Analysis of Haloferax mediterranei Lrp Transcriptional Regulator

Abstract

Haloferax mediterranei is an extremely halophilic archaeon, able to live in hypersaline environments with versatile nutritional requirements, whose study represents an excellent basis in the field of biotechnology. The transcriptional machinery in Archaea combines the eukaryotic basal apparatus and the bacterial regulation mechanisms. However, little is known about molecular mechanisms of gene expression regulation compared with Bacteria, particularly in Haloarchaea. The genome of Hfx. mediterranei contains a gene, lrp (HFX_RS01210), which encodes a transcriptional factor belonging to Lrp/AsnC family. It is located downstream of the glutamine synthetase gene (HFX_RS01205), an enzyme involved in ammonium assimilation and amino acid metabolism. To study this transcriptional factor more deeply, the lrp gene has been homologously overexpressed and purified under native conditions by two chromatographic steps, namely nickel affinity and gel filtration chromatography, showing that Lrp behaves asa tetrameric protein of approximately 67 kDa. Its promoter region has been characterized under different growth conditions using bgaH as a reporter gene. The amount of Lrp protein was also analyzed by Western blotting in different nitrogen sources and under various stress conditions. To sum up, regarding its involvement in the nitrogen cycle, it has been shown that its expression profile does not change in response to the nitrogen sources tested. Differences in its expression pattern have been observed under different stress conditions, such as in the presence of hydrogen peroxide or heavy metals. According to these results, the Lrp seems to be involved in a general response against stress factors, acting as a first-line transcriptional regulator.

Genomic analysis of heavy metal-resistant Halobacterium salinarum isolated from Sfax solar saltern sediments

“…Another mechanism used by halophilic archaea to deal with environmental variations, different stress conditions, and nutritional changes is the transcriptional gene regulation (Matarredona et al 2020 , 2021b ). The strains AS1 and AS2 show the highest number of genes coding for transcriptional regulators (30 and 29 genes respectively), whereas the other strains range between 19 and 20.…”

Diversity and functional traits of indigenous soil microbial flora associated with salinity and heavy metal concentrations in agricultural fields within the Indus Basin region, Pakistan

“…Curvularia have been noted to act as pathogens in some plant species, but promote plant growth in others via PGP activities such as P solubilization (Priyadharsini and Muthukumar, 2017). Finally, the absence of an effect of salinity or HM on α-diversity within the archaeal community was not surprising given the strong capacity of microbes within this to tolerate extreme environments, including high salinity (Matarredona et al, 2020). Nevertheless, the fact that there were potential differences in β-diversity indicate that some phylotypes, such as some of the Methanoncaldococcus, could be more sensitive to these stress factors.…”

Bioactive molecules from haloarchaea: Scope and prospects for industrial and therapeutic applications

“…In the low-salt-in method, some organisms produce compatible and low molecular-weight solutes to adapt to osmotic stress (Grant et al, 2004). The compatible solutes such as amino acids, ectoines, thetines, polyols, betaines, derivatives of sugar, and glutamine amide are accumulated in low concentration in the cytoplasm to tolerate osmotic stress (Matarredona et al, 2020). For instance, solutes like 2-sulphotrehalose, and glycine produced by Natronobacterium and Natronococcus, respectively, help in the low-salt process (Grant et al, 2004;Matarredona et al, 2020).…”