Diversity Of Rhizosphere Microbial Community Of Plants Petroleum-conta Minated Saline-alkali Region In Daqing

This study focused on the plant rhizosphere microbial community in oil-contaminatedsaline soil in Daqing region. By using dilution plate method, BIOLOG microplatemethod, denaturing gradient gel electrophoresis (DGGE) analysis and soil enzymeanalysis, we comprehensively investigated the effects of saline and oil on number,function and structure of rhizosphere microbial community in this region. The resultsare as follows:1. The number of microorganisms was analyzed by using dilution plate method. Theresults showed that Xanthium, Puccinellia tenuiflora and Suaeda salsa have moremicroorganisms under saline condition than those under oil condition; whereasKalimeris indica, Artemisia scoparia and Phragmites communis have moremicroorganisms under oil condition than those under saline condition. By comparisondata from2012and2013, we observed a consensus pattern in number for three kinds ofmicroorganisms.The number of culturable bacteria from high to low was as follows:Phragmites communis> Melilotus suaveolens> Artemisia scoparia> Xanthiumsibiricum> Puccinellia tenuiflora> Saussurea amara> Suaeda salsa> Kalimerisindica; the number of culturable fungi from high to low was as follows: Melilotussuaveolens> Saussurea amara> Artemisia scoparia> Xanthium sibiricum> Kalimerisindica> Puccinellia tenuiflora> Suaeda salsa> Phragmites communis; and the numberof culturable actinomycetes from high to low was as follows: Melilotus suaveolens>Artemisia scoparia> Xanthium sibiricum> Phragmites communis> Saussurea amara>Puccinellia tenuiflora> Suaeda salsa> Kalimeris indica.2. The function of microbial community was studied by using BIOLOG microplatemethod. The results showed that, under saline condition, the highest and lowestmetabolic capacity were observed for Saussurea amara and Suaeda salsa, respectively;under oil condition, the highest and lowest metabolic capacity were observed forXanthium sibiricum and Suaeda salsa, respectively. Different plant communities of soilbacteria metabolize carbon substrates main ingredient under salinity stress environmentwere analyzed. The results showed that Suaeda salsa, Puccinellia tenuiflora, Saussureaamara were significant different with other plants. Different plant communities of soil bacteria metabolize carbon substrates under the main component of oil pollution of theenvironment were analyzed. The results showed that Suaeda salsa, Phragmitescommunis and other plants were significant different. The same kind of plants understress conditions and soil salinity substrate carbon metabolism of bacterial communitiesunder the main component of oil pollution of the environment are analyzed. The resultsshow that the difference in the ability of the two conditions of soil bacteria on carbonsubstrate utilization is significantly different between Phragmites communis andArtemisia scoparia, no significant difference was observed among Puccinelliatenuiflora, Kalimeris indica and Suaeda salsa.3. The structure of rhizosphere microbial community was analyzed for different plantspecies by DGGE methods. The plant species within the same family tends to have thesimilar microbial community, e.g., Xanthium sibiricum, Saussurea amara and Artemisiascoparia, Puccinellia tenuiflora and Phragmites communis. By comparing the bandpatterns under conditions of saline and oil, we found that band#3,#5and#6werespecifically accumulated in a plant species under the saline condition, indicatinginhibitive roles of oil stress to these bacterial species. The band#14was specificallyenriched in Kalimeris indica under oil condition, indicating the stimulated roles of oilfor this bacterium. A total of14bands were cut, sequenced, and subsequently submittedto NCBI for BLAST test. The results showed that the bands#1,#2,#3,#5,#6,#7,#8,#9and#10were belonged to Acidobacteria; whereas bands#4,#11,#12and#14werebelonged to Proteobacterium. The only one bacterial species was found inPseudomonadales for band#10.4. The activity of soil enzymes was analyzed by using enzymatic assay. The resultsshowed that under saline condition, the highest enzymetic activity of soil urease forSaussurea amara, and the lowest enzymatic activity for Puccinellia tenuiflora wasobserved. By comparing the enzymatic activities of soil urease under saline and oilconditions, we found that the enzymatic activity was decreased after oil stress for alltested plant species. The results of enzymatic assay for soil dehydrogenase showed thatSaussurea amara have the highest activity level and Puccinellia tenuiflora have thelowest activity level in the corresponding rhizosphere region. By comparing theenzymatic activities of soil dehydrogenase under saline and oil conditions, we foundthat the enzymatic activity was increased after oil stress for all tested plant species. The enzymatic assay for soil invertase showed that Melilotus suaveolens have the highestactivity level and Puccinellia tenuiflora have the lowest activity level. By comparingthe enzymatic activities of soil invertase under saline and oil conditions, we found thatthe enzymatic activity was increased after oil stress for all tested plant species. Bycomparing data obtained from2012to2013, we found that a number of plant specieshave similar patterns of soli enzymatic activity under saline condition. For soil urease,the level of enzymatic activity from high to low was Artemisia scoparia, Melilotussuaveolens, Xanthium sibiricum, Suaeda salsa, Puccinellia tenuiflora; for soildehydrogenase, the level of enzymatic activity from high to low was Melilotussuaveolens, Artemisia scoparia, Kalimeris indica, Phragmites communis, Puccinelliatenuiflora; for soil invertase, the level of enzymatic activity was Melilotus suaveolens,Kalimeris indica, Artemisia scoparia, Suaeda salsa, Puccinellia tenuiflora.