Limits...
Metabolic co-dependence gives rise to collective oscillations within biofilms.

Liu J, Prindle A, Humphries J, Gabalda-Sagarra M, Asally M, Lee DY, Ly S, Garcia-Ojalvo J, Süel GM - Nature (2015)

Bottom Line: It remains unclear how these opposing interactions are resolved at the population level.We discover that this conflict between protection and starvation is resolved through emergence of long-range metabolic co-dependence between peripheral and interior cells.As a result, biofilm growth halts periodically, increasing nutrient availability for the sheltered interior cells.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, University of California San Diego, California 92093, USA.

ABSTRACT
Cells that reside within a community can cooperate and also compete with each other for resources. It remains unclear how these opposing interactions are resolved at the population level. Here we investigate such an internal conflict within a microbial (Bacillus subtilis) biofilm community: cells in the biofilm periphery not only protect interior cells from external attack but also starve them through nutrient consumption. We discover that this conflict between protection and starvation is resolved through emergence of long-range metabolic co-dependence between peripheral and interior cells. As a result, biofilm growth halts periodically, increasing nutrient availability for the sheltered interior cells. We show that this collective oscillation in biofilm growth benefits the community in the event of a chemical attack. These findings indicate that oscillations support population-level conflict resolution by coordinating competing metabolic demands in space and time, suggesting new strategies to control biofilm growth.

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Measurements of cell growth within oscillating biofilms. a, (Top) Visual representation of the method through which difference movies are generated (Methods: Data Analysis). Growth is represented by white pixels, and lack of growth is indicated by black pixels. (Middle) Film strip and (bottom) growth area over time of an oscillating colony. Dashed lines show the position of each image on the time trace. Scale bar represents 100 µm. b, (Top left) schematic of a biofilm. (Top right) high magnification phase contrast image of biofilm periphery focused at the bottom layer of cells. (Bottom panel) time traces depicting elongation rates of single cells in gray. Highlighted in red is the single cell time trace for the cell outlined in red in the top right panel. The periodic slowdown of the growth of individual peripheral cells is responsible for the observed periodic reduction in biofilm expansion.
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Figure 8: Measurements of cell growth within oscillating biofilms. a, (Top) Visual representation of the method through which difference movies are generated (Methods: Data Analysis). Growth is represented by white pixels, and lack of growth is indicated by black pixels. (Middle) Film strip and (bottom) growth area over time of an oscillating colony. Dashed lines show the position of each image on the time trace. Scale bar represents 100 µm. b, (Top left) schematic of a biofilm. (Top right) high magnification phase contrast image of biofilm periphery focused at the bottom layer of cells. (Bottom panel) time traces depicting elongation rates of single cells in gray. Highlighted in red is the single cell time trace for the cell outlined in red in the top right panel. The periodic slowdown of the growth of individual peripheral cells is responsible for the observed periodic reduction in biofilm expansion.

Mentions: The synthesis of glutamine requires both glutamate and ammonium, therefore we investigated which of these substrates could be responsible for the observed glutamine limitation. Glutamate is provided in the media and is thus readily available to cells in the periphery of the biofilm. On the other hand, consumption of glutamate by peripheral cells is likely to limit its availability to cells in the biofilm interior (Fig. 2d). One may thus expect that oscillations in biofilm expansion could be due to periodic pausing of cell growth in the biofilm interior. Accordingly, we set out to establish whether interior or peripheral cells exhibited changes in growth. By tracking physical movement within the biofilm, we uncovered that only peripheral cells grow, and that oscillations in biofilm expansion therefore arise exclusively from periodic halting of peripheral cell growth (Fig. 2e, Supplementary Video 3, Extended Data Fig. 4a, and Methods: Data analysis). This finding was further confirmed by single cell resolution analysis that directly showed periodic reduction in the growth of peripheral cells (Extended Data Fig. 4b). This surprising pausing of cell growth in the periphery, despite unrestricted access to glutamate, suggests that glutamate cannot be the limiting substrate for glutamine synthesis. Consistent with this expectation, biofilm oscillations were not quenched by supplementation of the media with glutamate (Fig. 2f). Therefore, it is not glutamate, but ammonium that appears to be the limiting substrate for glutamine synthesis in the biofilm periphery.


Metabolic co-dependence gives rise to collective oscillations within biofilms.

