Evolutionary insights into provirus-encoded CRISPR-Cas systems in halophilic archaea.

ABSTRACT: Prokaryotic microorganisms coexist with mobile genetic elements (MGEs), which can be both genetic threats and evolutionary catalysts. In Haloferax lucentense, a halophilic archaeon, we have recently identified an unusual genomic arrangement: a complete type I-B CRISPR-Cas system encoded on a megaplasmid and an incomplete type I-B system within an integrated provirus in the main chromosome. The provirus-encoded system lacks the adaptation genes (cas1, cas2, and cas4), suggesting its potential reliance on the megaplasmid-encoded CRISPR-Cas module for the acquisition of new spacers. This arrangement suggests a potential instance of "adaptive outsourcing," where a provirus might leverage a co-resident MGE for a key function. Through comparative genomics, we show that simil

SUBMITTER: Naki D 

PROVIDER: S-EPMC12596717 | biostudies-literature | 2025

REPOSITORIES: biostudies-literature