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Abstract

Activity of enzymes of polyamine synthesis and contents of their products increased in E. coli cells in response to oxidative stress caused by addition of hydrogen peroxide to an exponentially growing culture. Putrescine and spermidine added to the culture medium in physiological concentrations significantly increased expression of genes oxyR and katG responsible for defense against oxidative stress, whereas cadaverine had no effect. The role of polyamines as modulators of the gene expression was confirmed by experiments with an inhibitor of polyamine synthesis, 1,3-diaminopropane, which decreased the level of cell polyamines and thus abolished the ability of the cell to induce oxyR expression under oxidative stress. A genetic method gave similar results: under oxidative stress mutants with disorders in polyamine synthesis displayed a significantly decreased level of induction of the oxyR and katG genes, and this level was recovered on addition of putrescine. In the presence of inhibitors of DNA-gyrase, nalidixic acid and novobiocin, the oxyR expression depended on the extent of DNA supercoiling. Putrescine decreased the inhibitory effects of nalidixic acid and novobiocin, and this confirmed its properties of a stimulator of DNA supercoiling. Resistance to rifampicin was studied to exemplify the mutation rate under oxidative stress. Putrescine decreased twofold the level of mutations and increased the number of viable cells in the culture exposed to oxidative stress.

Putrescine Reduces Antibiotic-Induced Oxidative Stress as a Mechanism of Modulation of Antibiotic Resistance in Burkholderia cenocepacia

“…OxyR is very sensitive to ROS concentrations; it is activated at very low hydrogen peroxide concentrations, leading to upregulation to its regulon (34). Moreover, expression of oxyR is upregulated in response to hydrogen peroxide using LacZ promoter fusions (35); similarly, another LysR-type transcription regulator involved in the response to oxidative stress is overexpressed in response to ROS (36). Therefore, we constructed derivatives of wild-type and mutant strains carrying an oxyR::lux promoter fusion to measure oxyR gene expression at chromosomal levels.…”

Co-inhibition of Plasmodium falciparum S-Adenosylmethionine Decarboxylase/Ornithine Decarboxylase Reveals Perturbation-specific Compensatory Mechanisms by Transcriptome, Proteome, and Metabolome Analyses

“…Data of the respective biological replicates (A and B) are shown separately (T t1 had only one biological replicate because of technical difficulty). for DNA topoisomerase II (PF14_0316) (53), three oxidative stress defense transcripts (54), and transcripts involved with zinc transport and energy metabolism (55), which were all decreased.…”

Remaining Mysteries of Molecular Biology: The Role of Polyamines in the Cell

“…This includes scavenging of ROS [183][184][185][186][187], binding to membrane transport proteins [188][189][190], and regulating expression of proteins related to the stress response [191][192][193][194][195][196]. PAs can function as ROS scavengers as they are polycationic under physiological pH [183][184][185].…”

“…For example, in E. coli Put and Spd positively regulate the transcription of stress related transcription factors OxyR (peroxide detoxification), SoxRS (superoxide radical response) and RpoS (general stress) (reviewed in [197]). This leads to expression of genes such as ahpC (alkyl hydroperoxide reductase), katG (Catalase/hydroperoxidase I) and katE (hydroperoxidase II) [192,193]. In yeast, overexpression of the PA exporter, Tpo1, leads to sensitivity to H 2 O 2 , and prevents the induction of canonical stress proteins including Sod1, Hsp70, Hsp90 and Hsp104.…”