Liu J, Prindle A, Humphries J, Gabalda-Sagarra M, Asally M, Lee DY, Ly S, Garcia-Ojalvo J, Süel GM - Nature (2015)

Measurements of cell growth within oscillating biofilms. a, (Top) Visual representation of the method through which difference movies are generated (Methods: Data Analysis). Growth is represented by white pixels, and lack of growth is indicated by black pixels. (Middle) Film strip and (bottom) growth area over time of an oscillating colony. Dashed lines show the position of each image on the time trace. Scale bar represents 100 µm. b, (Top left) schematic of a biofilm. (Top right) high magnification phase contrast image of biofilm periphery focused at the bottom layer of cells. (Bottom panel) time traces depicting elongation rates of single cells in gray. Highlighted in red is the single cell time trace for the cell outlined in red in the top right panel. The periodic slowdown of the growth of individual peripheral cells is responsible for the observed periodic reduction in biofilm expansion.
© Copyright Policy - permissions-link
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862617&req=5

Figure 8: Measurements of cell growth within oscillating biofilms. a, (Top) Visual representation of the method through which difference movies are generated (Methods: Data Analysis). Growth is represented by white pixels, and lack of growth is indicated by black pixels. (Middle) Film strip and (bottom) growth area over time of an oscillating colony. Dashed lines show the position of each image on the time trace. Scale bar represents 100 µm. b, (Top left) schematic of a biofilm. (Top right) high magnification phase contrast image of biofilm periphery focused at the bottom layer of cells. (Bottom panel) time traces depicting elongation rates of single cells in gray. Highlighted in red is the single cell time trace for the cell outlined in red in the top right panel. The periodic slowdown of the growth of individual peripheral cells is responsible for the observed periodic reduction in biofilm expansion.
Mentions: The synthesis of glutamine requires both glutamate and ammonium, therefore we investigated which of these substrates could be responsible for the observed glutamine limitation. Glutamate is provided in the media and is thus readily available to cells in the periphery of the biofilm. On the other hand, consumption of glutamate by peripheral cells is likely to limit its availability to cells in the biofilm interior (Fig. 2d). One may thus expect that oscillations in biofilm expansion could be due to periodic pausing of cell growth in the biofilm interior. Accordingly, we set out to establish whether interior or peripheral cells exhibited changes in growth. By tracking physical movement within the biofilm, we uncovered that only peripheral cells grow, and that oscillations in biofilm expansion therefore arise exclusively from periodic halting of peripheral cell growth (Fig. 2e, Supplementary Video 3, Extended Data Fig. 4a, and Methods: Data analysis). This finding was further confirmed by single cell resolution analysis that directly showed periodic reduction in the growth of peripheral cells (Extended Data Fig. 4b). This surprising pausing of cell growth in the periphery, despite unrestricted access to glutamate, suggests that glutamate cannot be the limiting substrate for glutamine synthesis. Consistent with this expectation, biofilm oscillations were not quenched by supplementation of the media with glutamate (Fig. 2f). Therefore, it is not glutamate, but ammonium that appears to be the limiting substrate for glutamine synthesis in the biofilm periphery.

Bottom Line: It remains unclear how these opposing interactions are resolved at the population level.We discover that this conflict between protection and starvation is resolved through emergence of long-range metabolic co-dependence between peripheral and interior cells.As a result, biofilm growth halts periodically, increasing nutrient availability for the sheltered interior cells.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, University of California San Diego, California 92093, USA.

ABSTRACT
Cells that reside within a community can cooperate and also compete with each other for resources. It remains unclear how these opposing interactions are resolved at the population level. Here we investigate such an internal conflict within a microbial (Bacillus subtilis) biofilm community: cells in the biofilm periphery not only protect interior cells from external attack but also starve them through nutrient consumption. We discover that this conflict between protection and starvation is resolved through emergence of long-range metabolic co-dependence between peripheral and interior cells. As a result, biofilm growth halts periodically, increasing nutrient availability for the sheltered interior cells. We show that this collective oscillation in biofilm growth benefits the community in the event of a chemical attack. These findings indicate that oscillations support population-level conflict resolution by coordinating competing metabolic demands in space and time, suggesting new strategies to control biofilm growth.

Show MeSH
Related in: MedlinePlus