Viruses are the most abundant biological entities and represent the largest reservoir of uncharacterized genetic diversity on Earth. Interactions with their microbial hosts are one of the most common biological associations in ecology. While lytic phages acts as the primary agents of microbial mortality and, thus as drivers of nutrient and energy cycling in all studied econiches, lysogenic phages confer morphological or metabolic properties to the host that increase host, and presumably also, prophage fitness. Consistent with their overall importance as modifiers of microbial ecosystems, phages have been observed or isolated in a wide variety of environments, including acidic hot springs and acid mine drainages. The incidence of lysogeny in natural populations of acidophilic microorganisms has not been analysed to date.
Using more than 45 completed and 50 draft genomes from extreme acidophiles and a number of publically available prophage prediction tools, the incidence of lysogeny in acidophilic econiches was investigated. Correlation to genetic traits of the hosts (e.g. genome size, %G+C and codon usage), and the presence and properties of CRISPR loci in cognate genomes, was assessed through genome signature analysis, comparative genomics and CRISPR prediction tools. Greater numbers and greater diversity of candidate prophages were detected in archaeal acidophiles, where also longer and more diversified CRISPR loci were found. Results obtained this far suggest that temperate phages are more common in archaeal than in bacterial acidophiles, regardless of genome representativity. Statistics with respect to host genetic traits are presented and discussed.

Acknowledgements: Fondecyt 1140048, Basal PFB-16, Conicyt Scholarship (PC).