| With the rapid development of molecular bio-techniques and its wide application in microbial ecology and environmental microbiology, it promotes the development of metagenomics which study on the uncultured microorganisms in the environment. Metagenomics provides a powerful tool to study on the uncultured microorganisms in the complex environmental habitats, it gets started from extracting DNA from the environmental samples, then cloning it into a suitable vector, and introducing it into the host cell, after then selecting out the transformants and sequencing. Metagenmics has been applied to many environmental samples in several yeas, such as the oceans, rivers, lakes, soil, extreme environments, the human mouth and gastrointestinal tract, showing significant value in various areas including medicine, environmental remediation, biotechnology, agriculture.In recent years, as the popularity of metagenomics methods in microbial community structure and diversity of rivers and lakes, studies on the microbial of bottom sluge and water are also increasing. There is a close relationship between the microbial of bottom sluge and water, which constitute the entire ecosystem of the lakes, as a result of this, there is an effect on the growth of the crabs in different lakes. Crabs in Yangcheng lake in Suzhou are the best breed of all the species, and compared with Yangcheng lake, the quality and popularity of crabs from Tai lake are not comparable. In this research, molecular bio-technologies were used to analyse the difference between the two kinds of crab in Yangcheng and Tai lake in microbial perspective.The bottom sluge and water sample from Yangcheng Lake and Tai Lake in the same place were used as a basis in the study during different seasons, beside these, the crabs from the two lakes in autumn were also used for the comparative study. Different kits were used to find out a better way to extract genomic DNA of crab guts. Meanwhile, PCR amplification conditions were optimized to find the optimal conditions for PCR amplification, and genomic DNA extracted from the bottom sluge and water samples of Yangcheng and Tai Lake. Terminal restriction fragment length polymorphism technology was used to analysis the microbial diversity and community structure of all the different samples, and SPSS software was also used to analyse the correlation between the flora of the lakes and crab guts.The results showed that the optimal amplification conditions were 25μL PCR system, 30 cycles and the annealing temperature was 55℃, there was no non-specific amplification and primer dimer in the amplification conditions, which amplified the brightness of the brightest bands. Microbial diversity of the bottom sluge and water samples in Yangcheng Lake was superior to Tai Lake in different seasons which peovided a better environment for crabs in Yangcheng Lake. There was a significant difference between the crab gut microbiota in two lakes, moreover, the female crab and koenigskrabbe gut microbiota in the same lake were also different. According to the analysis by SPSS, it showed that there was a significant correlation between the crab gut microbiota and the flora in the environment where the crab grew up. The correlation between the crab gut microbiota and the flora in Yangcheng Lake was higher than it was in Tai Lake, which indicated that the bottom sluge and water had a greater influence on the crab breeding in Yangcheng Lake. The conclusion could be drew for these, the microbial diversity and community structure had some influence on the gut microbiota of crabs which grew up in different freshwater lakes, and there was a positive correlation between these, so we should protect the microbial diversity of the freshwater lakes. |
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