AUTHOR=Ahmad Abdelmonim Ali , Askora Ahmed , Kawasaki Takeru , Fujie Makoto , Yamada Takashi 

TITLE=The filamentous phage XacF1 causes loss of virulence in Xanthomonas axonopodis pv. citri, the causative agent of citrus canker disease

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00321

DOI=10.3389/fmicb.2014.00321

ISSN=1664-302X

ABSTRACT=<p>In this study, filamentous phage XacF1, which can infect <italic>Xanthomonas axonopodis</italic> pv. <italic>citri</italic> (<italic>Xac</italic>) strains, was isolated and characterized. Electron microscopy showed that XacF1 is a member of the family <italic>Inoviridae</italic> and is about 600 nm long. The genome of XacF1 is 7325 nucleotides in size, containing 13 predicted open reading frames (ORFs), some of which showed significant homology to Ff-like phage proteins such as ORF1 (pII), ORF2 (pV), ORF6 (pIII), and ORF8 (pVI). XacF1 showed a relatively wide host range, infecting seven out of 11 strains tested in this study. Frequently, XacF1 was found to be integrated into the genome of <italic>Xac</italic> strains. This integration occurred at the host <italic>dif</italic> site (<italic>att</italic>B) and was mediated by the host XerC/D recombination system. The <italic>att</italic>P sequence was identical to that of <italic>Xanthomonas</italic> phage Cf1c. Interestingly, infection by XacF1 phage caused several physiological changes to the bacterial host cells, including lower levels of extracellular polysaccharide production, reduced motility, slower growth rate, and a dramatic reduction in virulence. In particular, the reduction in virulence suggested possible utilization of XacF1 as a biological control agent against citrus canker disease.</p>