Limits...
Small regulatory RNA-induced growth rate heterogeneity of Bacillus subtilis.

Mars RA, Nicolas P, Ciccolini M, Reilman E, Reder A, Schaffer M, Mäder U, Völker U, van Dijl JM, Denham EL - PLoS Genet. (2015)

Bottom Line: This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation.Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase.Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.

ABSTRACT
Isogenic bacterial populations can consist of cells displaying heterogeneous physiological traits. Small regulatory RNAs (sRNAs) could affect this heterogeneity since they act by fine-tuning mRNA or protein levels to coordinate the appropriate cellular behavior. Here we show that the sRNA RnaC/S1022 from the Gram-positive bacterium Bacillus subtilis can suppress exponential growth by modulation of the transcriptional regulator AbrB. Specifically, the post-transcriptional abrB-RnaC/S1022 interaction allows B. subtilis to increase the cell-to-cell variation in AbrB protein levels, despite strong negative autoregulation of the abrB promoter. This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation. Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase. Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions.

Show MeSH

Related in: MedlinePlus

RnaC/S1022-induced variation in AbrB-GFP levels leads to heterogeneity in growth rates.A) Tracing of growth and AbrB-GFP levels of 71 individual micro-colonies from Δspo0A AbrB-GFP strains with either zero or two chromosomal copies of RnaC/S1022. Data originates from three independent experiments. Cell growth is expressed as the cell length (Feret’s diameter) increase per hour as determined in the first 20 min after spotting of the cells onto agarose slides. The plotted AbrB-GFP level is the average of fluorescence in the first and second picture. B) Distribution of AbrB-GFP start levels for both strains. Note that two genomic RnaC/S1022 copies lead to a wider distribution of AbrB-GFP levels. C) Montage of the two adjacent dividing cells from the S1 Movie. The white outline marks the contours of the cell. The positions of these cells in panel A are marked with an O. Individual cells were cropped for illustration purposes only.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4366234&req=5

pgen.1005046.g008: RnaC/S1022-induced variation in AbrB-GFP levels leads to heterogeneity in growth rates.A) Tracing of growth and AbrB-GFP levels of 71 individual micro-colonies from Δspo0A AbrB-GFP strains with either zero or two chromosomal copies of RnaC/S1022. Data originates from three independent experiments. Cell growth is expressed as the cell length (Feret’s diameter) increase per hour as determined in the first 20 min after spotting of the cells onto agarose slides. The plotted AbrB-GFP level is the average of fluorescence in the first and second picture. B) Distribution of AbrB-GFP start levels for both strains. Note that two genomic RnaC/S1022 copies lead to a wider distribution of AbrB-GFP levels. C) Montage of the two adjacent dividing cells from the S1 Movie. The white outline marks the contours of the cell. The positions of these cells in panel A are marked with an O. Individual cells were cropped for illustration purposes only.

Mentions: We next aimed to unravel the effect of sRNA-induced AbrB heterogeneity on growth. This requires the tracking of cells with low and high AbrB-GFP levels over time. To do this, we performed a live imaging experiment with the Δspo0A AbrB-GFP strain either containing zero sRNA copies due to the ΔRnaC/S1022 mutation, or two genomic copies due to the insertion of an additional RnaC/S1022 copy in amyE. The Δspo0A background was used to elevate AbrB-GFP levels and thereby to facilitate fluorescence measurements. Cells were pre-cultured in M9G as was done for the FC measurements and applied to agarose pads (at OD600 ∼0.15) essentially as was described by Piersma et al. [52]. From these experiments, and consistent with FC data in Fig. 5, it was apparent that there was a larger variation in AbrB-GFP levels in the strain with two genomic RnaC/S1022 copies, compared to the strain lacking RnaC/S1022 (Fig. 8B; S1 Movie). In addition, this variation in AbrB-GFP levels was correlated to the variation in growth rates (quantified as the specific cell length increase) observed during the first 20 min of each live imaging run (Fig. 8A). We excluded the possibility that this growth rate difference was dependent on the position on, or quality of the slide. Instead, it was solely linked to the cellular level of AbrB-GFP (Fig. 8C; S1 Movie).


