Studies On The Bacterial Community Structure And Function In Grass Carp Polyculture System

Study on the bacteria quantity fluctuation, dominant bacteria and bacterial communityfunctional diversity associated with the water, sediment was investigated in grass carp(Ctenopharyngodon idellus) polyculture by using the traditional culture isolation method,fluorescence in situ hybridization, Biolog-Eco micro plate method, denaturing gradient gelelectrophoresis (DGGE) method. The results could provide a theoretical basis for thestructural optimization in different grass carp polyculture mode. Specific research resultswere as follows:1The study on bacteria in water and sediment that may play an important role inbiogeochemical processes such as carbonization-metabonization, nitrogen-cycling，H2S-producing and phosphate-cycling associated with microbial quantity change and thequantity of water，was investigated in polyculture system from May20,2011to Oct15,2011.The results show that：（1） In grass carp polyculture system the number ofstarch-hydrolyzing is more than that of protein-hydrolyzing. The number of thedecomposition of the carbon containing organic compounds (starch, cellulose) bacterial inwater are generally lower than the number of bacteria in sediment.（2）On nitrogen-cyclin，the number of nitrifying bacteria, nitrite bacteria is higher than the denitrifying bacteria. Onphosphate-cycling，there is no difference between the number of using organic phosphatebacteria and inorganic phosphate. And the number went up to peak in Aug. The number ofparticipating in the phosphorus cycle (decomposition of organic and inorganic phosphorus)bacterial in water is generally higher than the number of bacteria in the sediment.2The study on heterotrophic bacteria and vibrio flora associated with the water, sedimentof grass carp, was investigated in polyculture system from May20,2011to Oct15,2011. Five polyculture system included grass carp, silver carp and carp. By using BIOLOG ECOmicroplate， microbial community metabolic changes in water and sediment were alsostudied. The results show that the amounts of heterotrophic bacteria, Vibio in water changerather greatly during the cultural period.The number of heterotrophic bacteria from waterexhibited different tendency with seasons in the five models. The number of heterotrophicbacteria from sediment exhibited similar descending tendency with seasons.However, thenumber of Vibio in grass carp monoculture model（G）from water was significantly higherthan the other four(p<0.05) in the later period and went up to peak in July.Biologexamination showed that carbon source utilization and microbial diversity were differentamong the five models.In water, Multi-function and metabolic ability of bacterialcommunity in GS, GSC models were lower than other models (p<0.05).Insediment,Multi-function and metabolic ability of bacterial community in GSC1, GSC2models were higher than other models (p<0.05). In Water， Shannon index and McIntosh(U) of the group G were significant higher than those of GS, GSC1, GSC2group. Insediment,Shannon index and McIntosh (U) of group GSC2is maximum.3. Study on dominant bacteria in sediment of grass carp, was investigated in polyculturesystem from May20,2011to Oct15,2011. In the early, late, late breeding differentperiods，the17dominate DGGE bands that were successful cloned and sequenced are allunculturable bacteria. The results show that: The least abundant bacterial composition wasfound in GSC1、GSC2in Oct. The main microbes represented by12main bands in DGGEgel were closely related to Actinobacteria、 Alpha-Proteobacteria、 Bacteroidetes、Cyanobacteria. Based on the UPGMA cluster analysis of the monthly samples.In October,G group，GS group of bacterial community diversity has higher similarity.In sediment, the results show that: microbial community composed mainly of alphaProteobacteria、beta Proteobacteria、Bacteroidetes and Chloroflexi in grass carp polyculturesystem. This study showed that the number of dominant bacteria in different models ischange as the time, Based on the UPGMA cluster analysis of the monthly samples,Thebacteria communitity in Aug show relatively high similarity. The GSC1and GSC2groupsimilarity coefficient is in the highest similarity.