Studies On The Bacterial Quantity Fluctuation And Flora In Grass Carp Polyculture System

Quantitative and qualitative analyses of bacterial flora associated with water, sediment and intestine are investigated. There were four kinds of models (G, GS, GC and GSC) studied in this research. The main results are detailed as follows:1. The study on heterotrophic bacteria flora associated with the water and sediment was investigated in grass carp (Ctenopharyngodon idellus) polyculture system from May 2009 to Oct. The results from four models showed that the number of heterotrophic bacterial and Vibrio from water increased to peak in Aug. However the number of heterotrophic bacterial and Vibrio from sediment went up to peak in Sep. The number of heterotrophic bacterial in grass carp, silver carp (Hypophythalmichthys molitrix) and carp(Cyprinus carpio) polyculture system(GSC)from water and sediment was significantly higher than that in the other tree models (p<0.05). The number of Vibrio in grass carp and carp polyculture system(GC) and grass carp monoculture model (G) from water and sediment was higher than the other two (p<0.05). Physicochemical parameters influenced the number of heterotrophic bacteria from water and sediment, among which DIN influenced most. Based on the partial sequences of 16S rDNA analysis, 40 genera were identified from water and 32 genera from sediment. The percentage of Vibrio to total heterotrophic bacterial genera in GSC model was the lowest. According to the calculation of Shannon-wiener's diversity index, the diversity of heterotrophic bacterial flora in GSC was higher than that in the other three models (p<0.05).2. The study on the heterotrophic bacteria flora associated with intestine of grass carp, silver carp and carp was investigated in polyculture system from May 2009 to Oct. The results showed that the number of heterotrophic bacterial and Vibrio from intestine rose with months. The number of heterotrophic bacterial in grass carp monoculture mode(lG)from intestine of grass carp was significantly higher than that in the other tree models (p<0.05). The number of heterotrophic bacterial in grass carp, silver carp and carp polyculture system(GSC)from intestine of silver carp was significantly higher than GS model (p<0.05). However, the number of heterotrophic bacterial in grass carp and carp polyculture model (GC) from intestine of carp was significantly higher than GSC model (p<0.05). The number of Vibrio in GSC from intestine of grass carp, silver carp and carp was lower than the other two (p<0.05). Based on the partial sequences of 16S rDNA analysis, 27, 24 and 17 genera were identified from intestine of grass carp, silver carp and carp respectively. The percentage of Vibrio to total heterotrophic bacterial genera in GSC model was the lowest. According to the calculation of Shannon-wiener's diversity index, the diversity of heterotrophic bacterial flora in GSC was higher than that in the other three models (p<0.05).3. The study on the bacteria quantity fluctuation and bacterial community functional diversity in grass carppolyculture system from May 2009 to Oct. The results from three models showed that the number of heterotrophic bacteria and total bacterial count from water decreased followed by increasing. While the number of heterotrophic bacteria and total bacterial count from sediment went up to peak then declined, then rose. The trend of the number of heterotrophic bacteria from intestine was same with that of sediment. The number of heterotrophic bacteria and total bacterial count in grass carp, silver carp and carp polyculture system(GSC) from water and sediment was significantly higher than that in the other tree models (p<0.05). However, the number of heterotrophic bacteria in grass carp monoculture model(G)from intestine was significantly higher than the other three (p<0.05). Physicochemical parameters influenced the number of heterotrophic bacteria from water and sediment, among which DIN influenced most. Biolog examination showed that carbon source utilization and microbial diversity were different among the three models. Multi-function and metabolic ability of bacterial community in GSC model were higher than other models (p<0.05). Finally, PCA of DGGE banding patterns of different microbial community showed that the composition diversity increased as the culture time and two polyculture models'diversity more than single-model's.