Bacillus subtilis RarA acts as a positive RecA accessory protein

Ubiquitous RarA AAA+ ATPases play crucial roles in the cellular response to blocked replication forks in pro- and eukaryotes. Here, we provide evidence that absence of RarA reduced the viability of ΔrecA, ΔrecO, and recF15 cells during unperturbed growth. The rarA gene was epistatic to recO and recF genes in response to H2O2- or MMS-induced DNA damage. Conversely, the inactivation of rarA partially suppressed the HR defect of mutants lacking end-resection (ΔaddAB, ΔrecJ, ΔrecQ, ΔrecS) or branch migration (ΔruvAB, ΔrecG, ΔradA) activity. RarA contributes to RecA thread formation, that are thought to be the active forms of RecA during homology search. The absence of RarA reduced RecA accumulation, and the formation of visible RecA threads in vivo upon DNA damage. When ΔrarA was combined with mutations in genuine RecA accessory genes, RecA accumulation was further reduced in ΔrarA ΔrecU and ΔrarA ΔrecX double mutant cells, and was blocked in ΔrarA recF15 cells. These results suggest that RarA contributes to the assembly of RecA nucleoprotein filaments onto single-stranded DNA, and possibly antagonizes RecA filament disassembly

Prodromal symptoms and the duration of untreated psychosis in first episode of psychosis patients: what differences are there between early vs. adult onset and between schizophrenia vs. bipolar disorder?

To assess the role of age (early onset psychosis-EOP < 18 years vs. adult onset psychosis-AOP) and diagnosis (schizophrenia spectrum disorders-SSD vs. bipolar disorders-BD) on the duration of untreated psychosis (DUP) and prodromal symptoms in a sample of patients with a first episode of psychosis. 331 patients with a first episode of psychosis (7–35 years old) were recruited and 174 (52.6%) diagnosed with SSD or BD at one-year follow-up through a multicenter longitudinal study. The Symptom Onset in Schizophrenia (SOS) inventory, the Positive and Negative Syndrome Scale and the structured clinical interviews for DSM-IV diagnoses were administered. Generalized linear models compared the main effects and group interaction. 273 AOP (25.2 ± 5.1 years; 66.5% male) and 58 EOP patients (15.5 ± 1.8 years; 70.7% male) were included. EOP patients had significantly more prodromal symptoms with a higher frequency of trouble with thinking, avolition and hallucinations than AOP patients, and significantly different median DUP (91 [33–177] vs. 58 [21–140] days; Z = − 2.006, p = 0.045). This was also significantly longer in SSD vs. BD patients (90 [31–155] vs. 30 [7–66] days; Z = − 2.916, p = 0.004) who, moreover had different profiles of prodromal symptoms. When assessing the interaction between age at onset (EOP/AOP) and type of diagnosis (SSD/BD), avolition was significantly higher (Wald statistic = 3.945; p = 0.047), in AOP patients with SSD compared to AOP BD patients (p = 0.004). Awareness of differences in length of DUP and prodromal symptoms in EOP vs. AOP and SSD vs. BD patients could help improve the early detection of psychosis among minors

The ζ Toxin Induces a Set of Protective Responses and Dormancy

The ζε module consists of a labile antitoxin protein, ε, which in dimer form (ε2) interferes with the action of the long-living monomeric ζ phosphotransferase toxin through protein complex formation. Toxin ζ, which inhibits cell wall biosynthesis and may be bactericide in nature, at or near physiological concentrations induces reversible cessation of Bacillus subtilis proliferation (protective dormancy) by targeting essential metabolic functions followed by propidium iodide (PI) staining in a fraction (20–30%) of the population and selects a subpopulation of cells that exhibit non-inheritable tolerance (1–5×10−5). Early after induction ζ toxin alters the expression of ∼78 genes, with the up-regulation of relA among them. RelA contributes to enforce toxin-induced dormancy. At later times, free active ζ decreases synthesis of macromolecules and releases intracellular K+. We propose that ζ toxin induces reversible protective dormancy and permeation to PI, and expression of ε2 antitoxin reverses these effects. At later times, toxin expression is followed by death of a small fraction (∼10%) of PI stained cells that exited earlier or did not enter into the dormant state. Recovery from stress leads to de novo synthesis of ε2 antitoxin, which blocks ATP binding by ζ toxin, thereby inhibiting its phosphotransferase activity

Toxin ζ Reversible Induces Dormancy and Reduces the UDP-N-Acetylglucosamine Pool as One of the Protective Responses to Cope with Stress

Toxins of the ζ/PezT family, found in the genome of major human pathogens, phosphorylate the peptidoglycan precursor uridine diphosphate-N-acetylglucosamine (UNAG) leading to unreactive UNAG-3P. Transient over-expression of a PezT variant impairs cell wall biosynthesis and triggers autolysis in Escherichia coli. Conversely, physiological levels of ζ reversibly induce dormancy produce a sub-fraction of membrane-compromised cells, and a minor subpopulation of Bacillus subtilis cells become tolerant of toxin action. We report here that purified ζ is a strong UNAG-dependent ATPase, being GTP a lower competitor. In vitro, ζ toxin phosphorylates a fraction of UNAG. In vivo, ζ-mediated inactivation of UNAG by phosphorylation does not deplete the active UNAG pool, because expression of the toxin enhances the efficacy of genuine cell wall inhibitors (fosfomycin, vancomycin or ampicillin). Transient ζ expression together with fosfomycin treatment halt cell proliferation, but ε2 antitoxin expression facilitates the exit of ζ-induced dormancy, suggesting that there is sufficient UNAG for growth. We propose that ζ induces diverse cellular responses to cope with stress, being the reduction of the UNAG pool one among them. If the action of ζ is not inhibited, e.g., by de novo ε2 antitoxin synthesis, the toxin markedly enhances the efficacy of antimicrobial treatment without massive autolysis in Firmicutes

Recombination proteins differently control the acquisition of homeologous DNA during Bacillus subtilis natural chromosomal transformation.

Natural chromosomal transformation (CT) plays a major role in prokaryote evolution, yet factors that govern the integration of DNA from related species remain poorly understood. We show that in naturally competent Bacillus subtilis cells the acquisition of homeologous sequences is governed by sequence divergence (SD). Integration initiates in a minimal efficient processing segment via homology‐directed CT, and its frequency decreases log‐linearly with increased SD up to 15%. Beyond this and up to 23% SD the interspecies boundaries prevail, the CT frequency marginally decreases, and short (<10‐nucleotides) segments are integrated via homology‐facilitated micro‐homologous integration. Both mechanisms are RecA dependent. We identify the other recombination proteins required for the acquisition of homeologous DNA. The absence of AddAB, RecF, RecO, RuvAB or RecU, crucial for repair‐by‐recombination, did not affect CT. However, dprA, radA, recJ, recX or recD2 inactivation strongly decreased intraspecies and interspecies CT. Interspecies CT was not detected beyond ~8% SD in ΔdprA, ~10% in ΔrecJ, ΔradA, ΔrecX and ~14% in ΔrecD2 cells. We propose that DprA, RecX, RadA/Sms, RecJ and RecD2 accessory proteins are important for the generation of genetic diversity. Together with RecA, they facilitate gene acquisition from bacteria of related species