| Marine organisms colonized on surfaces of micro/nano-modified polymeric composites in the marine environment is one of the important issues to be solved in order to maintain their long-term efficiency and stability in service.Although micro/nano-modified polymeric composites were found to have obvious inhibitory effect on the colonization of marine organisms in the seawater environment,marine microorganisms can still colonize on their surfaces and form biofilms,which can subsequently result in the occurrence of marine biofouling.Therefore,it is imperative to clarify the structure characteristics and the actual marine antibiofouling efficiency of the micro/nano-modified polymeric composites,and further reveal the formation of the pioneer biofilms in order to explore the potential mechanisms concerning biofilm formation and the degradation of the micro/nano-modified polymeric composites from the molecular level.In this study,different micro/nano materials were used to modify the marine antifouling performance of chlorinated rubber iron red(CRIR)matrix and polydimethylsiloxane(PDMS)matrix using the actual marine antifouling efficiency as the screening guidance.The surface micro/nanostructure characteristics of CRIR and PDMS before and after material modification were analyzed via various characterization techniques such as SEM,AFM,combined with the asymmetric nano PCR-SSCP technique and the microbiome technique.The actual marine antifouling efficiency,the compositional structures and diversity characteristics,functional characteristics and dynamics of the surface-associated biofilm-forming communities were compared and analyzed.The main results of this study were summarized as follows:1.The doping of small amounts(i.e.0.2 wt %,2.0 wt %)of non-metallic micro/nano materials(i.e.graphite powder,carbon nanotubes)and the combinations of non-metallic micro/nano-materials(i.e.silicon powder/carbon nanopowder,silicon powder/graphite powder,graphite powder/carbon nanopowder)can increase the surface roughness,improve the hydrophobic properties and change the micro/nano-morphological characteristics of CRIR,and thus significantly enhance its actual marine antifouling efficiency.The micro/nano-modified CRIR-based polymeric composites have obvious micro-disturbance effect on the attachment and colonization of pioneer eukaryotic microbes.This microdisturbance effect depended primarily on the types and physicochemical properties of micro/nano materials;2.Obvious differences can be found towards in the antifouling efficacy of different CNTs-modified PDMS composites.This differences mainly depended on the molecular structure characteristics,physicochemical properties of CNTs and the dispersion state of CNTs in the PDMS matrix.The changes in the surface micro-morphology characteristics and the actual marine antifouling efficiency of CNTsmodified PDMS composites may have an important impact on the biofilm formation and the subsequent colonization of major fouling organism such as invertebrate larvae and algae spores;3.The compositional structures of pioneer biofilm communities on the surface of different CNTs modified PDMS composites were found to be generally similar,but the relative abundance was significantly different.The major dominant genera of pioneer biofilm communities were Cycloclasticus,Oleibacter,Alteromonas and Aphelochaeta,Navicula and Pseudovorticella,which were found to be widely involved in the biofilm formation process.There were differences in the diversity and abundance of pioneer biofilm communities on different PDMS-based composites,and the diversity and abundance of pioneer biofilm communities on the cPDMS surface was found to be the lowest.Seawater temperature and immersion time was the main factors can affect the biofilm formation.A total of nine functional modules closely related to the degradation of aromatic hydrocarbons and alkanes as well as the surface colonization of diatoms were excavated via the analysis of correlation network.These functional modules were important for the understanding of the pioneer biofilm formation on different PDMS-based composites;4.The doping amount of cMWCNTs was found to have an important impact on the surface morphology characteristics,the actual marine antifouling effect and the colonization process of pioneer biofilm communities on the surfaces of PDMS.When the doping amount of cMWCNTs was low(0.1～0.5 wt %),cPDMS showed strong antifouling activity,which had significant inhibitory effects on the colonization of pioneer biofilm communities;when the doping content of cMWCNTs was high(>1.0 wt %),cPDMS showed strong adsorption characteristics,which can significantly promote the attachment and colonization of pioneer biofilm communities;5.The pioneer biofilm communities on PDMS and cPDMS surfaces were significantly different from the adjacent seawater.PDMS and cPDMS have obvious selective enrichment effect on the prokaryotic microbes in the adjacent seawater,which exhibited inhibitory effect on the colonization of eukaryotic microbes.There were obvious differences in the dynamics of pioneer biofilm communities on the PDMS and cPDMS surfaces during different sampling periods.DO,SAL and p H of seawater were the main environmental effect factors that affect the formation of pioneer biofilms.There were complex co-occurrence network relationships between prokaryotic and eukaryotic microbes on the PDMS and cPDMS,and the core genera were mainly related to the degradation of aromatic hydrocarbons and alkanes,as well as the surface colonization of Navicula.These aforementioned results showed that cMWCNTs has an obvious micro-regulation effect on the compositional structures,diversity characteristics,functional expression characteristics and dynamics of pioneer biofilm communities.cMWCNTs may achieve the micro-regulatory effect on the attachment and the colonization of marine microbes by changing the species compositions and relative abundance of the dominant bacteria in natural biofilms formation on the surface of PDMS and cPDMS;6.Metagenome sequencing revealed that Oceanobacter sp.,Roseobacter sp.and Massilia sp.,were the main dominant species of PDMS and cPDMS during the initial stages of biofouling.Seawater salinity,p H value and DO were found to be the main environmental effect factors affecting the colonization of dominant species of the pioneer biofilm communities.In addition,it was also found that the diversity of biofilm communities on PDMS and cPDMS was highly consistent both at the function level and the species level.Gene co-occurrence network analysis showed that the transposase genes,metal ion transport genes and metal ion resistance genes showed obvious co-occurrence characteristics,indicating that the transposase genes may be contributable to promoting the transmission of metal ion transport genes and metal ion resistance genes among various marine microbial species in the seawater,thus improving the adsorption and successful colonization of adjacent marine microbial species on the PDMS and cPDMS surfaces.These results showed that gene transfer may be one of the most important mechanisms by which marine microorganisms colonized the surface of different PDMS-based composites and form biofilms.These combined results would not only provide theoretical guidance and experimental basis to further clarify the formation mechanisms of natural biofilms on different micro/nano-modified polymeric composite surfaces in the marine environment,but also provided the potential chemical ecological relationship between micro/nano-modified polymeric composites and biofilm-forming microbes.In addition,these results would provide new clues to clarify the occurrence mechanisms of marine biofouling and corrosion on various micro/nano-modified polymeric composites. |
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