From Rocks To Soils: Examples Of Succession And Ecological Function Analysis Of Microbial Communities

In the life system of the earth,the evolution and development of microbes has a profound effect on all aspects of rock weathering,soil genesis,the formation of mycorrhizae,and maintenance the environmental stabilization of plant root.It will be of great significance to explore the interaction between microbes,which will accelerate our understanding of the process from biological weathering to soils,maintenance the soil environment mediated by plants--fungi--bacteria,as well as the bioremediation in contaminated areas.We explored microbial communities taking the sandstone of Xianlin,Nanjing for an example.And we collected the samples from bare sandstone to different sandstone or soils covered by different organisms by using the strategies of space instead of time.We examined the microbial diversity of different samples by the Next Generation Sequencing.The main results showed that there were fewer types of bacteria in the bare rock and the rock with lichens and mainly contained autotrophic bacteria,such as Cyanobacteria and Chloroflexi groups.At the same time,there were quite a few Proteobacteria and Ascomycota groups and Ascomycota had an absolute advantage in the lichen stage(89.30±0.03%)which may arised from the symbiotic structure between Ascomycetes and Cyanobacteria or Chlorophytes.When the vascular plants appeared in the rock,the observed_OTUs of bacteria and fungi increased significantly and the composition of bacterial groups became diversified and complicated perhaps in order to adapt to ecological functions.The roles of bacteria had gradually changed,which from vanguards of weathering rocks to decomposers in soils and maintainers of various ecological relationships.And the bacteria,such as Bacteroidetes,and Nitrospirae,and the fungi,such as Basidiomycetes,zygomycetes,and Glomus emerged in the stage of the vascular plants.These fungi were capable of forming mycorrhizae with the fine of plants which accelerated the weathering of rocks,facilitated soil genesis and promoted plant growth.In addition,the total organic carbon content of soils was linearly related to observed_OTUs of bacteria(R2=0.65,p<0.05).The formation of soil was a long-term slow process,which depends on a combo of plants--fungi--bacteria.The evolution and development of plants in terrestrial ecosystems indirectly contributed to the two major development trends of fungi,namely,the mycorrhizal fungi and saprophytic fungi.In this study,we detected endophytic bacteria within fruit bodies of ectomycorrhizal fungi and saprophytic fungi using high-throughput sequencing technology,as well as bacterial diversity in the corresponding hyphosphere soils below the fruit bodies.The results showed that the dominant bacteria,such as Helicobacter,Escherichia-Shigella and Bacillus,habited in the two macro-fungi were similar revealing these common bacteria may be crucial in the development of macro-fungi.The bacterial richness in the hyphosphere of ectomycorrhizal fungi was higher than that of saprophytic fungi and significant differences in the composition of bacterial communities were observed(t=2.48,p<0.05).There were more Verrucomicrobia(t=3.30,p<0.05),Bacteroides(t=2.22,p=0.05),and Nitrospirae(t=2.49,p<0.05)in the hyphosphere of ectomycorrhizal fungi,comparatively more Actinobacteria(t=-5.70,p<0.05)in the hyphosphere of saprophytic fungi.The results indicated that the two types of macro-fungi can enrich,and shape the bacteria compatible with their respective ecological functions.So we explored the interactions between Scleroderma bovista with phosphate-solubilizing bacteria isolated from the mycorrhizosphere of Pinus massoniana.The results showed that there was a significant difference in releasing available phosphorus from the insoluble mineral.The Y5 strain had the best effect of dissolving Ca3(PO4)2(807.32±52.96 mg L-1)and the Y13 strain had highest available phosphorus in all experimental groups by apatite(83.36± 1.70 mg L-1).What's more,the same strains had different dissolution effects of the Ca3(PO4)2 and the apatite.The ecological relationship between the phosphate-solubilizing bacteria and the S.bovista was complicated and the strain Y29,Burkholderia sp.had the best co-culture effect on S.bovista.The extracellular metabolites of Y29 strain,Burkholderia sp.significantly increased the growth of fungal colony diameter and the mycelium mass of the dry weight which may be Mycorrhiza helper bacteria during the process of mycorrhizae.This study will be beneficial for further understanding of the evolutionary rules of microbial community in the process of soil gensis and interactions between macro-fungi and bactertia,which will be provide the theoretical guidance of regulating the process of soil gensis and utilizing resources of macro-fungi and microbial agents.