Study On The Colonization Of A Nicotine-Degrading Bacterium Pseudomonas Sp.HF-1in Activatied Sludge And Its Ecological Mechanisms

In this paper, bioagumented reactors were constructed with an efficient nicotine-degrading bacterium Pseudomonas sp. HF-1to treat tobacco wastewater. The conditions of its start-up were optimizated and the stability of the strain HF-1bioaugmented system was studied. In addation, by comparing the successful and failed reactors during the start-up, the mechanisms of strain HF-1colonization were discussed from the microbial population structure as well as the quorum sensing. The main results obtained in this research were as follows:(1) The inoculum amount of strain HF-1played an important role in its colonization. An inoculum size of1.10mg/g (cell/sludge, dry weight) made the greatest performance of its colonization and contaminants removal. The initial pH of tobacco wastewater was another important factor that affected the colonization of strain HF-1. Under the conidition of pH7.0, the colonization of strain HF-1and the performance of contaminants removal both reached its best, while when the pH became alkaline, the performace deteriorated. The colonization of strain HF-1was less affected by nicotine load up to1200mg/L, and reached its best under1000mg/L nicotine load, however, when the load exceeded1000mg/L the efficiency of total organic carbon (TOC) removal declined.(2) The bioaugmented reactors with the colonization of strain HF-1showed a strong resistance to nicotine shock loading up to2500mg/L. There was no adverse impact on the colonization of strain HF-1. On the contrary, the activity of gene hsp, which was a key gene of nicotine degradation, was improved. Although the microbial community appeared oxidative damage under nicotine shock load, it can be recovered to its initial level after7d and the microbial community structure barely changed. Meanwhile, the efficiency of nicotine and TOC degradation can be returned to its initial levels within2-4d.(3) The mechanism of strain HF-1colonization was preliminary investigated using a combination of polymerase chain reaction and denaturing fradient gel electrophoresis (PCR-DGGE). DGGE fringerprint profiles showed significant differences in microbial structure among the reactor1-2which was successfully bioaugmented and the other reactors with different inoculum contents. Their similarity was only58%. What’s more, the Shannon-Wierner index of1-2was3.06, significantly higher than others. It suggested that the colonization of strain HF-1in activated sludge could change its microbial structure and increased its microbial diversity. The release pattern of autoinducers for quorum sensing was also investigated. During the period of HF-1inoculation, AI-2was significantly increased in the successful reactors. When inoculation of strain HF-1was stopped, the content of AI-2decreased and leveled out in all systems. Notably, the content of both short-chain and long-chain AHLs were significantly increased in failed bioaugmented reactors, but no increase in successful ones. The results indicating that AI-2mediated bacterial communication played an important role in the colonization of HF-1.