Newly Isolated Bacteriophages from the , , and Families Have Variable Effects on Putative Novel spp.

Soft rot pathogenic bacteria from the genus cause severe economic losses in orchid nurseries worldwide, and there is no effective control currently available. In the last decade, the genus has undergone multiple changes as multiple new taxa have been described, and just recently a new putative species was reported. This study reports the isolation of three bacteriophages active against putative novel spp. isolates from commercially produced infected orchids that show variable host-range profiles. Bacteriophages were isolated through enrichment from -infected orchid tissue. Convective interaction media monolith chromatography was used to isolate bacteriophages from wastewaters, demonstrating its suitability for the isolation of infective bacteriophages from natural sources. Based on bacteriophage morphology, all isolated bacteriophages were classified as being in the order , belonging to three different families, , , and . The presence of three different groups of bacteriophages was confirmed by analyzing the bacteriophage specificity of bacterial hosts, restriction fragment length polymorphism and plaque morphology. Bacteriophage BF25/12, the first reported bacteriophage effective against spp., was selected for further characterization. Its genome sequence determined by next-generation sequencing showed limited similarity to other characterized bacteriophages. Interactions among the bacteriophages and spp. were examined using transmission electron microscopy, which revealed degradation of electron-dense granules in response to bacteriophage infection in some strains. The temperature stability of the chosen bacteriophage monitored over 1 year showed a substantial decrease in the survival of bacteriophages stored at -20°C over longer periods. It showed susceptibility to low pH and UV radiation but was stable in neutral and alkaline pH. Furthermore, the stability of the tested bacteriophage was also connected to the incubation medium and bacteriophage concentration at certain pH values. Finally, the emergence of bacteriophage-resistant bacterial colonies is highly connected to the concentration of bacteriophages in the bacterial environment. This is the first report on bacteriophages against from the family to expand on potential bacteriophages to include in bacteriophage cocktails as biocontrol agents. Some of these bacteriophage isolates also showed activity against , an aggressive strain that causes the soft rot of potatoes, which indicates their broad potential as biocontrol agents.