The Survival of Haloferax mediterranei under Stressful Conditions

Abstract

Haloarchaea can survive and thrive under exposure to a wide range of extreme environmental factors, which represents a potential interest to biotechnology. Growth responses to different stressful conditions were examined in the haloarchaeon Haloferax mediterranei R4. It has been demonstrated that this halophilic archaeon is able to grow between 10 and 32.5% (w/v) of sea water, at 32–52 °C, although it is expected to grow in temperatures lower than 32 °C, and between 5.75 and 8.75 of pH. Moreover, it can also grow under high metal concentrations (nickel, lithium, cobalt, arsenic), which are toxic to most living beings, making it a promising candidate for future biotechnological purposes and industrial applications. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis quantified the intracellular ion concentrations of these four metals in Hfx. mediterranei, concluding that this haloarchaeon can accumulate Li+, Co2+, As5+, and Ni2+ within the cell. This paper is the first report on Hfx. mediterranei in which multiple stress conditions have been studied to explore the mechanism of stress resistance. It constitutes the most detailed study in Haloarchaea, and, as a consequence, new biotechnological and industrial applications have emerged.

Analysis of Haloferax mediterranei Lrp Transcriptional Regulator

“…salinarum, cells could not grow above 16 mM H2O2. For this reason, the tested concentrations were not higher [30]. At low concentrations, between 2 and 8 mM H2O2, the promoter activity is not detected, while the activity of β-galactosidase slightly increases at higher concentrations (14 mM) of hydrogen peroxide (Figure 6C).…”

“…All values in figures are expressed as the mean of three replicates ± the standard deviation. * The addition of hydrogen peroxide and heavy metals were performed as [30]. All the media were inoculated at OD 600 0.02 with pre-adapted cells.…”

“…Hfx. mediterranei is metabolically very versatile, growing using a wide range of carbon and nitrogen sources and, even, in the presence of heavy metals [30,31]. The high number of Lrp/AsnC proteins, compared with other haloarchaeal species, may allow Hfx.…”

“…The four metals (Li +, Co 2+ , As 5+ , and Ni 2+ ) tested in this assay are tolerated by Hfx. mediterranei and incorporated into its cellular interior [30]. There is a previous assay about a bacterial heavy-metal resistance system controlled by an Lrp-type transcriptional regulator in Bacillus subtilis [56].…”

Novel Glutamate–Putrescine Ligase Activity in Haloferax mediterranei: A New Function for glnA-2 Gene

“…In recent years, Haloferax mediterranei has become one of the best-known halophilic microorganisms belonging to the Archaea domain and is considered to be a model organism for studying nitrogen metabolism [10][11][12][13][14][15][16][17][18][19][20], in addition to tolerance to environmental stress agents [21], thus making it a promising candidate for future biotechnological applications. In relation to nitrogen metabolism, Hfx.…”