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.
Highlights
Data for each pH value were significant among the groups and the control (p ≤ 0.05), as shown in Figure 2b and Table 2. These results show that the growth was slower at extreme acidic or alkaline pH, Hfx. mediterranei R4 can grow over a wide pH range, and the study of its adaptation strategies may provide interesting insights into the physiology and survival mechanisms of Haloarchaea
Hfx. mediterranei can adapt to harsh conditions such as low/high temperatures, low/high salt concentrations, changes in pH, oxidative stress, and the addition of metals (Ni2+, Li+, Co2+, As5+ )
Adapting to extreme conditions is an important advantage of living beings, considering, on one hand, that extreme adverse conditions are increasingly frequent due to climate change and, on the other hand, the possibility of developing new and promising biotechnological processes
Summary
Environmental stress has impacted all three domains of life, causing a devasting impact on growth. Microbial communities have evolved and survived through exposure to stressful conditions such as low/high solar radiation, extreme temperatures, oxidative stress, pH variations, salinity changes, heavy metals, or desiccation hydration cycles [1,2]. To survive in these conditions, organisms must adapt by shifting away from their optimum growth conditions. Cells change from a growth state to a survival-state to return to homeostasis and avoid damage; the growth rate observed by optical density decreases
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