The Effects Of Exogenous Lignocellulose On Bacterial Community Structure In Soil

The microbial degradation of lignocellulose is one of the important processes in the carbon cycle of ecosystem, which directly or indirectly affect the diversity of soil microorganisms, but the mechnism of regulation and control is still remain unclear..In this paper, the soil, on which many fallen leaves had accumulated all year round, was selected as the studying object. After exogenous lignocellulose (disposable chopsticks) were added into the soil, total DNA of microorganism in the soil both close to the chopsticks at 2cm and 10cm distance was extracted directly after 21-day and 63-day induction. Then the clone library of 16S rDNA of bacteria in soil was established, and the characteristics of structural changes and regulation of soil bacteria floras at different levels under the induction of lignocellulose were compared and analysed. The aim of this study is to reveal the impact of lignocellulose degradation process on the microorganisms existed around the chopsticks. This study can deepen our understanding on the interaction between bacteria and the corresponding soil environment.The results showed that after 21-day induction, there were not obvious changes occurred for the soil samples near chopsticks (0cm-2cm), the major components of bacteria are still Pseudomonas, Streptomyces, and Bacillus genus, the number of nitrobacterias also increased.While for the soil samples at a distance of 10-12cm to the chopsticks, the above three genus of bacteria were still the predominant ones, but the number of Streptomyces overpassed that of Pseudomonas. In addition, the number of pathogenic Bacillus including Shigella , Staphylococcus and Acinetobacter increased. After 63-day induction, the Pseudomonas in the soil close to chopsticks (0cm-2cm) was the dominant genus, while at a distance of 10-12cm to the chopsticks, Shigella was the dominant genus, Pseudomonas was on the second position. This might be associated with the change in the carbon cycle caused by the consume of lignin.Comparasion of the CMC and FPA enzyme activities between mixed culture of different strains and single-cultured strains and consortia at 20℃were also did, in order to screen degrading consortia with high effectiveness. Among those consortia, bacteria strain DS6 mixed with two fungi strains LF1 and LF3 had the highest degrading efficiency, which could be used into practice.