Investigating The Influence Of Deterministic Processes On Community Assembly And Succession Using Synthetic Microbial Systems

The assembly of microbial community has always been the core content of environmental microbiology research,and has a long history in the research of environmental microbiology.Research on the assembly of microbial communities is essential to explain the coexistence of species and the maintenance of species diversity.In the process of deterministic,the main considerations include the adaptation of environmental selection pressure and the broad microbial interactions.Current research on deterministic processes mainly focuses on top-down sequencing-based methods,and this method cannot determine how specific factors such as interactions and environmental conditions in deterministic processes affect community assembly.Based on the bottom-up cultivation method,the use of synthetic microbial community research community assembly can separate these factors separately and study them quantitatively through a simple system.In this paper,a synthetic microbial community is composed of 20 strains of bacteria isolated from the same soil environment on the bank of Weiminghu Lake in Peking University.The four carbon sources of glucose,citric acid,sodium acetate and serine were selected as the different environmental selection pressures of the microbial community,and the influence of the deterministic process on community succession was studied.The main results are as follows,(1)In order to determine the growth difference of each strain under different environmental selection pressures,20 strains of bacteria were cultured separately.It was found that the growth difference of each strain was smaller in glucose,serine and sodium acetate,while the growth difference was larger in citric acid.Under the same environmental selection pressure,the adaptability of different strains is different,but most strains can grow faster,and a small number of strains grow slower.Under different environmental selection pressures,the same strains will also show different growth rate differences,most strains have little difference,and a small number of strains have big differences.(2)Through quantitative analysis of the defined interaction coefficient ?,under rich nutrient conditions(such as glucose and citric acid),inhibition dominates the pairwise interaction,while in relatively harsh environmental conditions induces pairwise microbes promote relationships to cope with environmental pressures.Next,through the analysis of the defined strain interaction force F,it was found that the strain interaction force is related to the growth rate of the strain itself.The fast-growing bacteria have a stronger inhibitory effect,but they are different under different carbon source conditions.In citric acid and sodium acetate,slow-growing strains also have a strong inhibitory effect.(3)In order to study the change of species diversity in the process of community succession,the complete seed bank composed of 20 strains of bacteria was subcultured 6 times.The results of ? diversity and PCA cluster analysis showed that the diversity of communities under different selection pressures changed differently.Citric acid is a strong selection pressure,and the remaining carbon sources are weak selection pressures.Strong selection pressure accelerates the loss of diversity,and under weak selection pressure the loss of diversity is slow.Further analysis found that the diversity of the community is more likely to be maintained through interaction,and the structure of interaction within the community may serve as a stable force for species diversity.(4)Further study the relative contribution of interaction force and environmental selection pressure to community assembly during community succession.Under the condition of strong overall interaction force(glucose and citric acid),microorganisms with strong growth ability and interaction force of single bacteria have advantages.The overall interaction force is weak(serine),which promotes more situations,and the interaction force has a more important driving effect on community assembly.When the overall interaction force is at a medium level(sodium acetate),or when inhibiting and promoting each half,the difference in growth between microorganisms has a more important driving effect on community assembly.Through the above research,this paper describes the impact of two deterministic processes of environmental selection pressure and species interaction on community succession through artificially constructed microbial systems.Diversity formation mechanisms help.