Rhizosphere Microbial Community Structure And Potential Function Of Two Species Of Seagrass In The Eastern Coast Of Shandong Province

The seagrass bed ecosystem has a rich diversity of microorganisms with active metabolism.They form a symbiotic relationship with seagrass and play an important role in the ecosystem.The characteristics and potential functions of rhizosphere microbial communities of Zostera marina and Phyllospadix iwatensis from the coastal waters of Rongcheng and Penglai were studied using high-throughput amplicon sequencing and metagenomic sequencing technologies Combined with environmental factors,we investigatedthe main factors that drive the structure of seagrass microbial communities were explored.Below are the main results.Alpha diversity analysis shows that the diversity of microbial communities in seagrass rhizosphere sediment samples is higher than that in seawater,and the diversity of bacterial community is higher than that of eukaryotes and fungi.Proteobacteria and Bacteroidetes are the predominant groups of bacteria,while Flavobacteriales are the dominant groups of bacteria in the rhizosphere sediments of Z.marina and P.iwatensis(9.25% and 16.60%),and Rhodobacterales account for a relatively high proportion(39.15%)in seawater.The dominant group of eukaryotes is the phylum Chlorophyta,the order Gymnodiniales is dominant in Z.marina rhizosphere sediments,Ulva is dominant in P.iwatensis rhizosphere sediments,and Cymatosirales is dominant in seawater.Ascomycota is the dominant fungal group of seagrass rhizosphere sediments and seawater,Chytridiomycota dominates the rhizosphere sediments of Z.marina,Rozellomycota dominates the rhizosphere sediments of P.iwatensis,and Basidiomycota constitutes a relatively high proportion(17.04%)of seawater accounts.The microbial community varies with seagrass species and collection sites,and seagrass rhizosphere sediment and seawater in the same site have significant differences.Sulfitobacter,Sulfurovum,Picochlorum,Selenidium,Sarocladium,and Cladosporium are the main groups that differ between sediment and seawater.Sulfurovum,Woeseia,Pheopolykrikos,Selenidium,Clayomyces and Kluyveromyces are the differential groups found in the rhizosphere sediments of Z.marina at different sampling sites.The main different groups in the rhizosphere sediments of P.iwatensis in different regions include Woeseia,Cocleimonas,Monostroma,Endarachne,Metschnikowia,and Saccharomyces.Correlation analysis shows that ammonium,nitrite,nitrate,sulfate,and sediment grain size play an important role in regulating the microbial community structure of the seagrass rhizosphere.In seawater,ammonium and silicatessignificantly influence the structure of microbial communities.For the Z.marina,the rhizosphere microorganisms in Rongcheng Chudao Island have high gene abundance related to reductive citrate cycle,denitrification and assimilatory sulfate reduction,while the gene abundance related to dissimilatory sulfate reduction is low;The abundance of genes related to carbon fixation is low in Penglai Tuoji Island,while the abundance of genes related to denitrification and sulfur oxidation is high;The abundance of functional genes related to carbon fixation pathways such as dicarboxylate-hydroxybutyrate cycle,Calvin cycle,reductive citric acid cycle in Rongcheng Ailian Bay is high,and the abundance of functional genes related to nitrogen fixation is also high;The abundance of functional genes related to carbon metabolism,nitrogen metabolism,and sulfur metabolism in Rongcheng Swan Lake is relatively low.Metagenomic functional analysis showed that microorganisms in the rhizosphere of Z.marina and P.iwatensis were mainly involved in carbon metabolism,nitrogen metabolism and sulfur metabolism.For the Z.marina,the rhizosphere microorganisms in Rongcheng Chudao Island have high gene abundance related to reductive citrate cycle,denitrification and assimilatory sulfate reduction.However,the gene abundance related to dissimilatory sulfate reduction is low.In Penglai Tuoji Island,there is a low abundance of genes related to carbon fixation but a high abundance of genes related to denitrification and sulfur oxidation.Rongcheng Ailian Bay has a high abundance of functional genes related to carbon fixation pathways and nitrogen fixation;Rongcheng Swan Lake has a relatively low number of genes involved in carbon,nitrogen,and sulfur metabolism.For the P.iwatensis,the abundance of functional genes related to sulfur oxidation(soxA,soxB,soxX,soxY,soxZ)in Rongcheng Lidao Island is higher than that in Penglai Changdao Island.Nitrate and nitrite concentrations and sediment grain size are the primary factors influencing the abundance and function of microbial genes involved in carbon fixation,nitrogen metabolism,and sulfur metabolism in seagrass rhizosphere sediments.This study revealed the the structural and potential functions of Zostera marina and Phyllospadix iwatensis microbial communities along the Shandong coast,as well as the environmental factors that influenced the structure of these microbial communities in the rhizosphere of seagrass.The results provide a theoretical basis for the exploitation of seagrass microbial resources for seagrass restoration in the future.