CRISPR/Cas genome editing systems in thermophiles: Current status, associated challenges, and future perspectives

Thermophiles, offering an attractive and unique platform for a broad range of applications in biofuels and environment protections, have received a significant attention and growing interest from academy and industry. However, the exploration and exploitation of thermophilic organisms have been hampered by the lack of a powerful genome manipulation tool to improve production efficiency. At current, the clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR associated (Cas) system has been successfully exploited as a competent, simplistic, and powerful tool for genome engineering both in eukaryotes and prokaryotes. Indeed, with the significant efforts made in recent years, some thermostable Cas9 proteins have been well identified and characterized and further, some thermostable Cas9-based editing tools have been successfully established in some representative obligate thermophiles. In this regard, we reviewed the current status and its progress in CRISPR/Cas-based genome editing system towards a variety of thermophilic organisms. Despite the potentials of these progresses, multiple factors/barriers still have to be overcome and optimized for improving its editing efficiency in thermophiles. Some insights into the roles of thermostable CRISPR/Cas technologies for the metabolic engineering of thermophiles as a thermophilic microbial cell factory were also fully analyzed and discussed.