Ammonia-Induced Dispersion and Proliferation of Actinobacillus pleuropneumoniae Biofilms

To elucidate the mechanisms by which ammonia induced the dispersion and proliferation of A. pleuropneumoniae biofilms, NH3·H2O was added to biofilms and planktonic bacteria cultured to the log-phase for short-term stimulation and incubation. Subsequently, planktonic bacteria after ammonia stimulation (PK_NH3, the rapidly proliferating planktonic bacteria after ammonia stimulation), bacteria in the biofilm adhered layer (BF_NH3, adhered biofilm) and the supernatant layer (Up_NH3, bacteria dispersed from the BF layer ) were collected, along with the supernatant layer (Up_DspB) and adhered layer (BF_DspB) treated with DspB, and untreated control groups (PK_Con, Up_Con, BF_Con). RNA was extracted for transcriptome sequencing analysis. Overall design: The planktonic cells (PK) of A. pleuropneumoniae 4074, cultured overnight, were inoculated into fresh medium and grown to early-log phase (2 h). Subsequently, 10 mmol/L NH3·H2O was added to the planktonic cells, and the mixture was incubated at 37°C for 2 h. The biofilm-forming cells (BF) of A. pleuropneumoniae were cultured to mid-log phase (5 h) in 12-wells flat bottom cell culture plates. Then, 10 mmol/L NH3·H2O and 2 mg/mL DspB were added separately, and the cultures were incubated at 37°C for 2.5 h. The planktonic and biofilm-associated bacteria were separated.