Phage-antibiotic synergy: cell filamentation is a key driver of successful phage predation

Phages are promising tools to fight antibiotic-resistant bacteria, and as for now, phage therapy is essentially performed in combination with antibiotics. Interestingly, combined treatments including phages and a wide range of antibiotics lead to an increased bacterial killing, a phenomenon called phage-antibiotic synergy (PAS), suggesting that antibiotic-induced changes in bacterial physiology alter the dynamics of phage propagation. Using single-phage and single-cell techniques, each step of the lytic cycle of phage HK620 was studied in E. coli cultures treated with either ciprofloxacin or cephalexin, two filamentation-inducing antibiotics. In the presence of sublethal doses of antibiotics, multiple stress tolerance and DNA repair pathways are triggered following activation of the SOS response. One of the most notable effects is the inhibition of bacterial division. As a result, a significant fraction of cells forms filaments that stop dividing but have higher rates of mutagenesis. A..., Phage-Antibiotic Synergy measurements. PAS measurements in liquid cultures were carried out by OD600measurements in a 96-well microplate. Briefly, a log-phase E. coli TD2158 PL4 culture was diluted to a final OD600 = 0.025. Subinhibitory antibiotic concentrations were added at this time. Replicates of 200 μL of each condition were dispensed in each well. After two hours of incubation at 37ºC under 180 rpm agitation, the same number of phages (phage titer PF/mL) was added to each replicate and lysis was observed by the reduction in OD600. Conversely, PAS measurements in semi-solid cultures were performed using the double agar overlay assay. For this, 10 mL of a log-phase culture of E. coli TD2158 PL4 at OD600 = 1 were infected with a final titer of 103 PFU/mL of phage HK620 and incubated at 37°C under 180 rpm agitation. Twenty-five minutes post-infection, 100 μL of this culture was mixed with 3 mL of soft-LBA (0.75% agar) and plated over a 20 mL bottom layer of 1.5 % LBA on a petri dish...., , # Phage-antibiotic synergy: cell filamentation is a key driver of successful phage predation

## PATHOGENS-D-22-02110R2 \"Phage-antibiotic synergy: cell filamentation is a key driver of successful phage predation\"

Using single-phage and single-cell techniques, each step of the lytic cycle of phage HK620 was studied in E. coli cultures treated with either ciprofloxacin or cephalexin, two filamentation-inducing antibiotics. In the presence of sublethal doses of antibiotics, multiple stress tolerance and DNA repair pathways are triggered following activation of the SOS response. One of the most notable effects is the inhibition of bacterial division. As a result, a significant fraction of cells forms filaments that stop dividing but have higher rates of mutagenesis.

## Description of the Data and file structure

Data corresponding to the figures in the manuscript are arranged in individual tabs included in the same file Datafile\_figures\_2.xlsx

* Fig. 1b: Radii measurements of phage HK6...