AUTHOR=Yuan Changguo , Li Ping , Qing Chun , Kou Zhu , Wang Helin 

TITLE=Different Regulatory Strategies of Arsenite Oxidation by Two Isolated Thermus tengchongensis Strains From Hot Springs

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.817891

DOI=10.3389/fmicb.2022.817891

ISSN=1664-302X

ABSTRACT=<p>Arsenic is a ubiquitous constituent in geothermal fluids. Thermophiles represented by <italic>Thermus</italic> play vital roles in its transformation in geothermal fluids. In this study, two <italic>Thermus tengchongensis</italic> strains, named as 15Y and 15W, were isolated from arsenic-rich geothermal springs and found different arsenite oxidation behaviors with different oxidation strategies. Arsenite oxidation of both strains occurred at different growth stages, and two enzyme-catalyzed reaction kinetic models were observed. The arsenite oxidase of <italic>Thermus</italic> strain 15W performed better oxidation activity, exhibiting typical Michaelis–Menten kinetics. The kinetic parameter of arsenite oxidation in whole cell showed a <italic>V</italic><sub><italic>max</italic></sub> of 18.48 μM min<sup>–1</sup> and <italic>K</italic><sub><italic>M</italic></sub> of 343 μM. Both of them possessed the arsenite oxidase-coding genes <italic>aioB</italic> and <italic>aioA</italic>. However, the expression of gene <italic>aioBA</italic> was constitutive in strain 15W, whereas it was induced by arsenite in strain 15Y. Furthermore, strain 15Y harbored an intact <italic>aio</italic> operon including the regulatory gene of the ArsR family, whereas a genetic inversion of an around 128-kbp fragment produced the inactivation of this regulator in strain 15W, leading to the constitutive expression of <italic>aioBA</italic> genes. This study provides a valuable insight into the adaption of thermophiles to extreme environments.</p>