Scuola Superiore Meridionale (SSM), Via Mezzocannone 4, 80138, Naples, Italy.
Department of Chemical Sciences, University of Naples Federico II, Via Cintia 26, 80126, Naples, Italy.
Phys Chem Chem Phys. 2024 Jan 3;26(2):760-769. doi: 10.1039/d3cp03911k.
Biomembranes are a key component of all living systems. Most research on membranes is restricted to ambient physiological conditions. However, the influence of extreme conditions, such as the deep subsurface on Earth or extraterrestrial environments, is less well understood. The deep subsurface of Mars is thought to harbour high concentrations of chaotropic salts in brines, yet we know little about how these conditions would influence the habitability of such environments. Here, we investigated the combined effects of high concentrations of Mars-relevant salts, including sodium and magnesium perchlorate and sulphate, and high hydrostatic pressure on the stability, structure, and function of a bacterial model membrane. To this end, several biophysical techniques have been employed, including calorimetry, fluorescence and CD spectroscopy, confocal microscopy, and small-angle X-ray scattering. We demonstrate that sulphate and perchlorate salts affect the properties of the membrane differently, depending on the counterion present (Na Mg). We found that the perchlorates, which are believed to be abundant salts in the Martian environment, induce a more hydrated and less ordered membrane, strongly favouring the physiologically relevant fluid-like phase of the membrane even under high-pressure stress. Moreover, we show that the activity of the phospholipase A2 is strongly modulated by both high pressure and salt. Compellingly, in the presence of the chaotropic perchlorate, the enzymatic reaction proceeded at a reasonable rate even in the presence of condensing Mg and at high pressure, suggesting that bacterial membranes could still persist when challenged to function in such a highly stressed Martian environment.
生物膜是所有生命系统的关键组成部分。大多数关于膜的研究都局限于环境生理条件。然而，对于极端条件的影响，如地球深部或外星环境的影响，了解得较少。火星的深部被认为在盐水中有高浓度的离液盐，然而我们对这些条件如何影响这些环境的宜居性知之甚少。在这里，我们研究了高浓度与火星相关的盐（包括高氯酸钠和高氯酸钠和硫酸盐）以及高静水压力对细菌模型膜的稳定性、结构和功能的综合影响。为此，我们采用了几种生物物理技术，包括量热法、荧光和 CD 光谱学、共聚焦显微镜和小角 X 射线散射。我们证明硫酸盐和高氯酸盐盐根据存在的反离子（Na、Mg）以不同的方式影响膜的性质。我们发现，高氯酸盐，据信是火星环境中丰富的盐，诱导更水合和无序的膜，强烈有利于膜的生理相关的流体相，即使在高压下也是如此。此外，我们表明磷脂酶 A2 的活性受到高压和盐的强烈调节。引人注目的是，在离液高氯酸盐的存在下，即使在凝结的 Mg 和高压下，酶反应也以合理的速率进行，这表明当细菌膜在如此高压力的火星环境中受到挑战时，它们仍然可以存在。
