Study On Interaction Mechanism Between Bacillus Atrophaeus And Uranium, Chromium

As a low cost, efficient and environment-friendly process, microbial remediation technology for heavy metal and nuclide pollution becomes a hotspot research recently.In order to study the effects of microorganisms on U(VI), Cr(VI) removal and interaction mechanism of above two, two strains of Bacillus atrophaeus(ATCC 9372 and Ua) were chosed as research materials firstly. GM technology was used to test the function of gene Yti B, gene Yth A, gene Pho N on removing U(VI), Cr(VI) secondly.The expression mechanism of two stains dealing with Cr(VI) stress was analyzed by RNA-seq finally. The main results are as follows:(1)The removing ability of microorganisms was related to its tolerance to heavy metals was found out by researching the differences of removal and capacity of tolerance to U(VI) between ATCC 9372 strain and Ua strain. There is a significant difference of removal effects to heavy metals among same species of microorganisms.The removal effect of ATCC 9372 and Ua are basically the same when the concentration of U(VI) was less than 80mg/L; The removal rate of ATCC 9372 strain reached 93.33% as the concentration of U(VI) reach 120 mg/L which was 20% higher than Ua strain; When the concentration of Cr(VI) was less than 20mg/L, the removal effect of ATCC 9372 and Ua are almost the same; A huge different of removal effect between two strains appeared as along as the concentration of Cr(VI) reached to40mg/L. The differences of removal ability between ATCC 9372 and Ua may be decided by the source of the Ua strain and the different removal capabilities of microorganisms.(2)In order to explore the removal effect to U(VI), Cr(VI) of gene Yti B, gene Yth A, gene Pho N. Bacillus atrophaeus ATCC 9372 strain which has a good tolerance and removal capacity to U(VI), Cr(VI) was chosed as host strain, p BS-E DNA as expression vector, the shuttle expression vector strategy was used to put the target genes into host strain. The GM technology can provide material for the following studies.(3)By studying the removing effect to U(VI), Cr(VI) of ATCC 9372-Yti B strain,we found the removal rate to 120mg/L U(VI) of ATCC 9372-Yti B strain declined7.55%, the removal rate to 40mg/L Cr(VI) declined 11.95%, which reflected that gene Yti B can inhibit the function of removing U(VI), Cr(VI).(4)By studying the removing effect to U(VI), Cr(VI) of ATCC 9372-Yth A strain,we found the removal rate to 120mg/L U(VI) of ATCC 9372-Yth A strain declined7.43%, the removal rate to 40mg/L Cr(VI) declined 23.19%, which reflected that gene Yth A can inhibit the function of removing U(VI), Cr(VI).(5)By studying the removing effect to U(VI), Cr(VI) of ATCC 9372-Pho N strain.we found the removal rate to 120mg/L U(VI) of ATCC 9372-Pho N strain increased7.43%, the removal rate to 40mg/L Cr(VI) increased 23.19%, which reflected that gene Pho N can promote the function of removing U(VI), Cr(VI).(6)Bacillus atrophaeus ATCC 9372 strain and Ua strain which had been treated with 40mg/L Cr(VI) for 48 h were analyzed by RNA-seq. The main results are as follows: ATCC 9372 strain has 197 up-regulated genes, 196 down-regulated genes,3793 genes did not change significantly; Ua strain has 228 up-regulated genes, 144down-regulated genes, 3814 genes did not change significantly. The GO annotation showed that genes involved in the BP appeared large different expression, which reflected that regulating metabolism was the main reaction of microorganisms to response to heavy metal stress. The KEGG pathways showed that Genes involved in complex metabolic pathways in cells, which means that the functions of genes were not only decided by themselves, but also the pathways which they involved in.In conclusion, significant difference of removal capacity of heavy metals appears between similar microorganisms. The functions of genes were not only decided by themselves, but also the pathways which they involved in was reflected from the results of GM technology and KEGG metabolic pathways. Metabolic activities were adjusted as the main coping strategy when microorganisms face heavy metal stress.