The lysed cell solution was then centrifuged for 12 min at 13,200 rpm at 4 °C (5415 D, Eppendorf, Hamburgh, Germany). An aliquot of 10 µL of the supernatant was used in a Bradford assay (23246, Thermo Fisher, Pittsburgh, PA, USA) to quantify the cell number (OD=595 nm). A calibration curve between known cell numbers (EVE, NanoEntek, Seoul, South Korea) and the Bradford assay signals was prepared to elucidate cell numbers in the lysed samples.