The bin size was 2 min. Additional data are shown in Tables 1 and 2. Effect of allelic variation in holin sequence

It has long been known that different holin alleles show different lysis times [37, 46, 47]. However, it is not clear to what extent allelic differences in holin protein would affect the lysis timing of individual cells. To gain further insight, we determined the MLTs (mean lysis times) and SDs (standard deviations) of lysis time for 14 isogenic l lysogens differing in their S holin sequences (see APPENDIX B for our rationale for using SD as the measure for lysis time stochasticity). The directly observed MLTs (Table 1) were longer than those reported previously [46]. This discrepancy was mainly due to the fact that, in previous work, lysis time was defined by the time selleck compound point when the turbidity of the lysogen mTOR inhibitor culture began to decline, whereas in our current measurement, it

was the mean of all individual lysis times observed for a particular phage strain. Figure 3A revealed a significant positive relationship between MLT and SD (F [1,12] = 8.42, p = 0.0133). However, we did not observe a significant relationship between MLT and another commonly used measure of stochasticity, the coefficient of variation (CV, defined as SD/MLT; [15, 25, 48, 49]) (F [1,12] = 1.50, p = 0.2445), indicating a proportional increase of the SD with the MLT. Figure 3A also reveals a relatively scattered relationship between the MLTs and the SDs (adjusted R 2 = 0.363), with several instances in which strains with similar MLTs are accompanied by very different SDs. For example, the mean lysis times for IN56 and IN71 were 65.1 and 68.8 min, but the SDs were 3.2 and 7.7 min, respectively. Apparently the observed

positive relationship is only a general trend, not an absolute. The scattering of the plot also suggests that different CHIR-99021 manufacturer missense mutations in the holin sequence can influence MLT and SD somewhat independently. Figure 3 Factors influencing λ lysis time stochasticity. (A) Effect of allelic variation in holin proteins on mean lysis times (MLTs) and standard deviations (SDs). (B) Effect of λ’s late promoter p R ‘ activity [50] on MLTs, SDs and CVs (coefficients of variation). Solid curve is SD = 3.05 (72.73 + P)/P, where P was the p R ‘ activity. (C) Effects of p R ‘ activity and host growth rate on lysis time stochasticity. The regression line was obtained by fitting all data points from the late promoter activity (filled diamonds) and lysogen growth rate (open squares) find more treatments, except for the datum with the longest MLT and largest SD (from SYP028 in Table 2). (D) Effect of lysogen growth rate on MLT, SD, and CV. The fitted solid line shows the relationship between the growth rate and SD. All data are from Tables 1 and 2. Symbols: open circles, MLT; close circles, SD; closed triangles, CV.