Responses of a desert cyanobacterium to prolonged exposure to perchlorate: implications for the habitability of Mars and In-Situ Resource Utilization
Authors: Gallego Fernandez Beatriz , Mosca Claudia , Fagliarone Claudia , Billi Daniela 
Published: September 2022

&lt;p class=&quot;western&quot; align=&quot;justify&quot;&gt;&lt;span lang=&quot;en-US&quot;&gt;Martian regolithic soil is considered an inhospitable &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;environment&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; to life as we know it with low availability of nutrients and the presence &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;of powerful oxidants, namely perchlorate &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;salts&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;. Extreme microorganisms such as cyanobacteria of the genus &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;Chroococcidiopsis&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; dominate rock-dwelling communities in extreme deserts resembling the actual Martian environment. The strain &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;Chroococcidiopsis&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; 029, extremely tolerant to desiccation, ionizing, and UV radiation, can thrive in Mars-like conditions in a dried state. In the present work, we investigated the response of &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;Chroococcidiopsis&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; 029 when grown for a 3-week period using Martian regolith simulant containing 2.4 mM &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;perchlorate anions&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;. The growth either in the planktonic cells or biofilm life style was monitored following the in chlorophyll &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;a&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; content. The cellular and molecular responses to 2.4 mM &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;perchlorate anions&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt; was studied following cell viability according to: i) PCR-PMA assay, ii) changes in gene expression of three SOD-coding genes (&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;soda 2.1, soda.2, and sodC&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;), and iii) production of intracellular ROS as rev&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;e&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;aled by CLSM. Results suggested that perchlorate did not compromise cell viability and that a significant over-expression of three SOD isoforms occurred after the one-week exposure with a greater expression of the membrane-bound MnSOD (&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;sodA 2.1&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;) in comparison to the cytoplasmic isoforms MnSOD (&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;sodA 2.2&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;) and Cu/ZnSOD (&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;&lt;em&gt;sodC&lt;/em&gt;&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;). The accumulation of ROS within the cells was observed after 1-day exposure to perchlorate. Future investigations on the effect of Mars-like conditions in hydrated biofilms with 2.4 mM ClO4- and Martian regolith simulant will be carried out supported by the Europlanet scholarship 202&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;4&lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;. These results are relevant for the habitability of Mars and the development of In-situ Resource Utilization.&lt;/span&gt;&lt;/p&gt;