Analysis Of Functional Bacterial Groups In Phenanthrene-degrading Biofilm And Natural River Biofilm

Bacteria prefer to live in the form of biofilm in natural setting and the formation of biofilm has effect on biodegradation of polycyclic aromatic hydrocarbons (PAHs). The acyl-homoserine lactone (AHL), a signal molecue in quorum sensing (QS) system, plays an essential role in the regulation of biofilms formation. The study on the AHL-producing and the PAHs-degrading bacterial groups in biofilms can help to provide the basic information for controlling bacterial degrading-activity by QS based on AHL.This thesis investigated the composition of phenanthrene-degraders in bentonite biofilms by clone library and isolated the AHL-producing bacteria from an urban river biofilm by using culture-dependent method. Based on the analysis and overlap of two functiaonal groups, some AHL-producing PAHs-degrading bacteria were isolated. The main conclusions of this work were drawn as follows:(1) Diverse taxa of bacteria formed biofilms on both of organobentonite (COB) and calcinated bentonite (CB) holders during the phenanthrene biodegradation. with families Sphingomonadaceae and Rhodobacteraceae being major members.100%and-80%dioxygenase genes respectively from COB and CB biofilms were closely related to that of Sphingomonas sp.. COB possessed selective effect to certain functional bacterial group.(2) The presence of AHL-producers was detected in1-60-day river biofilms. Screening for AHL-producers resulted in17Aeromonas spp.,3Pseudomonas spp.,3Ensifer spp. and1Acinetobacter spp.. Among these isolates,6of them were closely related to Ensifer adhaerens, Aeromonas allosaccharophila, Aeromonas jandaei, Psuodomonas panipatensis and Aeromonas aquariorum, and represented novel AHL-producing species, which expanded the list of AHL-producers.(3) One AHL-producing and phenanthrene-degrading bacteria were obtained. The strain was closely related to Sphingobium fuliginia.The phenanthrene removal kinetics of the strain showed the removal rate reached98.4%within3days. GC-MS results revealed that the stain produced C12-HSL...