Infections caused by
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Maintenance of DNA integrity is essential to all forms of life. DNA damage generated by reaction with genotoxic chemicals results in deleterious mutations, genome instability, and cell death. Pathogenic bacteria encounter several genotoxic agents during infection. In keeping with this, the loss of DNA repair networks results in virulence attenuation in several bacterial species. Interstrand DNA crosslinks (ICLs) are a type of DNA lesion formed by covalent linkage of opposing DNA strands and are particularly toxic as they interfere with replication and transcription. Bacteria have evolved specialized DNA glycosylases that unhook ICLs, thereby initiating their repair. In this study, we describe AlkX, a DNA glycosylase encoded by the multidrug resistant pathogen
- NSF-PAR ID:
- 10537899
- Publisher / Repository:
- National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 121
- Issue:
- 27
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Acinetobacter baumannii , a Gram‐negative opportunistic pathogen, are difficult to eradicate due to the bacterium's propensity to quickly gain antibiotic resistances and form biofilms, a protective bacterial multicellular community. TheA. baumannii DNA damage response (DDR) mediates the antibiotic resistance acquisition and regulates RecA in an atypical fashion; both RecALowand RecAHighcell types are formed in response to DNA damage. The findings of this study demonstrate that the levels of RecA can influence formation and dispersal of biofilms. RecA loss results in surface attachment and prominent biofilms, while elevated RecA leads to diminished attachment and dispersal. These findings suggest that the challenge to treatA. baumannii infections may be explained by the induction of the DDR, common during infection, as well as the delicate balance between maintaining biofilms in low RecA cells and promoting mutagenesis and dispersal in high RecA cells. This study underscores the importance of understanding the fundamental biology of bacteria to develop more effective treatments for infections. -
Summary All organisms possess DNA repair pathways that are used to maintain the integrity of their genetic material. Although many DNA repair pathways are well understood, new pathways continue to be discovered. Here, we report an antibiotic specific DNA repair pathway in
Bacillus subtilis that is composed of a previously uncharacterized helicase (mrfA ) and exonuclease (mrfB ). Deletion ofmrfA andmrfB results in sensitivity to the DNA damaging agent mitomycin C, but not to any other type of DNA damage tested. We show that MrfAB function independent of canonical nucleotide excision repair, forming a novel excision repair pathway. We demonstrate that MrfB is a metal‐dependent exonuclease and that the N‐terminus of MrfB is required for interaction with MrfA. We determined that MrfAB failed to unhook interstrand cross‐linksin vivo , suggesting that MrfAB are specific to the monoadduct or the intrastrand cross‐link. A phylogenetic analysis uncovered MrfAB homologs in diverse bacterial phyla, and cross‐complementation indicates that MrfAB function is conserved in closely related species.B. subtilis is a soil dwelling organism and mitomycin C is a natural antibiotic produced by the soil bacteriumStreptomyces lavendulae . The specificity of MrfAB suggests that these proteins are an adaptation to environments with mitomycin producing bacteria. -
Abstract Unrepaired DNA damage encountered by the cellular replication machinery can stall DNA replication, ultimately leading to cell death. In the DNA damage tolerance pathway translesion synthesis (TLS), replication stalling is alleviated by the recruitment of specialized polymerases to synthesize short stretches of DNA near a lesion. Although TLS promotes cell survival, most TLS polymerases are low-fidelity and must be tightly regulated to avoid harmful mutagenesis. The gram-negative bacterium Escherichia coli has served as the model organism for studies of the molecular mechanisms of bacterial TLS. However, it is poorly understood whether these same mechanisms apply to other bacteria. Here, we use in vivo single-molecule fluorescence microscopy to investigate the TLS polymerase Pol Y1 in the model gram-positive bacterium Bacillus subtilis. We find significant differences in the localization and dynamics of Pol Y1 in comparison to its E. coli homolog, Pol IV. Notably, Pol Y1 is constitutively enriched at or near sites of replication in the absence of DNA damage through interactions with the DnaN clamp; in contrast, Pol IV has been shown to be selectively enriched only upon replication stalling. These results suggest key differences in the roles and mechanisms of regulation of TLS polymerases across different bacterial species.
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