Mechanical compression induces persistent bacterial growth during bacteriophage predation
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Abstract
Although the relationship between bacteria and lytic bacteriophage is fundamentally antagonistic, these microbes not only coexist but thrive side-by-side in myriad ecological environments. The mechanisms by which coexistence is achieved, however, are not fully understood. By examining Escherichia coli and bacteriophage T7 population dynamics at the single-cell and single-virion level using a novel microfluidics-based assay, we observed bacteria growing “persistently” when perfused with high-titer bacteriophage. Persistence occurred at a frequency five orders of magnitude higher than is expected from natural selection of bacteriophage-resistant mutants. Rather, the frequency of persistence was correlated with the degree to which the bacteria were mechanically compressed by the microfluidic perfusion chamber. Using a combination of mutagenesis and fluorescent imaging techniques, we found that compression induces persistence by activating the Rcs phosphorelay pathway, which results in the synthesis of extracellular capsule that sterically blocks bacteriophage adsorption. Other forms of mechanical stimulation also promoted Rcs activity and persistence. These findings have important implications for our understanding of microbial ecology in many important environments, including the gut and the soil, where bacteria grow in confinement.
Significance Statement
Bacteria and bacteriophage form one of the most fundamental and important predator-prey relationships on earth, yet the factors that promote long-term stability of their populations are unknown. Here, we demonstrate that Escherichia coli is able to rapidly grow during bacteriophage predation if they are doing so in spatially confined environments. This discovery revises our understanding of bacteria-bacteriophage population dynamics in many real-world environments where bacteria grow in such environments, such as the gut and the soil. Additionally, this result has critical implications for the potential of antibacterial therapies to function during pathogenesis, when bacteria are also mechanically stimulated.
Article activity feed
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General comments:
This is an interesting manuscript describing the effect of mechanical stress on the relationship between bacteria and phages. The findings in this paper are valuable and improve our broad understanding of mechanobiology. Specifically, I want to compliment the authors on developing a unique experimental setup which would allow scientists to monitor continuously the effect of mechanical stress on bacteria over tens of hours. I also agree with the authors that there could be potential translational value of their findings that may allow us as a society to address antimicrobial resistance more effectively. I believe the paper is well-written and the conclusions are substantiated by the experiments presented here.
Specific comments:
You make the following statement on page 8 of the paper PDF “The frequency at which this …
General comments:
This is an interesting manuscript describing the effect of mechanical stress on the relationship between bacteria and phages. The findings in this paper are valuable and improve our broad understanding of mechanobiology. Specifically, I want to compliment the authors on developing a unique experimental setup which would allow scientists to monitor continuously the effect of mechanical stress on bacteria over tens of hours. I also agree with the authors that there could be potential translational value of their findings that may allow us as a society to address antimicrobial resistance more effectively. I believe the paper is well-written and the conclusions are substantiated by the experiments presented here.
Specific comments:
You make the following statement on page 8 of the paper PDF “The frequency at which this occurs depends on the flow rate used to load the cells into the chamber, allowing us to deliberately wedge cells into very narrow areas of the chamber.” I was wondering if it would be possible to include the data you used to determine this?
Would it be possible to include statistical significance for panels C and D in Figure 2? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness. This could be a supplementary figure.
In Figure 3 panel C, you refer to “persisters” and “non-persisters”. I was wondering if you are referring to the strain that is a “capsule k.o.” and the strain that is “capsule o.e.”? Could you please clarify this?
Would it be possible to include statistical significance for panel E in Figure 3? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness.
Would it be possible to include statistical significance for panel C in Figure 4? And how about for panels D and E in the same figure (perhaps just for the last time points)? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness.
Questions:
Would it be possible to prepare the compression setup with different materials or resins? It could provide broader utility if scientists could 3D-print their own compression devices of different sizes and different materials.
Additionally, the compression setups made from different materials may be able to help you understand better the damage inflicted on the bacterial membrane. This could let you get at the question of what mechanoreceptors might be involved here? I understand this is beyond the scope of this paper but, as you have indicated in your discussion, it is relevant to mechanosensing more broadly.
