article published yes Veronika Bierbaum author 3FD04378-F248-11E8-B48F-1D18A9856A87 Stefan Klumpp author MiSi department In growing cells, protein synthesis and cell growth are typically not synchronous, and, thus, protein concentrations vary over the cell division cycle. We have developed a theoretical description of genetic regulatory systems in bacteria that explicitly considers the cell division cycle to investigate its impact on gene expression. We calculate the cell-to-cell variations arising from cells being at different stages in the division cycle for unregulated genes and for basic regulatory mechanisms. These variations contribute to the extrinsic noise observed in single-cell experiments, and are most significant for proteins with short lifetimes. Negative autoregulation buffers against variation of protein concentration over the division cycle, but the effect is found to be relatively weak. Stronger buffering is achieved by an increased protein lifetime. Positive autoregulation can strongly amplify such variation if the parameters are set to values that lead to resonance-like behaviour. For cooperative positive autoregulation, the concentration variation over the division cycle diminishes the parameter region of bistability and modulates the switching times between the two stable states. The same effects are seen for a two-gene mutual-repression toggle switch. By contrast, an oscillatory circuit, the repressilator, is only weakly affected by the division cycle. IOP Publishing2015 eng 00036818630000910.1088/1478-3975/12/6/066003 126 Bierbaum, Veronika, and Stefan Klumpp. “Impact of the Cell Division Cycle on Gene Circuits.” <i>Physical Biology</i>, vol. 12, no. 6, 066003, IOP Publishing, 2015, doi:<a href="https://doi.org/10.1088/1478-3975/12/6/066003">10.1088/1478-3975/12/6/066003</a>. Bierbaum V, Klumpp S. Impact of the cell division cycle on gene circuits. <i>Physical Biology</i>. 2015;12(6). doi:<a href="https://doi.org/10.1088/1478-3975/12/6/066003">10.1088/1478-3975/12/6/066003</a> Bierbaum, Veronika, and Stefan Klumpp. “Impact of the Cell Division Cycle on Gene Circuits.” <i>Physical Biology</i>. IOP Publishing, 2015. <a href="https://doi.org/10.1088/1478-3975/12/6/066003">https://doi.org/10.1088/1478-3975/12/6/066003</a>. V. Bierbaum and S. Klumpp, “Impact of the cell division cycle on gene circuits,” <i>Physical Biology</i>, vol. 12, no. 6. IOP Publishing, 2015. Bierbaum V, Klumpp S. 2015. Impact of the cell division cycle on gene circuits. Physical Biology. 12(6), 066003. Bierbaum, V., &#38; Klumpp, S. (2015). Impact of the cell division cycle on gene circuits. <i>Physical Biology</i>. IOP Publishing. <a href="https://doi.org/10.1088/1478-3975/12/6/066003">https://doi.org/10.1088/1478-3975/12/6/066003</a> V. Bierbaum, S. Klumpp, Physical Biology 12 (2015). 15302018-12-11T11:52:33Z2025-09-23T09:19:53Z