Small regulatory RNA-induced growth rate heterogeneity of Bacillus subtilis.

Mars RA, Nicolas P, Ciccolini M, Reilman E, Reder A, Schaffer M, Mäder U, Völker U, van Dijl JM, Denham EL - PLoS Genet. (2015)

RnaC/S1022-induced variation in AbrB-GFP levels leads to heterogeneity in growth rates.A) Tracing of growth and AbrB-GFP levels of 71 individual micro-colonies from Δspo0A AbrB-GFP strains with either zero or two chromosomal copies of RnaC/S1022. Data originates from three independent experiments. Cell growth is expressed as the cell length (Feret’s diameter) increase per hour as determined in the first 20 min after spotting of the cells onto agarose slides. The plotted AbrB-GFP level is the average of fluorescence in the first and second picture. B) Distribution of AbrB-GFP start levels for both strains. Note that two genomic RnaC/S1022 copies lead to a wider distribution of AbrB-GFP levels. C) Montage of the two adjacent dividing cells from the S1 Movie. The white outline marks the contours of the cell. The positions of these cells in panel A are marked with an O. Individual cells were cropped for illustration purposes only.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4366234&req=5

pgen.1005046.g008: RnaC/S1022-induced variation in AbrB-GFP levels leads to heterogeneity in growth rates.A) Tracing of growth and AbrB-GFP levels of 71 individual micro-colonies from Δspo0A AbrB-GFP strains with either zero or two chromosomal copies of RnaC/S1022. Data originates from three independent experiments. Cell growth is expressed as the cell length (Feret’s diameter) increase per hour as determined in the first 20 min after spotting of the cells onto agarose slides. The plotted AbrB-GFP level is the average of fluorescence in the first and second picture. B) Distribution of AbrB-GFP start levels for both strains. Note that two genomic RnaC/S1022 copies lead to a wider distribution of AbrB-GFP levels. C) Montage of the two adjacent dividing cells from the S1 Movie. The white outline marks the contours of the cell. The positions of these cells in panel A are marked with an O. Individual cells were cropped for illustration purposes only.
Mentions: We next aimed to unravel the effect of sRNA-induced AbrB heterogeneity on growth. This requires the tracking of cells with low and high AbrB-GFP levels over time. To do this, we performed a live imaging experiment with the Δspo0A AbrB-GFP strain either containing zero sRNA copies due to the ΔRnaC/S1022 mutation, or two genomic copies due to the insertion of an additional RnaC/S1022 copy in amyE. The Δspo0A background was used to elevate AbrB-GFP levels and thereby to facilitate fluorescence measurements. Cells were pre-cultured in M9G as was done for the FC measurements and applied to agarose pads (at OD600 ∼0.15) essentially as was described by Piersma et al. [52]. From these experiments, and consistent with FC data in Fig. 5, it was apparent that there was a larger variation in AbrB-GFP levels in the strain with two genomic RnaC/S1022 copies, compared to the strain lacking RnaC/S1022 (Fig. 8B; S1 Movie). In addition, this variation in AbrB-GFP levels was correlated to the variation in growth rates (quantified as the specific cell length increase) observed during the first 20 min of each live imaging run (Fig. 8A). We excluded the possibility that this growth rate difference was dependent on the position on, or quality of the slide. Instead, it was solely linked to the cellular level of AbrB-GFP (Fig. 8C; S1 Movie).

Bottom Line: This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation.Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase.Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.

ABSTRACT
Isogenic bacterial populations can consist of cells displaying heterogeneous physiological traits. Small regulatory RNAs (sRNAs) could affect this heterogeneity since they act by fine-tuning mRNA or protein levels to coordinate the appropriate cellular behavior. Here we show that the sRNA RnaC/S1022 from the Gram-positive bacterium Bacillus subtilis can suppress exponential growth by modulation of the transcriptional regulator AbrB. Specifically, the post-transcriptional abrB-RnaC/S1022 interaction allows B. subtilis to increase the cell-to-cell variation in AbrB protein levels, despite strong negative autoregulation of the abrB promoter. This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation. Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase. Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions.

Show MeSH
Related in: MedlinePlus