We hypothesize that bladder E. coli plasmids increase resistance to lysis by bacteriophage (phage). The aim of the study is to conjugate bladder E. coli plasmids into a control strain and assess if the control strain is more resistant to phage infection.

To assess the effect of phage on the bladder microbiota, we must determine the host range of bladder phage and understand genetic determinants associated with that host range. We utilize E. coli phages P1, Greed, and Lust as a model system to identify genetic content differences between E. coli strains susceptible and resistant to infection by bladder coliphages. Using a standard phage lysis assay, we screened E. coli urine bladder isolates (UMB), standard lab strains (B, C, K-12), and uropathogenic E. coli (UPEC). All lab E. coli strains (K-12, B, C) and three UMB strains were susceptible to both Greed and Lust. We then analyzed the genomes of the screened E. coli strains to computationally identify plasmidic genome content and cluster based on sequence homology. We conjugated bladder E. coli plasmids from each cluster into the lysis-susceptible E. coli K-12 and tested for changes in its resistance to phage lysis.

We determined that plasmids are present in many of the strains resistant to phage lysis. Sequence comparison allowed us to separate plasmids into three distinct clusters. A plasmid from each cluster was conjugated into an E. coli K-12 recipient; K-12 transconjugant strains are more resistant to lytic phage infection.

Bacteria populations in the bladder microbiome can fluctuate drastically from day to day, which may have implications for bladder health. Phage can interact with bacteria in complex ways: they can eradicate bacterial populations via cell lysis, provide genetic traits to bacteria via transduction and chromosome integration, and block infection by other phages. Phage are abundant and diverse in the bladder, and their presence correlates with horizontal acquisition of genetic content by bladder bacteria. Bacteria benefit from modulating phage infection so that they will not be consumed, but instead gain beneficial traits. Plasmids in bacteria may be a vector for the acquisition of genes that can modulate phage infection.

Phage may be a major player in microbiome dynamics, and plasmids in bacteria may influence phage infection. Here, we demonstrate evidence that plasmids from bladder E. coli increase resistance to phage lysis in the previously susceptible lab strain E. coli K-12. Plasmids may be an easily transmissible vector in the urinary microbiome that could be used by bacteria to defend themselves against phage infection.