Ff phages

Abstract: The circular, single-stranded DNA genome of the Pf3 bacteriophage was sequenced in its entirety by each of two methods, the M13-dideoxy chain termination method and the chemical degradation method. It consists of 5,833 nucleotides. With respect to both the DNA and the protein sequences, there is virtually no homology between Pf3 and the phages Ff (M13, f1, and fd) and IKe. However, similarities between these phages were noted with respect to their overall genome organizations. The gene for the single-stranded DNA-binding protein is followed by the gene for the major coat protein and then by a transcription termination signal. Open reading frames for seven other proteins were predicted, and their sizes and order show a fair correspondence to the sizes and order of the genes of the Ff phages and IKe. In addition, several regions have the potential to form stem and loop structures similar to those in the intergenic region of the Ff phage genome, but in Pf3 some are within open reading frames. Evolutionary relationships between Pf3 and the Ff phages and IKe are thus apparent through the correspondence of overall gene order rather than through primary sequence homologies.

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. Keywords: filamentous bacteriophage; ssDNA viruses; phage display; nanotechnology; Vibrio cholerae; E. coli; Xanthomonas; Pseudomonas; bacterial surfaces; bacterial secretion

Abstract: Bacteriophages (phages) are ubiquitous viruses that control the growth and diversity of bacteria. Although they have no tropism to mammalian cells, accumulated evidence suggests that phages are not neutral to the mammalian macro-host and can promote immunomodulatory and anti-tumorigenic activities. Here we demonstrate that Ff phages that do not display any proteins or peptides could inhibit the growth of subcutaneous glioblastoma tumors in mice and that this activity is mediated in part by lipopolysaccharide molecules attached to their virion. Using the intranasal route, a non-invasive approach to deliver therapeutics directly to the CNS, we further show that phages rapidly accumulate in the brains of mice and could attenuate progression of orthotopic glioblastoma. Taken together, this study provides new insight into phages non-bacterial activities and demonstrates the feasibility of delivering Ff phages intranasally to treat brain malignancies.