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Directed evolution of cell size in Escherichia coli.

Yoshida M, Tsuru S, Hirata N, Seno S, Matsuda H, Ying BW, Yomo T - BMC Evol. Biol. (2014)

Bottom Line: This selection-propagation cycle was repeated, and significant changes in cell size were detected within 400 generations.In conclusion, bacterial cell size could evolve, through a few mutations, without growth reduction.The size evolution without growth reduction suggests a rapid evolutionary change to diverse cell sizes in bacterial survival strategies.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka, 565-0871, Japan. maaaaaari8852@gmail.com.

ABSTRACT

Background: In bacteria, cell size affects chromosome replication, the assembly of division machinery, cell wall synthesis, membrane synthesis and ultimately growth rate. In addition, cell size can also be a target for Darwinian evolution for protection from predators. This strong coupling of cell size and growth, however, could lead to the introduction of growth defects after size evolution. An important question remains: can bacterial cell size change and/or evolve without imposing a growth burden?

Results: The directed evolution of particular cell sizes, without a growth burden, was tested with a laboratory Escherichia coli strain. Cells of defined size ranges were collected by a cell sorter and were subsequently cultured. This selection-propagation cycle was repeated, and significant changes in cell size were detected within 400 generations. In addition, the width of the size distribution was altered. The changes in cell size were unaccompanied by a growth burden. Whole genome sequencing revealed that only a few mutations in genes related to membrane synthesis conferred the size evolution.

Conclusions: In conclusion, bacterial cell size could evolve, through a few mutations, without growth reduction. The size evolution without growth reduction suggests a rapid evolutionary change to diverse cell sizes in bacterial survival strategies.

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Related in: MedlinePlus

Cell size distributions of twoE. colistrains. (A) Phase-contrast images of two E. coli strains (left, MG1655, and right, BSKY). The scale bar represents 10 μm. (B) Cell size distributions obtained by microscopy. The solid and dashed lines indicate BSKY and MDS42, respectively. The inset represents the corresponding cell size distributions obtained by flow cytometry.
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Fig1: Cell size distributions of twoE. colistrains. (A) Phase-contrast images of two E. coli strains (left, MG1655, and right, BSKY). The scale bar represents 10 μm. (B) Cell size distributions obtained by microscopy. The solid and dashed lines indicate BSKY and MDS42, respectively. The inset represents the corresponding cell size distributions obtained by flow cytometry.

Mentions: We employed a GFP-integrated derivative of E. coli DH1, called BSKY, as an ancestral clonal population. DH1, including BSKY, is large, filamentous and rod-shaped and is more heterogeneous in size than the wild-type strain, MG1655 (Figure 1). This property implies that BSKY has a capacity to evolve to smaller sizes by reducing the filamentous fraction in response to the appropriate selections without facing physical limitations. Therefore, we considered this strain an appropriate ancestor to test whether the evolution to smaller size is accompanied with growth changes. We used a fluorescence activated cell sorter (FACS) to sort the bacterial cells according to their relative size, based on the forward scatter value (FSC) in flow cytometry (Figure 1B inset). The FSC basically reflects the length, or the longest diameter, in rod-shaped bacteria, and agrees well with microscopic observation [18]. As a result, the larger and/or broader size distributions were also captured consistently in flow cytometry and microscopy. We employed mean values and standard deviations on a logarithmic scale to characterize these size distributions.Figure 1


Directed evolution of cell size in Escherichia coli.

Yoshida M, Tsuru S, Hirata N, Seno S, Matsuda H, Ying BW, Yomo T - BMC Evol. Biol. (2014)

Cell size distributions of twoE. colistrains. (A) Phase-contrast images of two E. coli strains (left, MG1655, and right, BSKY). The scale bar represents 10 μm. (B) Cell size distributions obtained by microscopy. The solid and dashed lines indicate BSKY and MDS42, respectively. The inset represents the corresponding cell size distributions obtained by flow cytometry.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4279887&req=5

Fig1: Cell size distributions of twoE. colistrains. (A) Phase-contrast images of two E. coli strains (left, MG1655, and right, BSKY). The scale bar represents 10 μm. (B) Cell size distributions obtained by microscopy. The solid and dashed lines indicate BSKY and MDS42, respectively. The inset represents the corresponding cell size distributions obtained by flow cytometry.
Mentions: We employed a GFP-integrated derivative of E. coli DH1, called BSKY, as an ancestral clonal population. DH1, including BSKY, is large, filamentous and rod-shaped and is more heterogeneous in size than the wild-type strain, MG1655 (Figure 1). This property implies that BSKY has a capacity to evolve to smaller sizes by reducing the filamentous fraction in response to the appropriate selections without facing physical limitations. Therefore, we considered this strain an appropriate ancestor to test whether the evolution to smaller size is accompanied with growth changes. We used a fluorescence activated cell sorter (FACS) to sort the bacterial cells according to their relative size, based on the forward scatter value (FSC) in flow cytometry (Figure 1B inset). The FSC basically reflects the length, or the longest diameter, in rod-shaped bacteria, and agrees well with microscopic observation [18]. As a result, the larger and/or broader size distributions were also captured consistently in flow cytometry and microscopy. We employed mean values and standard deviations on a logarithmic scale to characterize these size distributions.Figure 1

Bottom Line: This selection-propagation cycle was repeated, and significant changes in cell size were detected within 400 generations.In conclusion, bacterial cell size could evolve, through a few mutations, without growth reduction.The size evolution without growth reduction suggests a rapid evolutionary change to diverse cell sizes in bacterial survival strategies.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka, 565-0871, Japan. maaaaaari8852@gmail.com.

ABSTRACT

Background: In bacteria, cell size affects chromosome replication, the assembly of division machinery, cell wall synthesis, membrane synthesis and ultimately growth rate. In addition, cell size can also be a target for Darwinian evolution for protection from predators. This strong coupling of cell size and growth, however, could lead to the introduction of growth defects after size evolution. An important question remains: can bacterial cell size change and/or evolve without imposing a growth burden?

Results: The directed evolution of particular cell sizes, without a growth burden, was tested with a laboratory Escherichia coli strain. Cells of defined size ranges were collected by a cell sorter and were subsequently cultured. This selection-propagation cycle was repeated, and significant changes in cell size were detected within 400 generations. In addition, the width of the size distribution was altered. The changes in cell size were unaccompanied by a growth burden. Whole genome sequencing revealed that only a few mutations in genes related to membrane synthesis conferred the size evolution.

Conclusions: In conclusion, bacterial cell size could evolve, through a few mutations, without growth reduction. The size evolution without growth reduction suggests a rapid evolutionary change to diverse cell sizes in bacterial survival strategies.

Show MeSH
Related in: MedlinePlus