Evolved sequence features within the intrinsically disordered tail influence FtsZ assembly and bacterial cell division

Megan C. Cohan; Ammon E. Posey; Steven J. Grigsby; Anuradha Mittal; Alex S. Holehouse; Paul J. Buske; Petra A. Levin; Rohit V. Pappu

To quantify the robustness / disruption of Z-ring formation, we measured the L/R ratio, which describes the ratio of the average length of the cell to the number of Z-rings observed (Buske and Levin, 2013) . This is a measure of the fitness and robustness of cell division in rodshaped bacteria. The L/R ratio is 7.2 ± 1.2 for cells expressing WT FtsZ. Compromised fitness is indicated by L/R ratios that are larger than the WT. The L/R ratio is 5.9 ± 1.1, 6.6 ± 1.0, and 5.8 ± 0.9 for cells expressing variants CTLV2, CTLV3, and CTLV4, respectively ( Figure 3C ). These measurements suggest robust Z-ring formation and division for cells expressing FtsZ variants with CTT κ values between 0.18 and 0.40. In contrast, the L/R ratio is 18.8 ± 1.6, 57.5 ± 12.5, and 117.3 ± 27.6 for cells expressing variants CTLV1 (CTT κ=0.15), CTLV5 (CTT κ=0.46), and CTLV6 (CTT κ=0.72), respectively.