Engineering the Pseudomonas aeruginosa virus-isolation host viPAO1 reveals how host genetic barriers shape recoverable phage diversity

Cultured phage collections provide essential access to viral biology, but they capture only a small and biased fraction of natural phage diversity. Key barriers to diverse phage isolation are likely to include the prophages and defence systems present in the genomes of isolation hosts. Here, we show that removal of these host genetic barriers expands recoverable phage diversity in Pseudomonas aeruginosa. We constructed a series of progressively more permissive hosts derived from MPAO1 by sequentially deleting intracellular defence systems and resident prophages, culminating in viPAO1 (virus-isolation PAO1). Sequential removal of these barriers increased phage susceptibility, with Gabija and type I restriction-modification acting as major barriers to phage infection. In comparative isolation experiments, removal of intracellular barriers produced the largest increase in phage recovery, while additional receptor modification altered the composition of recovered phage subsets. viPAO1 also substantially increased recovery of phage contigs from environmental samples. Scaling this approach across 1090 clinical isolates enabled recovery of a curated collection of 69 individually purified temperate P. aeruginosa phages spanning 24 predicted genera, including 15 putative novel genera. Together, these findings demonstrate that removal of host genetic barriers to infection enhances recoverable phage diversity and establish permissive host engineering as a practical strategy for uncovering under-sampled regions of cultured phage diversity.