| Plastic mulching film is one of the materials commonly used in agricultural production in my country.While it brings huge benefits to the agricultural economy,it also causes serious pollution to the environment.In order to solve the problem of "Plastics Pollution" in farmland,black and white plastic mulching films commonly used in agriculture were taken as the research object in the study.Soil samples were collected from two long-term mulching farmlands in Xinjiang and Yangling.Combined with enrichment culture method,the effects of plastic mulching film pollutants on the community structure of uncultured and culturable microorganisms were analyzed by using 16 S r DNA high-throughput sequencing and traditional microorganisms separation culture technology.The potential plastic degrading bacteria were screened from some mixed bacterial consortium that were constructed artificially.Furthermore,the degradation of plastic films by potential plastic degrading bacteria/ bacterial consortium were evaluated throwing the growth bacterial,membrane weightlessness rate,the changes in the film surface microscopic morphology and chemical functional groups.The high-efficiency degrading bacteria community of plastic mulch was screened out.The study provides a theoretical basis for comprehensive degradation of residual mulching film and remediation of environmental pollution.The results of this study are as follows:(1)The microbial community composition between the initial soil and the post-enrichment treatment group is significantly different,and the soil source has little effect on the microbial community structure.The specific performance is that the treatment group has more Proteobacteria and a variety of bacteria that can degrade plastics,alkanes,and plasticizers than the initial soil.Compared with the types of plastic mulch film,the soil source is more important than the original soil.The cultivable microbial community has no significant impact,which is manifested as the significant difference in microbial community structure between the treatment groups from the same soil source and no common dominant bacteria genus.(2)The color of plastic mulch pollutants has a greater impact on the community composition of microorganisms.There are significant differences in the microbial communities of the plastic film treatment groups with different colors and no common dominant microorganisms,while the same color plastic film treatment groups can be enriched with the same dominant microorganisms,suggesting that these dominant microorganisms may be potential plastic degrading bacteria.For example,Paenarthrobacter and Rhodanobacter were significantly enriched in white film treatment group,and Acinetobacter,Chryseobacterium,and Sphingopyxis were significantly enriched in black film treatment group.Through the traditional microbial isolation and culture system,combined with the related literature of plastic degrading bacteria,seven potential plastic degrading bacteria were initially screened,namely Rhodanobacter lindaniclasticus(RL),Rhodanobacter soli(RS),Bacillus LGUF-s(BL),Sphingopyxis gisengisoli(SG),Sphingopyxis flava(SF),Paenarthrobacter nitroguajacolicus(PN),Paenarthrobacter aurescens(PA).(3)The unculturable/culturable microbial community had a certain succession rule with the cultivation time,which showed that the community composition difference between the initial soil and the treatment group occurred gradually,and there was no significant difference in the microbial community structure between the first two stages and the initial soil,but the difference appeared in the third stage;The microbial community composition in the same treatment group gradually stabilized with the cultivation time,that is,the microbial community structure in the early stage(stage 1,2,3)was quite different.In the later stages(stages 4,5,and 6),the microbial community gradually stabilized,the community composition was similar,the dominant bacteria were the same,and the microbial community tended to be homogenized.(4)Seven potential plastic-degrading bacteria were used as the test strains,and the mixed bacterial consortium were artificially constructed.A total of 30 treatment groups were screened for efficient plastic-degrading bacteria(consortium).The results showed that after120 days of degradation in SG-SF-BL(Sphingopyxis gisengisoli-Sphingopyxis flava-Bacillus LGUF-s)and RS-PN-PA(Rhodanobacter soli-Paenarthrobacter nitroguajacolicus-Paenarthrobacter aurescens)treatment groups,a large number of microorganisms were enriched on the surface of plastic film and obvious grooves and pits were formed.FTIR showed that a large number of oxygen-containing functional groups were introduced into the chemical structure of polyethylene,and the weight loss rate of plastic film was as high as 11% and 10.67%,respectively,which was the best treatment group for degradation effect.In conclusion,the community structure of soil microbial community was significantly different between the initial soil and the treatment group after the enrichment culture of plastic mulch.Different soil sources had little influence on the uncultured/culturable microbial community,while plastic mulch had more significant influence on the uncultured/culturable microbial community.In addition,the uncultured /culturable microbial community showed a certain succession rule with the increase of culture time.The selected potential plastic degrading bacteria were artificially constructed to carry out the plastic mulching film degradation test,and the final SG-SF-BL and RS-PN-PA treatment groups screened had high degradation efficiency,which was highly degrading bacteria.The results provided a potential strain resource and reference value for solving the environmental pollution caused by waste plastic mulching film. |
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