Influence of Redox Imbalances on the Transposition of Insertion Sequences in Deinococcus geothermalis

Abstract

The transposition of insertion sequence elements was evaluated among different Deinococcus geothermalis lineages, including the wild-type, a cystine importer-disrupted mutant, a complemented strain, and a cystine importer-overexpressed strain. Cellular growth reached early exponential growth at OD600 2.0 and late exponential growth at OD600 4.0. Exposing the cells to hydrogen peroxide (80–100 mM) resulted in the transposition of insertion sequences (ISs) in genes associated with the carotenoid biosynthesis pathway. Particularly, ISDge7 (an IS5 family member) and ISDge5 (an IS701 family member) from the cystine importer-disrupted mutant were transposed into phytoene desaturase (dgeo_0524) via replicative transposition. Further, the cystine importer-overexpressed strain Δdgeo_1985R showed transposition of both ISDge2 and ISDge5 elements. In contrast, IS transposition was not detected in the complementary strain. Interestingly, a cystine importer-overexpressing strain exhibited streptomycin resistance, indicating that point mutation occurred in the rpsL (dgeo_1873) gene encoding ribosomal protein S12. qRT-PCR analyses were then conducted to evaluate the expression of oxidative stress response genes, IS elements, and low-molecular-weight thiol compounds such as mycothiol and bacillithiol. Nevertheless, the mechanisms that trigger IS transposition in redox imbalance conditions remain unclear. Here, we report that the active transposition of different IS elements was affected by intracellular redox imbalances caused by cystine importer deficiencies or overexpression.

Active Transposition of Insertion Sequences in Prokaryotes: Insights from the Response of Deinococcus geothermalis to Oxidative Stress

“…Furthermore, we additionally demonstrated specialised IS transposition in the redoximbalance condition using a cystine importer-disrupted mutant and its complementary strain [26]. Interestingly, both ISDge5 of the IS701 family and ISDge7 of the IS5 family transposed to carotenoid biosynthesis genes, resulting in the non-pigmented phenotype (Figure 3).…”

“…Interestingly, dps gene-deficient mutants no longer expressed bshA, a gene required for bacillithiol biosynthesis [31]. However, WT and redox-imbalanced strains revealed similar expression levels of bshA [26]. Under oxidative stress, dps-deficient mutants revealed dramatically enhanced expression of mycothiol biosynthesis enzymes, such as MshBCD, specifically at the early exponential growth phase.…”

“…Most DDE-motif Tpases have a "copy-and-paste" mechanism [2,10,11]. In the case of D. geothermalis, the active transpositions of several IS elements of the IS1, IS5, IS6 and IS701 families perform this "copy-and-paste" or a replicative mode of transposition [24][25][26]. Briefly, the expressed Tpase bound to itself on the end of the IS element and cleavage covalent bond between adjacent nucleotides and the template DNA synthesised nascent strand in both strands.…”

“…Among different D. geothermalis lineages, the following specific types of IS elements actively transposed to carotenoid biosynthesis genes (phytoene cyclase and phytoene desaturase) and an rsmG gene (conferring streptomycin resistance) with a replicative mode due to hydrogen peroxide-induced oxidative stress conditions: ISDge6 of the IS5 family in a LysR family regulator-disrupted mutant, ISDge5 of the IS701 family in a dps gene (encoding a chromosome stabilizer protein, Dps: DNA-binding protein from starved cells)-disrupted mutant strain and a cystine importer-disrupted mutants and ISDge11 of the IS4 family in the wild-type strain (Figure 2) [24][25][26]. Nevertheless, the scheme III transposition events of IS elements with different TIR sequences and the scheme IV transposition events of IS elements without DR sequences have not yet been found under the oxidative stress condition in WT and target gene-disrupted mutants [31].…”

Adaptive Response of Thermophiles to Redox Stress and Their Role in the Process of dye Degradation From Textile Industry Wastewater

“…Glutathione (GSH) and thioredoxin (Trx) systems that scavenge harmful intracellular ROS are capable of controlling redox reactions. Redox reactions often involve molecules with thiol or sulfhydryl (-SH) functional groups, including low-molecular-weight (LMW) thiols, cystine-derived thiols, and redoxins ( Ye et al, 2021 ). Intra-or intermolecular disulfide reduction by Trx is one example of redox-based regulation.…”