Optical O
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            Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria

Flamholz, Avi I.; Saccomano, Samuel C.; Cash, Kevin J.; Newman, Dianne K.

doi:10.1128/mbio.02076-22

Cited by 7 publications

(6 citation statements)

References 25 publications

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“…However, there was no difference in reduction rates on different sugars at pH 7.5 and in some cases reduction rates appeared higher on pyruvate than on the other sugars, an observation that has been made in other experimental contexts ( 29 ). Direct measurements of oxygen in our experiments are not possible given current technologies ( 49 ) as any disturbance in shaking would alter oxygen tensions precluding an accurate measurement of the oxygen concentrations experienced by cells. Succinate and pyruvate are both organic acids, and despite medium buffering (which cannot be increased due to toxicity concerns), it is also possible that shifts toward more alkaline pH during growth on these substrates further decrease PCA reduction ( 50 ).…”

Section: Resultsmentioning

confidence: 99%

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

McRose

Newman

2023

Proc. Natl. Acad. Sci. U.S.A.

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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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Section: Resultsmentioning

confidence: 99%

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

McRose

Newman

2023

Proc. Natl. Acad. Sci. U.S.A.

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“…Previous studies have used nanosensors 24 , electrochemical profiling [25][26][27] and Pcco2-mediated biosensing 25,28 to study the oxygen gradients and redox profile of P. aeruginosa biofilms. While these studies have provided robust insights into the chemical microenvironment within the bulk mass of pseudomonad biofilms, the void structures of E. coli transport channels presented a priority for this study which would inform if the local conditions might impact on future channel-exploiting treatments.…”

Section: Discussionmentioning

confidence: 99%

“…recently documented the common pitfalls in oxygen nanosensing applications in biofilms, where the constituent cells can produce quenching molecules that may impact on the reliability of optical oxygen quantifications 24 . We therefore provided a spatial overview of the relative change in nanosensor intensity as a function of oxygen depletion along biofilm transport channels and supplemented this ratiometric data with high resolution electrochemical sensing experiments.…”

Section: Discussionmentioning

confidence: 99%

Oxygen Microenvironments inE. coliBiofilm Nutrient Transport Channels: Insights from Complementary Sensing Approaches

Bottura,

McConnell,

Florek

et al. 2024

Preprint

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Chemical gradients and the emergence of distinct microenvironments in biofilms are vital to the stratification, maturation and overall function of microbial communities. These gradients have been well characterised throughout the biofilm mass but the microenvironment of recently discovered nutrient transporting channels inEscherichia colibiofilms remains unexplored. This study employs three different oxygen sensing approaches to provide a robust quantitative overview of the oxygen gradients and microenvironments throughout the biofilm transport channel networks formed byE. colimacrocolony biofilms. Oxygen nanosensing combined with confocal laser scanning microscopy established that the oxygen concentration changes along the length of biofilm transport channels. Electrochemical sensing provided precise quantification of the oxygen profile in the transport channels, showing similar anoxic profiles compared with the adjacent cells. Anoxic biosensing corroborated these approaches, providing an overview of the oxygen utilisation throughout the biomass. The discovery that transport channels maintain oxygen gradients contradicts the previous literature that channels are completely open to the environment along the apical surface of the biofilm. We provide a potential mechanism for the sustenance of channel microenvironments via orthogonal visualisations of biofilm thin sections showing thin layers of actively growing cells. This complete overview of the oxygen environment in biofilm transport channels primes future studies aiming to exploit these emergent structures for new bioremediation approaches.

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“…E. coli BL21 (DE3) were used as the model suspension culture system, where it was recently reported that secreted molecules from E. coli do not affect the behavior of porphyrin-based oxygen nanosensors. 40 Different concentrations of bacteria were cultured over a 15 h period with the oxygen levels monitored continuously. As the number of cells in suspension increased, the added effects of respiration and oxygen depletion also increased, as shown in Figure 5A.…”

Section: Acs Sensorsmentioning

confidence: 99%

Organosilica Nanosensors for Monitoring Spatiotemporal Changes in Oxygen Levels in Bacterial Cultures

Huynh,

Tunny,

Frith

et al. 2024

ACS Sens.

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Oxygen plays a central role in aerobic metabolism, and while many approaches have been developed to measure oxygen concentration in biological environments over time, monitoring spatiotemporal changes in dissolved oxygen levels remains challenging. To address this, we developed a ratiometric core−shell organosilica nanosensor for continuous, real-time optical monitoring of oxygen levels in biological environments. The nanosensors demonstrate good steady state characteristics (K pSV = 0.40 L/mg, R 2 = 0.95) and respond reversibly to changes in oxygen concentration in buffered solutions and report similar oxygen level changes in response to bacterial cell growth (Escherichia coli) in comparison to a commercial bulk optodebased sensing film. We further demonstrated that the oxygen nanosensors could be distributed within a growing culture of E. coli and used to record oxygen levels over time and in different locations within a static culture, opening the possibility of spatiotemporal monitoring in complex biological systems.

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Optical O ₂ Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria

Abstract: When they are closely packed, as in biofilms, colonies, and soils, microbes can consume O 2 faster than it diffuses. As such, O 2 concentrations in natural environments can vary greatly over time and space, even on the micrometer scale.

Cited by 7 publications

References 25 publications

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

Oxygen Microenvironments inE. coliBiofilm Nutrient Transport Channels: Insights from Complementary Sensing Approaches

Organosilica Nanosensors for Monitoring Spatiotemporal Changes in Oxygen Levels in Bacterial Cultures

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Optical O 2 Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria

Abstract: When they are closely packed, as in biofilms, colonies, and soils, microbes can consume O 2 faster than it diffuses. As such, O 2 concentrations in natural environments can vary greatly over time and space, even on the micrometer scale.

Cited by 7 publications

References 25 publications

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

The chemical ecology of coumarins and phenazines affects iron acquisition by pseudomonads

Oxygen Microenvironments inE. coliBiofilm Nutrient Transport Channels: Insights from Complementary Sensing Approaches

Organosilica Nanosensors for Monitoring Spatiotemporal Changes in Oxygen Levels in Bacterial Cultures

Contact Info

Product

Resources

About

Optical O ₂ Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria