Formaldehyde (Sigma) was added to the cultures to a final concentration of 1% (v/v) and the mixture was incubated at room-temperature with shaking for 30 min. Afterwards, glycine was added to a final concentration of 125mM and further incubated at room-temperature with shaking for 10 min. Samples were resuspended in 300µl IP buffer (50mM Tris/HCl pH 7.5, 5mM EDTA, 150mM NaCl, 25mM sucrose, 1µg mL-1 lysostaphin, Sigma, 0.3 µg mL-1 RNase A, Sigma, and 1 tablet of cOmplete protease inhibitor cocktail, EDTA free, Roche, per 10mL of buffer) and incubated at 37°C for 1h with shaking. Afterwards the samples were cooled on ice, TritonX-100 was added to a final concentration of 1% (v/v) and they were vortexed. Samples were then sonicated using a Bioruptor Plus bath sonicator at 4°C using 50 cycles of alternating 30s on and 90s off in the high-power mode followed by centrifugation at 20000xg for 10min at 4°C. Libraries were constructed using the NuGEN Ovation ultra low library preparation kit following the manufacturers instructions.