This was a really challenging study where we attempted to characterise the biology of hundreds of temperate bacteriophages from the human gut - in the lab! This required anaerobic chambers to grow the gut bacteria, entirely new methods to induce and study the bacteriophages.

Placing this conclusion more broadly - our field is on the precipice of increased application of phages to human patients in an attempt to combat superbug infections.

Our work suggests we should remove our blinders to explore potential symbiotic phage-mammalian interactions.

Once these phages are internalised, a proportion of them are likely degraded and metabolised by the cell.

From a macromolecular stance, phages are condensed packets of nucleotides wrapped in a protein shell.

Thus, they may provide an exogenous source of key nutrients.

We then confirmed these phenomena using a cell proliferation assay.

In vitro mammalian cells treated with phage broadly showed an increase in their proliferation over 72 hours, which correlated with a prolonged G0/G1 cell cycle growth phase.

Next, we used extensive antibody microarrays from
Kinexus, consisting of >1000 antibodies targeting broad cellular pathways

Phage treatment to cells induced broad and extensive protein-phosphorylation events leading to increases in cellular metabolism, growth and proliferation

We first show that the application of purified T4 phage across three mammalian cell lines led to rapid uptake and internalisation, but importantly, did not trigger a pro-inflammatory response.

This suggests that cells carefully traffick and process phage particles.