Phage satellites and their emerging applications in biotechnology

ABSTRACT The arms race between (bacterio)phages and their hosts is a recognised hot spot for genome evolution. Indeed, phages and their components have historically paved the way for many molecular biology techniques and biotech applications. Further exploration into their complex lifestyles has revealed that phages are often parasitised by distinct types of hyperparasitic mobile genetic elements. These so-called phage satellites exploit phages to ensure their own propagation and horizontal transfer into new bacterial hosts, and their prevalence and peculiar lifestyle has caught the attention of many researchers. Here, we review the parasite–host dynamics of the known phage satellites, their genomic organisation and their hijacking mechanisms. Finally, we discuss how these elements can be repurposed for diverse biotech applications, kindling a new catalogue of exciting tools for microbiology and synthetic biology. Phage satellites are genetic elements with a modus vivendi linked to specific helper phages, which they hijack and exploit to propagate into new bacterial hosts. Their unique lifestyle and ability to exploit phages make them an attractive option for developing new biotechnologies, including gene delivery strategies and creating alternatives to antibiotics and phage therapy.