Regarding your compression setup, would it possible to determine if the bacteria are in a biofilm? This may help you determine what percentage of the persistence is due to biofilm versus the mechanical compression. I completely realize this is beyond the scope of this study but may be in a future study you could include a strain that cannot form biofilms and test it using the same compression setup.
I was wondering if the compression setup you developed could be applied to other bacteria, specifically non-rod-shaped bacteria like Borrelia burgdorferi? And how about to other cell types altogether? I wonder if this type of mechanosensing could trigger protective responses in other unicellular organisms, may be protists or algae!
Do you think there may be other persistence mechanisms triggered by mechanosensing? Specifically, do you think the cell wall may be undergoing some restructuring as well as the capsule? It would be interesting if the cell wall does but equally interesting if it does not!
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General comments:
This is an interesting manuscript describing the effect of mechanical stress on the relationship between bacteria and phages. The findings in this paper are valuable and improve our broad understanding of mechanobiology. Specifically, I want to compliment the authors on developing a unique experimental setup which would allow scientists to monitor continuously the effect of mechanical stress on bacteria over tens of hours. I also agree with the authors that there could be potential translational value of their findings that may allow us as a society to address antimicrobial resistance more effectively. I believe the paper is well-written and the conclusions are substantiated by the experiments presented here.
Specific comments:
You make the following statement on page 8 of the paper PDF “The frequency at which this …
General comments:
This is an interesting manuscript describing the effect of mechanical stress on the relationship between bacteria and phages. The findings in this paper are valuable and improve our broad understanding of mechanobiology. Specifically, I want to compliment the authors on developing a unique experimental setup which would allow scientists to monitor continuously the effect of mechanical stress on bacteria over tens of hours. I also agree with the authors that there could be potential translational value of their findings that may allow us as a society to address antimicrobial resistance more effectively. I believe the paper is well-written and the conclusions are substantiated by the experiments presented here.
Specific comments:
You make the following statement on page 8 of the paper PDF “The frequency at which this occurs depends on the flow rate used to load the cells into the chamber, allowing us to deliberately wedge cells into very narrow areas of the chamber.” I was wondering if it would be possible to include the data you used to determine this?
Would it be possible to include statistical significance for panels C and D in Figure 2? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness. This could be a supplementary figure.
In Figure 3 panel C, you refer to “persisters” and “non-persisters”. I was wondering if you are referring to the strain that is a “capsule k.o.” and the strain that is “capsule o.e.”? Could you please clarify this?
Would it be possible to include statistical significance for panel E in Figure 3? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness.
Would it be possible to include statistical significance for panel C in Figure 4? And how about for panels D and E in the same figure (perhaps just for the last time points)? The data look sufficiently tight and I don’t doubt the results but this would be nice to have for completeness.
Questions:
Would it be possible to prepare the compression setup with different materials or resins? It could provide broader utility if scientists could 3D-print their own compression devices of different sizes and different materials.
Additionally, the compression setups made from different materials may be able to help you understand better the damage inflicted on the bacterial membrane. This could let you get at the question of what mechanoreceptors might be involved here? I understand this is beyond the scope of this paper but, as you have indicated in your discussion, it is relevant to mechanosensing more broadly.
Regarding your compression setup, would it possible to determine if the bacteria are in a biofilm? This may help you determine what percentage of the persistence is due to biofilm versus the mechanical compression. I completely realize this is beyond the scope of this study but may be in a future study you could include a strain that cannot form biofilms and test it using the same compression setup.
I was wondering if the compression setup you developed could be applied to other bacteria, specifically non-rod-shaped bacteria like Borrelia burgdorferi? And how about to other cell types altogether? I wonder if this type of mechanosensing could trigger protective responses in other unicellular organisms, may be protists or algae!
Do you think there may be other persistence mechanisms triggered by mechanosensing? Specifically, do you think the cell wall may be undergoing some restructuring as well as the capsule? It would be interesting if the cell wall does but equally interesting if it does not!
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