Biodiversity of Aeromonad Myophages: Preliminary Polyphasic Survey of a Collection of A. hydrophila Phages Isolated in the Philippines

Through a polyphasic approach in classifying bacteriophages, this study determined phenotypic characteristics (stability pH, temperature and saline concentrations, and host range) and genotypic properties using the major capsid gene (g23). Eighteen (18) Aeromonas hydrophila phages (avJB2, avJB3, avJB4, avJB6, avTRAC18, avUSTBG, avSP1, avSP4, avSP5, avSL1, avSL2, av10AA, av10AB, av10BA, av2AA, av2AB, av2AC, and av2BA) previously isolated from different source samples (sewage, lake, pond, and river) were acquired from the Manila, the Philippines, and were initially propagated using the host bacterium, (A. hydrophila BIOTECH 10089). Physiological characterization of phages through stability testing, and host range showed the phages isolated from sewage and polluted river systems exhibited the most stability and polyvalency in infection. Moreover, through these characteristics, the diversity of the phages in the collection was established, resulting in 71% viable phages with varying characteristics. Phylogenetic analysis of g23 sequences, coupled with the phenotypic characteristics of the phages, suggested a highly unique set of phages isolated from four sample types (i.e. sewage, lake, river, and aquaculture pond) that infect A. hydrophila and high similarity in a structural gene sequence, evident in the isolated clustering of these entities when compared with reference phages. The results indicate a widespread distribution of related Aeromonad phages in the country, with phenotypic characteristics that cannot be limited to its environment. Finally, the unique clustering of all 16 Philippine Aeromonad phages –, based on capsid gene (g23) sequences, – suggests a novel group of myophages under the genus Biquartavirus.