The Role Of Quorum Sensing On The Colonization Of Pseudomonas Sp. HF-1and Its Application Potential

Based on the quorum sensing theory, a series of experiments focuing on the bioaugmentation of Pseudomonas sp. HF-1were carried out in this study. The study can provide theoretical and technical help to the repairment of tobacco waste pollution. The results were as follows:(1) By exogenous addition of N-hexanoyl-homoserine lactone (C6-HSL), N-3-oxo-hexanoyl-homoserine lactone (3-oxo-C6-HSL) and N-3-oxo-octanoyl-homoserine lactone (3-oxo-C8-HSL), it could be found that they all had impact on biofilm formation in strain HF-1. Swarming could be induced by20nmol C6-HSL and40nmol3-oxo-C6-HSL, while extracellular polymeric substances (EPS) formation was induced by40nmol3-oxo-C6-HSL,40nmol C6-HSL and20nmol3-oxo-C8-HSL, and biofilm formation was induced by10nmol C6-HSL and40nmol3-oxo-C8-HSL.(2) By exogenous addition of porcine kidney acylase I, it could be seen that quorum sensing plays an important role in the colonization of HF-1and the construction of its bioaugmented system. The amount of3-oxo-C6-HSL, C6-HSL and3-oxo-C8-HSL in the quorum quench reactors were below30nmol,10nmol and8nmol, independently, which could not reach their thresholds for EPS formation and biofilm formation of strain HF-1. Accordingly, the biofilm formation and colonization of strain HF-1were hindered. Definitely, a lower efficiency of nicotine and total organic carbon (TOC) removal was observed in the failure bioaugmented system.(3) By analysis the attenuation of N-acyl-homoserine lactones (AHLs) under different environment conditions, it could be found that3-oxo-C6-HSL and3-oxo-Cg-HSL were much more stable than that of C6-HSL and N-octanoyl-homoserine lactone (C8-HSL), and the half-lives of them were1573.58h,2351.39h,43.67h and301.38h, independently. The stability of AHLs was dependent on the pH value, temperature and salinity. High pH value (above8), temperature (>30℃) and salinity (above2%) led to the attenuation of AHLs. Those remind us that the exogenous addition of AHLs may have little effect on the bioaugmention of strain HF-1. (4) The AHLs secretion by HF-1under different environment was examed. It could be found that when culture conditions were set at25℃, pH5-6,3%inoculum,1.5g/L nicotine and1%NaCl, AHLs were released at levels sufficient for quorum sensing in strain HF-1for swarming and EPS formation. That’s to say, the low pH value (pH5-6) was good for the colonization of strain HF-1and the high pH value (around8) was beneficial for the stable operation of bioaugmented reactor.(5) According to the best environmental conditions for biofilm formation of strain HF-1in pure culture, an optimization reactor was operated (pH5.5for3d and pH8for the rest). The thresholds of AHLs for biofilm formation and EPS production were reached in the system. Aerobic granular sludge was formed with the partical size of527μm and the integrity coefficient of52.49±0.54%. The nicotine and TOC removel were above90%and55%, independently, which made the start-up and operation of bioaugmented reactor controllable.