Production of selenium nanoparticles occurs through an interconnected pathway of sulphur metabolism and oxidative stress response in Pseudomonas putida KT2440

Abstract

The soil bacterium Pseudomonas putida KT2440 has been shown to produce selenium nanoparticles aerobically from selenite; however, the molecular actors involved in this process are unknown. Here, through a combination of genetic and analytical techniques, we report the first insights into selenite metabolism in this bacterium. Our results suggest that the reduction of selenite occurs through an interconnected metabolic network involving central metabolic reactions, sulphur metabolism, and the response to oxidative stress. Genes such as sucA, D2HGDH and PP_3148 revealed that the 2-ketoglutarate and glutamate metabolism is important to convert selenite into selenium. On the other hand, mutations affecting the activity of the sulphite reductase decreased the bacteria's ability to transform selenite. Other genes related to sulphur metabolism (ssuEF, sfnCE, sqrR, sqr and pdo2) and stress response (gqr, lsfA, ahpCF and sadI) were also identified as involved in selenite transformation. Interestingly, suppression of genes sqrR, sqr and pdo2 resulted in the production of selenium nanoparticles at a higher rate than the wild-type strain, which is of biotechnological interest. The data provided in this study brings us closer to understanding the metabolism of selenium in bacteria and offers new targets for the development of biotechnological tools for the production of selenium nanoparticles.

Superoxide Dismutase Catalyzed Size-Adjustable Selenium Nanoparticles in Saccharomyces boulardii

“…It was shown that yll058w was identified as an upregulated gene in both the selenium and sulfur metabolism pathways. Due to the chemical similarity between selenium and sulfur, under sodium selenite stress, sodium selenite is reduced through an interconnected metabolic network that includes selenium metabolism, sulfur metabolism, and the oxidative stress response . Therefore, enzymes in the selenium and sulfur metabolism pathways, such as TRR and YLL058W, are involved in the reduction pathway of sodium selenite, with key genes (such as trr1 , trr2 , and yll058w ) showing upregulated expression to maintain cellular redox balance and enhance redox activity.…”

Arsenite Mediates Selenite Resistance and Reduction in Enterobacter sp. Z1, Thereby Enhancing Bacterial Survival in Selenium Environments

“…Recently, an increasing number of studies have reported that Se­(IV) reduction functions as a detoxification mechanism in microorganisms. The reported Se­(IV) reduction pathways included a Painter-type reaction involving thiol groups, thioredoxin reductase system, siderophore-mediated reduction, sulfide-mediated reduction, and dissimilatory reduction. ,, Aerobic microorganisms can utilize electron donors such as thiol, sugars, hydrogen, NADP, and NADPH to reduce Se. − The gene grx A encodes a glutathione-dependent reductase that can aerobically reduce Se­(IV) into SeNPs in the P. stutzeri strain TS44 .…”

Opportunities and obstacles in microbial synthesis of metal nanoparticles

“…In addition, mutations affecting the activity of the sulphite reductase decreased the bacteria's ability to transform selenite into Se(0). Interestingly, suppression of genes sqrR , sqr and pdo2 resulted in the production of selenium nanoparticles at a higher rate than the wild‐type strain, which is an observation of great biotechnological interest (Avendaño et al, 2023 ).…”