽

Edmund C.M. Tse ◽

Matthew D. Yates ◽

Fernanda Jiménez Otero ◽

Scott A. Trammell ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Electron Transfer ◽

Redox Reactions ◽

Extracellular Dna ◽

Extracellular Electron Transfer ◽

Bacterial Biofilms ◽

Active Metabolites ◽

Electron Shuttles ◽

Redox Active

SUMMARYExtracellular electron transfer (EET), the process whereby cells access electron acceptors or donors that reside many cell lengths away, enables metabolic activity by microorganisms, particularly under oxidant-limited conditions that occur in multicellular bacterial biofilms. Although different mechanisms underpin this process in select organisms, a widespread strategy involves extracellular electron shuttles, redox-active metabolites that are secreted and recycled by diverse bacteria. How these shuttles catalyze electron transfer within biofilms without being lost to the environment has been a long-standing question. Here, we show that phenazine electron shuttles mediate efficient EET through interactions with extracellular DNA (eDNA) in Pseudomonas aeruginosa biofilms, which are important in nature and disease. Retention of pyocyanin (PYO) and phenazine carboxamide in the biofilm matrix is facilitated by binding to eDNA. In vitro, different phenazines can exchange electrons in the presence or absence of DNA and phenazines can participate directly in redox reactions through DNA; the biofilm eDNA can also support rapid electron transfer between redox active intercalators. Electrochemical measurements of biofilms indicate that retained PYO supports an efficient redox cycle with rapid EET and slow loss from the biofilm. Together, these results establish that eDNA facilitates phenazine metabolic processes in P. aeruginosa biofilms, suggesting a model for how extracellular electron shuttles achieve retention and efficient EET in biofilms.

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Endogenous Phenazine Antibiotics Promote Anaerobic Survival of Pseudomonas aeruginosa via Extracellular Electron Transfer

Journal of Bacteriology ◽

10.1128/jb.01188-09 ◽

2009 ◽

Vol 192 (1) ◽

pp. 365-369 ◽

Cited By ~ 169

Author(s):

Yun Wang ◽

Suzanne E. Kern ◽

Dianne K. Newman

Keyword(s):

Pseudomonas Aeruginosa ◽

Electron Transfer ◽

Community Development ◽

Extracellular Electron Transfer ◽

Physiological Functions ◽

Electron Shuttles ◽

Survival Effect ◽

Phenazine Antibiotics

ABSTRACT Antibiotics are increasingly recognized as having other, important physiological functions for the cells that produce them. An example of this is the effect that phenazines have on signaling and community development for Pseudomonas aeruginosa (L. E. Dietrich, T. K. Teal, A. Price-Whelan, and D. K. Newman, Science 321:1203-1206, 2008). Here we show that phenazine-facilitated electron transfer to poised-potential electrodes promotes anaerobic survival but not growth of Pseudomonas aeruginosa PA14 under conditions of oxidant limitation. Other electron shuttles that are reduced but not made by PA14 do not facilitate survival, suggesting that the survival effect is specific to endogenous phenazines.

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Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

Scientific Reports ◽

10.1038/s41598-021-87118-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Basem S. Zakaria ◽

Bipro Ranjan Dhar

Keyword(s):

Reactive Oxygen Species ◽

Stainless Steel ◽

Electron Transfer ◽

Anaerobic Digestion ◽

Carbon Fibers ◽

Extracellular Polymeric Substances ◽

Expression Patterns ◽

Reactive Oxygen ◽

Extracellular Electron Transfer ◽

Oxygen Species

AbstractThe microbial electrolysis cell assisted anaerobic digestion holds great promises over conventional anaerobic digestion. This article reports an experimental investigation of extracellular polymeric substances (EPS), reactive oxygen species (ROS), and the expression of genes associated with extracellular electron transfer (EET) in methanogenic biocathodes. The MEC-AD systems were examined using two cathode materials: carbon fibers and stainless-steel mesh. A higher abundance of hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium sp. appeared to play a major role in superior methanogenesis from stainless steel biocathode than carbon fibers. Moreover, the higher secretion of EPS accompanied by the lower ROS level in stainless steel biocathode indicated that higher EPS perhaps protected cells from harsh metabolic conditions (possibly unfavorable local pH) induced by faster catalysis of hydrogen evolution reaction. In contrast, EET-associated gene expression patterns were comparable in both biocathodes. Thus, these results indicated hydrogenotrophic methanogenesis is the key mechanism, while cathodic EET has a trivial role in distinguishing performances between two cathode electrodes. These results provide new insights into the efficient methanogenic biocathode development.

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