Abstract: Filamentous phages are widely distributed in Gram-negative bacteria.In contrast to lytic phages, after the filamentous phage infects the host, it integrates its genome into the host chromosome through specific recognition sites, and uses the host DNA replication mechanism to complete its own DNA replication.Finally, the mature filamentous phage is secreted and released through the host cell membrane, while the host bacteria can still proliferate, but the growth rate slows down.Since 1996 Vibrio cholerae filamentous phage CTXφ were found to contain the genes encoding cholera toxin, filamentous phages have attracted considerable attention for their interaction with host bacteria.In recent years, numerous studies have shown that filamentous bacteriophages are not only important in horizontal gene transfer but also endow host bacteria with many characteristics related to pathogenicity and viability.This review presents an overview of the role of filamentous phages in host adaptation, including enhancing bacterial biofilm formation, encoding bacterial toxins, modulating production and release of toxins, helping bacteria to adapt the extreme marine environment, helping bacteria resist repeated infection of bacteriophages, so as to increase understanding of filamentous bacteriophage-host interaction, and provide the guidance and basis for bacteriophage therapy to prevent and control bacterial diseases.

Key words: filamentous phage; environmental adaptation; bacterial virulence; biofilms; hyperinfection rejection