The Contributions Of Marinilabiliales In Microbial Community Succession During Sediment Enrichment Cultures Process

Since the establishment of the order Marinilabiliales in 2016,it currently includes four higher taxonomic units:the family Marinilabiliaceae,Prolixibacteraceae,Marinifilaceae,and Salinivirgaceae.During the enrichment cultivation process of marine sediments,the relative abundance and activity of Marinilabiliales have been observed to increase.However,there is currently limited research on the contribution of Marinilabiliales to microbial community succession during the enrichment cultivation process in marine sediments.Therefore,this study aims to investigate the contribution of Marinilabiliales to community assembly and molecular ecological networks during the succession of simplified microbial communities.To achieve this,the study integrates the research progress of Marinilabiliales,simplified microbial community techniques,and microbial macroecology.By conducting highly replicable microcosm experiments of marine sediment enrichment cultivation,two different approaches were used to obtain simplified microbial communities.These approaches were employed to explore the role of Marinilabiliales in community assembly and molecular ecological networks during the succession of simplified microbial communities.To investigate the contribution of Marinilabiliales in the succession of the progressively simplified microbial community,this study employed gradient dilution to simulate random species loss events,resulting in microbial communities of varying degrees of simplification.Using a highly replicable microcosm experiment system in marine sediment enrichment cultures,the results revealed that the differences in beta diversity of the progressively simplified microbial communities were primarily influenced by a combination of species loss and species turnover,with species loss being the major factor.By quantifying the relative importance of different mechanisms during microbial community assembly,this study found a positive linear relationship between ecological drift and dilution intensity.This implies that higher dilution intensity leads to an increased relative importance of ecological drift in the microbial community assembly process.Furthermore,gradient dilution reduced the stability of microbial community networks,increased the vulnerability of networks,and amplified the negative frequency correlations among network nodes(species).Regarding the contribution of Marinilabiliales in the succession of the progressively simplified microbial community,three main aspects were identified.Firstly,Marinilabiliales made a substantial contribution to the homogenizing selection mechanism during microbial community assembly in higher dilution treatments.Secondly,they played an important role in the composition of network modules and key nodes within the gradient dilution process,as well as contributing to the composition of preserved modules in the molecular ecological network under higher dilution treatments.Lastly,Marinilabiliales exhibited a "generalist" attribute or an ecological "jack-of-all-trades"characteristic in microbial community succession across different gradient dilution treatments.To investigate the role of Marinilabiliales,known as "ecological jack-of-all-trades," in the microbial molecular ecological network,this study conducted microbial pure culture experiments to identify key taxa within network modules.A total of 3,141 bacterial strains were isolated and classified.These strains were mainly distributed among four common phylum taxon:Actinomycetota(84),Bacillota(199),Bacteroidota(761),and Pseudomonadota(2,097).Furthermore,we identified a total of 388 novel strains(16S rRNA similarity ≤98.65%)from the isolates obtained in different dilution groups,and these novel strains were primarily classified into the following four common phylum taxon:Actinomycetota(24),Bacillota(65),Bacteroidota(37),and Pseudomonadota(262).Based on the isolated strains,12 representative strains were selected for co-cultivation experiments involving 11 synthetic microbial communities to explore the coexistence relationship between Marinilabiliales and theirassociated taxa within network modules of the molecular ecological network.The results demonstrated that Marinilabiliales played a role in promoting positive interactions among multiple species.To further investigate the contribution of Marinilabiliales in the succession of the simplified microbial community,this study simulated the removal of specific functional groups by adding a sulfate-reducing bacteria inhibitor(molybdate).This process aimed to mimic environmental disturbances and obtain simplified microbial communities.The experimental approach involved a highly replicable microcosm system in marine sediment enrichment cultures.Half of the cultures were treated without molybdate,while the other half had molybdate added to inhibit sulfate-reducing bacteria within the microbial community.In total,180 related 16S rRNA gene high-throughput sequencing datasets were obtained.When the sulfate-reducing bacteria were inhibited within the microbial community,the stability of the molecular ecological network decreased,and its vulnerability increased.The associations between network nodes became "loose," and the relative importance of stochastic assembly processes in microbial community assembly increased.Based on various quantifiable measures of microbial communities,it was found that Marinilabiliales and sulfate-reducing bacteria were closely associated taxa in the enrichment culture process of marine sediments.Furthermore,the relative abundance of both groups was simultaneously affected by molybdate.The contribution of Marinilatiliales and sulfate-reducing bacteria to microbial community succession was evident in two aspects:(1)they served as key nodes in the molecular ecological network and important components of preserved modules,mitigating the decay of network stability in closed systems and maintaining the succession of preserved network modules;(2)they made significant contributions to the homogenous selection in microbial community assembly.To further explore the potential coexistence mechanisms between sulfate-reducing bacteria and Marinilabiliales,the study analyzed 27 related 16S rRNA gene high-throughput sequencing datasets.By comparing the relative abundance changes of Marinilabiliales and sulfate-reducing bacteria,as well as pH variations,in three different enrichment culture processes of marine sediments("without molybdate," "with molybdate," and "with molybdate+pH buffer"),it was suggested that sulfate-reducing bacteria might promote coexistence with Marinilabiliales and other taxa by modulating the pH in the microenvironment(niche modification).This study employed two different types of simplified microbial,and aimed to investigate the contribution of Marinilabiliales in microbial community assembly and molecular ecological networks during marine sediment enrichment culture.The findings have deepened our understanding of the role of Marinilabiliales in microbial community succession.Moreover,the study explored the potential mechanisms of coexistence between Marinilabiliales and their closely associated taxa,providing a valuable research framework for further investigations into the involvement of other important taxa in microbial community succession.