An Antarctic Extreme Halophile and Its Polyextremophilic Enzyme: Effects of Perchlorate Salts
Effects of perchlorate salts prevalent on the surface of Mars are of significant interest to astrobiology from the perspective of potential life on the Red Planet. Halorubrum lacusprofundi, a cold-adapted halophilic Antarctic archaeon, was able to grow anaerobically on 0.04 M concentration of perchl...
| Published in: | Astrobiology |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Mary Ann Liebert Inc.
2018
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| Subjects: | |
| Online Access: | http://hdl.handle.net/10713/8800 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045838301&doi=10.1089%2fast.2017.1766&partnerID=40&md5=8445a0e559c9f9e69b3c4552c4206696 https://doi.org/10.1089/ast.2017.1766 |
| Summary: | Effects of perchlorate salts prevalent on the surface of Mars are of significant interest to astrobiology from the perspective of potential life on the Red Planet. Halorubrum lacusprofundi, a cold-adapted halophilic Antarctic archaeon, was able to grow anaerobically on 0.04 M concentration of perchlorate. With increasing concentrations of perchlorate, growth was inhibited, with half-maximal growth rate in ca. 0.3 M NaClO4 and 0.1 M Mg(ClO4)2 under aerobic conditions. Magnesium ions were also inhibitory for growth, but at considerably higher concentrations, with half-maximal growth rate above 1 M. For a purified halophilic ?-galactosidase enzyme of H. lacusprofundi expressed in Halobacterium sp. NRC-1, 50% inhibition of catalytic activity was observed at 0.88 M NaClO4 and 0.13 M Mg(ClO4)2. Magnesium ions were a more potent inhibitor of the enzyme than of cell growth. Steady-state kinetic analysis showed that Mg(ClO4)2 acts as a mixed inhibitor (KI = 0.04 M), with magnesium alone being a competitive inhibitor (KI = 0.3 M) and perchlorate alone acting as a very weak noncompetitive inhibitor (KI = 2 M). Based on the estimated concentrations of perchlorate salts on the surface of Mars, our results show that neither sodium nor magnesium perchlorates would significantly inhibit growth and enzyme activity of halophiles. This is the first study of perchlorate effects on a purified enzyme. � Victoria J. Laye and Shiladitya DasSarma. 2018. We thank Priya DasSarma for assistance with culturing of halophiles. This work was supported by National Aeronautics and Space Administration grant NNX15AM07G. https://dx.doi.org/10.1089/ast.2017.1766 |
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