Broken replication forks trigger heritable DNA breaks in the terminus of a circular chromosome

<p><u>(A) Circular map of the <i>E</i>. <i>coli</i> chromosome</u>: <i>oriC</i>, <i>dif</i> and <i>terD</i> to <i>terB</i> sites are indicated. Numbers refer to the chromosome coordinates (in kb) of MG1655. (<u>B) Linear map of the terminus region:</u> chromosome coordinates are shown increasing from left to right, as in the marker frequency panels (see Figure 1C for example), therefore in the opposite direction to the circular map. In addition to <i>dif</i> and <i>ter</i> sites, the positions of the <i>parS</i>_pMT1 sites used for microscopy experiments are indicated. (<u>C) MFA analysis of terminus DNA loss in the <i>recB</i> mutant</u>: sequence read frequencies of exponential phase cells normalized to the total number of reads were calculated for each strain. Ratios of normalized reads in isogenic wild-type and <i>recB</i> mutant are plotted against chromosomal coordinates (in kb). The profile ratio of the terminus region is enlarged and the profile of the corresponding entire chromosomes is shown in inset. Original normalized profiles used to calculate ratios are shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.s005" target="_blank">S1 Fig</a>. The position of <i>dif</i> is indicated by a red arrow. The <i>ter</i> sites that arrest clockwise forks (<i>terC</i>, <i>terB</i>, green arrow) and counter-clockwise forks (<i>terA</i>, <i>terD</i>, blue arrow) are shown. <u>(D) Schematic representation of focus loss in the <i>recB</i> mutant:</u> Time-lapse microscopy experiments showed that loss of a focus in the <i>recB</i> mutant occurs concomitantly with cell division in one of two daughter cells, and that the cell that keeps the focus then generates a focus-less cell at each generation. The percentage of initial events was calculated as the percentage of cell divisions that generate a focus-less cell, not counting the following generations. In this schematic representation, two initial events occurred (generations #2 and #7) out of 9 generations, and focus loss at generation #2 is heritable. Panels shown in this figure were previously published in [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.ref019" target="_blank">19</a>] and are reproduced here to introduce the phenomenon.</p

Mapping the vulnerability for evacuation of the Campi Flegrei territorial system in case of a volcanic unrest

Over the past few decades the Campi Flegrei territorial system was interested by intense urban expansion overlooking the volcanic risk. In this active volcanic area, where a short period evacuation could be necessary, the emergency management cannot be based solely on the hazard related information, but the territorial and social features must be as well taken into account. In this framework, the main purpose of this research is to point out the seriousness of the present setting of Campi Flegrei territorial system in case an evacuation would become necessary. Following the concept of regional evacuation, the zone to be involved in emergency planning was identified as the whole of the area threatened by the volcanic events occurred in the last 10 ka. Inside this area the spatial relation between the residents distribution and the outflows of routes, railway stations and harbours, necessary to leave the dangerous area, was investigated. A spatial relational GIS-based procedure was used to draw the territorial system vulnerability map for evacuation, depicting the zones with different capability to support the evacuation of residents in case of renewal of volcanic activity. Basing on the concept that people could leave the dangerous area by the means of transport supplied by Civil Protection, and using the threshold value of over-crowding of 0,70 people/ m2, we identified the collection points for residents to be immediately evacuated in case of volcanic unrest, and five microzones displaying different capability to cope with an emergency phase