Interactions between Prokaryotic Viruses and Their Hosts

Dear Colleagues,

Bacteria and archaea are major players in global biogeochemical cycles. These prokaryotes predominate the cellular form of life on Earth, and they coexist with their viruses, i.e., bacteriophages or phages and archaeal viruses, in all environments. Recent studies show that soils and sediments represent the richest sources of prokaryotic viruses where they outnumber their hosts by 2–3 orders of magnitude. Metagenomic analyses further reveal that many novel bacteriophages are present in the intestines of animals and human beings where the ratio of virus/host cells is estimated to be 1:1, a number that is doomed to increase due to the growth of ongoing research in the field. To date, 60–99% of viral genes in viromes generated from diverse biomes have unknown functions, and more than 99% of viral diversity remains to be explored. These viruses and their prokaryotic hosts interact with each other antagonistically and beneficially to influence nutrient cycling and ecological functions, but little has been found regarding their host–virus interactions. Furthermore, bacteria and archaea encode an arsenal of antiviral systems, many of which are novel. For example, focused research on model CRISPR-Cas systems have revealed that prokaryotic hosts deploy adaptive immunity to defend themselves from a virus invasion, whereas viruses encode anti-CRISPR systems to subvert CRISPR immunity. Since there is a great diversity both in CRISPR-Cas systems and anti-CRISPR systems, much more remains to be learned with regard to the arms race between prokaryotic hosts and their viruses. In addition, several pioneer research studies have revealed additional novel bacterial and archaeal antiviral systems, representing a new direction for prokaryotic virus research.

This Special Issue is dedicated to publishing research articles, reviews, perspectives and opinion articles with a focus on studying interactions between bacterial and archaeal hosts and their viruses. The article collection covers, but is not limited to, the following research areas:

1. Identification and functional characterization of novel prokaryotic viruses including bacteriophages and archaeal viruses;
2. Mechanisms of virus infection, such as identification of novel receptors for infection or revealing mechanisms of infection by novel viruses;
3. Identification of global regulators controlling/modulating the expression of viral and host genes;
4. The novel mechanism of antiviral defense by innate and adaptive immune systems as well as signaling systems and abortive infection, such as R-M systems, CRISPR-Cas systems, CBASS, etc.;
5. The arms race between host-encoded antiviral systems and virus-encoded proteins that subvert the host immunity.

Prof. Dr. Qunxin She
Prof. Dr. Yuqing Liu
Guest Editors

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• bacteriophages
• archaeal viruses
• mechanisms of virus infection
• R-M systems
• CRISPR-Cas systems
• cOA signaling
• abortive infection
• anti-CRISPR
• arms race
• host–virus interactions