Research On Diversity Of Microbial Community Constructure In MBRs

In this study, aiming emphatically at the characteristic of the membrane biological reactor(MBR) wastewater treatment process, the microbial community structure of the process was researched with molecular biological method, such as polymerase chain reaction(PCR) and denaturing gradient gel eletrophoresis(DGGE). Baed on this, the differences of the microbial community structure between the four MBRs treating different wastewater was studied.The genomic DNA of microbial communities was extracted directly after cell lysis with chemical agent. After the 16S rRNA genes(V3 region)were amplified using the universal primers, These PCR products were separated by DGGE. Then the DNA finger printings of the sludges samples were taken pictures, which represent the charecterstic of the microbial community structure of the different sludge samples.The results show that the hign quality genomic DNA can be obtained with the method of chemical lysis—Tris saturate phenol(Phenol:Chloroform:Isoamyl alcohol =25:24:1) extract—purification of the genomic DNA purify kit.The change was greatly taken place on the 4th-5th day after sludge was inoculated in the lab-scale MBR . In the process of experiment, some kinds of populations have been stably possessing high preponderant degrees, as well as the primary communities died out, and the second microbial communities increased. Cluster analysis of DGGE by UPGMA divided the total time of experiment into three periods, this results showed that the dynamic changes of microbial community construcure were responsible to different period during the opertation of MBR. Nested PCR of 16S rDNA fragments specific to ammonia-oxidizing bacteria (AOB) and DGGE were used to explore the succession and shifts of the ammonia-oxidizing community. Some kind of dominant population in AOB have been existing in the community structure during the experiment of lab-scale MBR. Speed of shift of AOB community was slower than of total bacterial community.In the profile of DGGE,there exist some common bands and also specific bands. The common bands indicate that some microorganisms coexist in four MBRs. The specific bands show that different MBR own specific microorganisms. Furthermore in the four MBRs, the common microorganisms have the different preponderant degrees. The specific microorganisms were gradually become to the predominant communities after a long period of cultivation and acclimatization because of the different inlet quality.It was the same climax communitis of AOB existed in all MBRs that played an important role in the removal of ammonia nitrogen. The inlet quality had the major effect on the growth of AOB.