Genome-wide transcriptional response to silver stress in extremely halophilic archaeon Haloferax alexandrinus DSM 27206 T

Abstract

Background The extremely halophilic archaeon Haloferax (Hfx.) alexandrinus DSM 27206 T was previously documented for the ability to biosynthesize silver nanoparticles while mechanisms underlying its silver tolerance were overlooked. In the current study, we aimed to assess the transcriptional response of this haloarchaeon to varying concentrations of silver, seeking a comprehensive understanding of the molecular determinants underpinning its heavy metal tolerance. Results The growth curves confirmed the capacity of Hfx. alexandrinus to surmount silver stress, while the SEM–EDS analysis illustrated the presence of silver nanoparticles in cultures exposed to 0.5 mM silver nitrate. The RNA-Seq based transcriptomic analysis of Hfx. alexandrinus cells exposed to 0.1, 0.25, and 0.5 mM silver nitrate revealed the differential expression of multiple sets of genes potentially employed in heavy-metal stress response, genes mostly related to metal transporters, basic metabolism, oxidative stress response and cellular motility. The RT-qPCR analysis of selected transcripts was conducted to verify and validate the generated RNA-Seq data. Conclusions Our results indicated that copA, encoding the copper ATPase, is essential for the survival of Hfx. alexandrinus cells in silver-containing saline media. The silver-exposed cultures underwent several metabolic adjustments that enabled the activation of enzymes involved in the oxidative stress response and impairment of the cellular movement capacity. To our knowledge, this study represents the first comprehensive analysis of gene expression in halophillic archaea facing increased levels of heavy metals.

Halophilic archaea as tools for bioremediation technologies

“…It has also been described the capability of several haloarchaea to produce nanoparticles in the presence of metals. For example, Haloferax alexandrinus RK_AK2, Haloferax lucentense RK_MY6, Halococcus salifodinae BK3, and Halococcus salifodinae BK18 can make silver nanoparticles (Srivastava et al 2013 , 2014 , 2015 ; Moopantakath et al 2022 ; Buda et al 2023 ). The production of gold particles as well as particles from metalloids like selenium has also been described from the Haloferax genus [60, 61].…”