## 1 Introduction  
In living cells, replication fork progression is frequently hindered by obstacles in and on the DNA template [1; 2; 3; 4]. Cells may use several strategies when DNA replication is challenged by this stress: replication forks stall, DNA polymerases uncouple, lesions can be simply skipped by the replisome forming single-stranded DNA (ssDNA) gaps, or the stalled fork is pushed backwards to convert it into a Holliday junction (HJ)-like structure by allowing the pairing of the two nascent strands and rewinding of the parental strands (fork reversal, known also as fork regression) [5; 6; 7; 8; 9]. Nevertheless, in _Escherichia coli_, fork reversal appears to be a less relevant response to DNA damage, and is infrequent in wild-type (_wt_) cells, because reversed forks are susceptible to nucleolytic degradation of the regressed nascent DNA arms. In fact, RecBCD (counterpart of _Bacillus subtilis_ AddAB) prevents or removes reversed fork structures, and in the \(\Delta recBCD\) context, the reversed forks are processed by the RuvAB translocase and cleaved by the RuvC (counterpart of _B. subtilis_ RecU) HJ resolvase, leading to fork breakage and one-ended double-strand breaks (DSBs) [7; 10; 8]. In sharp contrast, in mammalian cells [11] or during the early stage of _B. subtilis_ spore revival [12; 13], dedicated mechanisms are actively involved in the formation and integrity of reversed forks. Therefore, the analysis of the repair functions active in reviving _B. subtilis_ spores gives clues of the proteins that contribute to genome integrity after fork stalling, because breakage of a reversed fork should be pathological during phases where only one genome copy is available, and cells should prevent it (unless stated otherwise, indicated genes and products are of _B. subtilis_ origin). When the DNA of an inert mature haploid spore is damaged by ionizing radiation, and then the spores are synchronously revived under unperturbed conditions, spores lacking both AddAB and Rec] exonucleases are as capable of repairing the damage as the \(wt\) control [12], showing that long-range end-resection functions play a minor role in removing a replicative stress. Indeed, these proteins are synthesized after initiation of spore replication and prior to cell elongation [14; 15]. By contrast, spores required the recombinase RecA, its mediators and modulators, the branch migration translocases (RuvAB, RecG), the HJ resolvase RecU, and the DNA damage checkpoint sensor DisA for replication fork rescue [12; 13]. We can envision that during the first replication cycle of those reviving spores, in the absence of an intact homologous template and end-resection functions, the fork may be reversed to remove a replicative stress. This way, the lesion is placed on a double-stranded (ds) configuration to permit its removal by means of base- and nucleotide-excision repair. Then, the regressed nascent complementary DNA arms can potentially allow for the bypass of template DNA obstructions by error-prone and error-free DNA damage tolerance (DDT) sub-pathways that contribute to bypass or circumvent the lesion. Nevertheless, fork remodeling could be controlled by a poorly characterized function to avoid the formation of highly detrimental DSBs. In vivo analyses showed that DisA is a DNA sensor protein found in the Firmicutes and Actinobacteria phyla, among others [16]. DisA forms a focus that moves rapidly along the chromosome scanning for \"perturbations\" but pauses its movement upon DNA damage and delays entry into sporulation until the offending lesion is removed [17]. DisA still pauses in the absence of long-range end resection (\(\Delta\)_addAB ArcJ_ cells) [18], but it does not pause in the absence of RecO and RecA. This suggests that DisA pauses at a DNA structure formed after RecO and RecA engagement at a site of replicative stress, so that the primary signal recognized by DisA is a lesion-containing gap or a branched intermediate rather than DNA ends or DSBs.