No abstract

Thermophiles are atractive as host cells for microbial processes to produce or degrade various compounds. In these applications, it is often desirable to improve the properties of thermophiles, such as their growth rate, cell density, and protein productivity, although this is rarely achieved because of the lack of general approaches. In this chapter, we describe the elimination of the pHTA426 plasmid from a moderate thermophile, Geobacillus kaustophilus HTA426, and its efects on the microbial properties. This process, called plasmid curing, was simply achieved using a DNA intercalator and conirmed by phenotypic and genotypic analyses. Of note, pHTA426 curing had beneicial efects on diverse properties, probably because of the reduced energy burden in terms of plasmid replication at high temperatures. The result suggests that plasmid curing is a simple and versatile approach for improving thermophiles. In particular, this approach may be efective for archaeal thermophiles because they grow at much higher temperatures and could have the greater energy burden on plasmid replication. Data mining has also shown that plasmids are distributed in archaeal thermophiles. This chapter provides a new tip for improving archaeal thermophiles, thereby increasing the opportunities for their use in various biotechnological applications.