Molecular Ecological Investigation Of Pioneer Biofouling-related Biofilm Communities Colonized On The Polydimethylsiloxane Surface

Marine biofouling has caused huge economic losses to marine fishery industry and marine transportation industry in China,which has seriously hindered the development of marine economy in China.Marine antifouling coating is one of the most effective methods to prevent and combat marine biofouling-related problems.Traditional marine antifouling coatings can not only prevent biofouling,but also cause severe damage to the marine ecological environment.Therefore,the development of environment-friendly marine antifouling materials has become the hotspot which has won worldwide attention.Polydimethylsiloxane（PDMS）is a kind of organic silicon matrix material with excellent properties,such as low surface energy,high hydrophobicity and high elastic modulus etc..However,during its actual marine application,its perfect performance would be further weakened due to surface biofouling.In previous studies,we found that the formation of biofilms on PDMS surface is one of the important causes of surface biofouling.However,so far,the structural characteristics and diversity characteristics of the biofilm communities on PDMS surface and the formation mechanisms of biofilms still remain unclear.In view of this,we used the second-generation high-throughput sequencing technology to analyze the compositions,diversity characteristics,distribution characteristics and dynamics rules of the biofilm communities on the PDMS surface,in order to reveal the formation mechanisms of biofilm communities on the PDMS surface at the molecular level,and to clarify the molecular mechanisms of the occurrence of surface biofouling of PDMS.Briefly,a21-day continuous biofilm sample of pioneer biofilm samples on PDMS surface was performed via a short-term marine field experiment and metagenomics was extracted.Then the 16S r DNA,18S r DNA and ITS genes were used as biomarkers to amplify 16S r DNA（V3+V4）region,18S r DNA V4 region and ITS-1 region gene fragments from the biofilms to screen the pioneer prokaryotes,eukaryotes and marine fungi,respectively.Based on the Illumina sequencing platform,the high throughput sequencing was performed and the bioinformatics analysis of the sequencing data was conducted in order to explore the dominant prokaryotes,eukaryotes and marine fungi in biofilm samples at each taxonomy level.The specific research results of this study were presented as follows:（1）By bioinformatics analysis of the high throughput sequencing data of prokaryotes,eukaryotes and fungi on the PDMS surface,we found that the main dominant phyla of the prokaryotes in biofilms formed on the PDMS surface were:Proteobacteria,Bacteroidetes,Epsilon Bacteraeota,Firmicutes.Chrysophyceae,Phaeophyceae,Chordata and Streptophyta were the dominant phyla in eukaryotes in biofilms formed on the PDMS surface.The dominant phyla of marine fungi in biofilms formed on the PDMS surface were Ascomycota,Basidiomycota.（2）The complexity analysis and multi-sample comparative analysis showed that there were significant differences in the structure of prokaryotes in biofilm samples taken at different immersion weeks,but with the increase of immersion time,the structural similarity of prokaryotes gradually enhanced and tended to evolve similar.The eukaryotes on the PDMS surface biofilm collected at different immersion weeks had experienced a continuous dynamic succession process,but the succession rate gradually slowed down.（3）The correlation analysis of environmental factors showed that immersion time and phosphate concentration had the greatest correlation with the distribution of prokaryotes and eukaryotes.The immersion time of hanging plate and NO₂concentration in seawater had the greatest correlation with the distribution of marine fungi.（4）By analyzing the relative abundance of the dominant bacteria,the relationship between the dominant bacteria and the prokaryotic bacteria,eukaryotic bacteria and marine fungi were explored.It was found that the top three bacteria in the highest content group of the various microbial communities fluctuated,and their diversity parameters were in constant fluctuations.After two weeks of immersion,the variatiosn range and trend of dominant bacteria gradually tended to be similar,which might be caused by the shedding and renewal of biofilm.The above research results are of great significance for the understanding the formation mechanisms of biofilms on PDMS surface,revealing the molecular mechanisms of the surface biofouling of PDMS resin,and clarifying the molecular mechanisms of interactions between PDMS and marine microorganisms.