Filamentous Bacteriophages: Biology and Applications

Abstract

Filamentous bacteriophages contain a circular single‐stranded deoxyribonucleic acid (ssDNA) genome packaged into long filaments. These phages do not reproduce by lysing bacteria; instead, they are secreted into the environment without killing the host. Well‐studied Escherichia coli K12‐infecting Ff phages (f1, fd or M13) always replicate episomally; however a growing number of ‘lysogenic’ or chromosomally integrated filamentous phages of Gram‐negative bacteria are being discovered. The ‘lysogens’ can be induced; however phage reproduction does not require genome excision from bacterial chromosome and does not lyse the host cells. Some filamentous phages enhance the virulence of their host organisms, the most striking example being the CTXφ of Vibrio cholerae , which encodes cholera toxin. E. coli Ff phages are the workhorse of phage display technology, whose most notable ‘products’ are therapeutic recombinant antibodies. Ff are also being used in nanotechnology as templates for assembly of nanostructures, which has already led to their incorporation into a working nanobattery. Key Concepts: Filamentous bacteriophages are long filaments (6–7 nm×>500 nm) that contain a single‐stranded circular DNA genome. Filamentous bacteriophages replicate via a rolling circle mechanism, one strand at a time. Filamentous bacteriophages do not lyse the cells; they are released by secretion, using a dedicated filamentous phage assembly secretion system. Filamentous phage secretion‐assembly requires the proton‐motive force and ATP. Some filamentous phages replicate exclusively as episomes, while others also integrate their genomes into the host chromosome, forming a lysogen. Induction of the lysogen does not result in cell lysis. Ff filamentous phages of E. coli (f1, M13 and fd) have been used interchangeably as vectors and helper phages in DNA sequencing, as a protein display platform in phage display technology and as a template for assembly of nanostructures in nanotechnology.

Filamentous phages of Ralstonia solanacearum: double-edged swords for pathogenic bacteria

“…Infection with this kind of phage does not cause host cell lysis, but establishes a persistent association between the host and phage, producing and releasing phage particles from the growing and dividing host cells. In general, the genome of inoviruses, represented by Escherichia coli F-pillus specific phage Ff (f1, fd or M13), is organized in a modular structure, in which functionally related genes are grouped together (Horiuchi et al, 2009; Rakonjac et al, 2011). Three functional modules are always present: the replication module, the structural module, and the assembly and secretion module.…”

Application of filamentous phages in environment: A tectonic shift in the science and practice of ecorestoration

“…In fact, plants exert niche-specific selection pressure on the organisms associated with them; for example, strains of E. coli associated with plants are a distinct phenotype and make an independent phylogroup different from that purified from mammalian hosts (Méric, Kemsley, Falush, Saggers, & Lucchini, 2013 Filamentous phage-infected P. aeruginosa shows high potential to colonize different habitats because of its ability to form biofilms, which have a liquid crystalline organizational structure (Rice et al, 2009;Secor et al, 2015). The biofilm is not an inert structure but a cooperative and interactive network that develops into an ecologically cohesive microbial community, which can rapidly colonize the target site (Hengzhuang, Wu, Ciofu, Song, & Høiby, 2011, 2012Høiby et al, 2011;Høiby, Bjarnsholt, Givskov, Molin, & Ciofu, 2010). In fact, Pf1-infected P. aeruginosa PAO1 strains outcompete the noninfected strains in forming a biofilm and also form a cohesive group for exchanging genes-exchanges from which the noninfected strains are excluded (Whiteley et al, 2001).…”

Bacteriophages and phage-inspired nanocarriers for targeted delivery of therapeutic cargos

“…The genome of episomal phages replicates in the bacterial cytoplasm, whereas the genome of chromosomally integrated lysogenic phages is transferred into the host chromosome. The assembly process of the newly produced phages is performed by coating the phage DNA with the pVIII and pIII proteins[40]. …”