Functional Genes Diversiyt Of Microorganism Related The Cycle Of Carbon In Red-Yellow Soil In Southern China

Soil is the most important carbon pool of terrestrial ecosystem. Content of soil organic carbon is affected by human and natural factors, while microorganisms play an important role. It participate in the soil organic carbon sequestration and regeneration. Soil is carbon pool or carbon source depends on the carbon cycle in soil microbial community structure. CO2 fixation and the release of greenhouse gases are two important processes of carbon cycle, microbial-related functions involved, and cbbL and mcrA are these two marker genes.In this study, a PCR-based cloning DGGE and sequencing approach was used to investigate the molecular diversity and community structure of all bacteria in four soil samples (unfertilized paddy soil in Jiangxi Province, JX-CK; paddy soil amended with chemical fertilizer in Jiangxi Province, JX-S; vegetable soil in Nanjing City, NJ-V; forest soil in Nanjing City, NJ-F). We also had been investigated the molecular diversity and community structure of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase(cbbL) and methanogen connecting with the Carbon cycle.The microbial biomass of two type of soils was compared in spread plate method The results showed that:(1) numbers of soil bacteria and actinomycetes in two samples of the red soil in Jiangxi was lower than the two samples in Nanjing while fungi is higher than them.The microbial biomass of the red soil is somewhat lower generally;(2) The microbial biomass of vegetable soil in Nanjing and Jiangxi rice soil is lower than the control group which indicate that the microbial biomass had negative correlation with the amount of the organic adding in soil.We studied the microbial community structure of the yellow-brown soil in Nanjing city and the red soil in Jiangxi by DGGE.Aanlysis of DGGE fingerprint revealed that the richness of bacteria in two soils were relative high.The diversity of microbial community is higher in red soil and there existed great difference of microbial popution between two type of soils.The dominant microflora of the red soil was more concentrative than that of the yellow-brown soil. The dominant microfloras were changed when the forest land was reclamated into vegetable plot.The influence degree of microbial community in four soil samples manifested as soil types>utilization types>fertilization modes.We obtained 38 OTUs by constructing four cbbL gene libraries of two type soils. The two samples of Jiangxi rice soils had the same dominant OTUs,while the dominant microflora of the forest land in Nanjing was different from the vegetable plot.The coverage C of four libaries was between 94.12% and 98.46%.The cbbL gene diversity indexes of the red soil were somewhat higher than that of the yellow-brown soils and The cbbL gene diversity indexes has negative correlation with the amount of the organic manure adding in the yellow-brown soil. The similarity of four libraries was very low which indicated that the distribution of cbbL gene in soil was more sensitive to environmental factors.We found the cbbL gene widely distributied in soil microorganisms in the class level by phylogenetic analysis of cbbL gene sequences with neighbor-joining method.The cbbL gene primarily distributied in algae including cyanobacteria and chlorophyta,and also in chemoautotrophic bacteria which included thiobacillus and nitrobacter.Chlorophyta in which cbbL gene distributied was the dominant microflora in Nanjing forest land.When the land was reclamated into vegetable plot,the dominant microflora changed into nitric bacteria.CbbL gene dominantly distributied in cyanobacteria in Jiangxi rice soil. Appling inorganic fertilizer would increase proportion of chlorophyta as the dominant microflora, while cyanobacteria as the sub-group changed into nitrobacter.In order to understand the community structure of methanogens in two type of soils.Four mcrA gene libraries were constructed (NJ-F, NJ-V, JX-CK, and JX-S). Total 225 mcrA gene clones were screened and grouped into 13 clusters by RFLP analysis. The libraries can represent the community structure of methanogens in soil.The index of Evenness of four mcrA gene libraries was low,and existed the dominant methanogens microflora which was uncultured.Methanobacterium formicicum and Methanobacterium subterraneum play important roles in Nanjing vegetable land and Jiangxi rice soil.The similarity of four libraries was about 50%.The diversity indexes of four was all low and the differences of them was insignificant.