Studies On Sporosarcina Pasteurii Induced Mineralization And Its Mechanism

The current research on the application of microbial induced mineralization mainly focuses on macroscopic analysis and improvement of the effect on engineering applications.But the corresponding research on the mechanism of microbial mineralization is seriously lagging behind which leads to the instability and uncontrollability of the effect of the current application of large-scale mineralization technology.This research took the urgent need of reef maintenance and reinforcement of the South China Sea reefs as the research background,addressed the cost and benefit of Sporosarcina pasteurii culturing.Combined with the growth test experiment and bioinformatic analysis,the main nutrient sources necessary for bacterial growth were investigated.The key factors that the mineralization products have cementing ability and affect the cementing ability were also explored.To resolve the problem of instability and uncontrollability in mineralization applications,the expression and regulation rules of urease and the structures of urease gene clusters,were studied from the perspective of mineralization mechanism by using bioinformatic methods.First of all,the study of the nutrient source of Sporosarcina pasteurii was carried out to address the undefined nutritional requirements of Sporosarcina pasteurii.We found that Sporosarcina pasteurii could grow only in the presence of ammonium or urea through constantly groping for bacterial culture conditions by controlling the variables,indicating that ammonium or urea was the necessary nitrogen sources for Sporosarcina pasteurii.On the other hand,experiments confirmed that compounds such as yeast extracts or peptone could provide carbon source for Sporosarcina pasteurii,and glucose could not provide carbon source for Sporosarcina pasteurii.In view of the limitations of growth testing,we analyzed the gene expression changes of Sporosarcina pasteurii under four different culture conditions by bioinformatic methods which based on transcriptome sequencing experiments.The result further confirmed that ammonium and urea were the nitrogen sources,and amino acid substances were the carbon sources,and Sporosarcina pasteurii could not use glucose due to the lack of hexokinase.Secondly,in view of the instability of the cementation effect of the mineralization products of Sporosarcina pasteurii,the factors that influenced mineralization effect were investigated.The relationship between the crystal form of the mineralization products and the mineralization cementation effect was analyzed.Various material factors that may affect the cementation ability of mineralized products were studied,and the causes for the change of cementation ability were analyzed according to the composition change of crystal forms of mineralized products.The results showed that yeast extracts and ammonium chloride were the optimal compositions in the medium,and calcium chloride was the optimal calcium source in the cementing solutions.Moreover,there was no significant correlation between the cementing ability of mineralized products and the crystal forms of the products in the experiments.First of all,to resolve the uncontrollability and heterogeneity in the application of Sporosarcina pasteurii induced mineralization,this paper focused on the regulation mechanism of Sporosarcina pasteurii urease expression and explored the factors affecting urease expression by bioinformatic methods and molecular biology methods.The analysis from the aspect of mineralization mechanism showed that urease had the optimal expression level and activity in a stable and appropriate pH range.The gene cluster structure of urease was analyzed,and the structure of urease with double operon in Sporosarcina pasteurii was found and verified for the first time.The discovery of the above findings contributes to the solution of the key problem of regulation of mineralization function in Sporosarcina pasteurii.These results will greatly promote the application and expansion of induced mineralization technology under more conditions.The microbial catalytically induced bioactive materials can also be used in biomedical engineering fields such as bone tissue regeneration and artificial prosthesis,which will provide new ideas for the preparation of biomedical materials.