Preparation of bacteria
Specific bacterial growth curves, i.e. correspondence between
the optical density at 600 nm (OD600nm) and colony-forming units
(CFU), were developed for each strain. The bacteria were collected
when their OD600nm during the log phase corresponded to 109 CFU/
mL. The harvested cells were washed twice with sterile phosphate
buffered saline (PBS) and centrifuged at 9000 g for 10 min.