Microbial hitch-hikers of marine plastics: the survival, persistence & ecology of microbial communities in the Plastisphere

海洋环境中最丰富的垃圾形式是塑料，塑料碎片对鱼类、爬行动物、鸟类和哺乳动物的负面和有害影响已有详细记录。水性塑料的坚硬表面为机会性微生物定植者形成生物膜提供了理想的环境;然而，我们对微生物如何与微塑料相互作用并改变海洋塑料在环境中的分散行为的了解是一个重大的研究空白。塑料表面与环境之间界面上的生物膜被称为“塑料圈”，尽管塑料具有极强的抗腐烂能力，但成分的变化决定了其特定的浮力和表面粗糙度，这将决定微生物的定植程度及其远距离传播的能力。此外，由于塑料碎片在海洋环境中的存留时间比羽毛和木材等天然基质长，因此为致病和有害微生物的更广泛传播提供了机会。来自衣服、化妆品和卫生用品的微塑料现在是污水系统的常见组成部分，它们经常绕过旨在清除较大废物的筛选机制，以免出口到沿海沃茨。从废水处理厂（WWTP）进入水生系统的微塑料与人类粪便密切接触，因此为粪便指示生物（FIO）和一系列人类细菌病原体的定殖提供了重要机会。然而，重要的是，从来没有任何研究调查肠道病毒与微塑料结合（或与塑料表面上的生物膜结合）的能力，现在需要进行严格的评估，以了解肠道病毒环境传播的这种潜在的新机制。此外，越来越多的证据表明，塑料球可以促进基因交换，因此确定塑料球生物膜为抗微生物抗性（AMR）基因转移提供表面的潜力至关重要。目前对微生物，特别是致病细菌和病毒可以在微塑料颗粒上“搭便车”并被运送到海滩、洗澡沃茨、贝类收获沃茨和高底栖生物多样性区的机制缺乏基本了解。因此，目前尚无法确定这些潜在途径的风险，也无法制定环境监测准则，为未来的政策或环境法规提供信息。因此，该项目的新奇在于量化塑料球内发生的过程，并了解致病病毒和细菌的潜在载体。以前对塑料上存在的化学共污染物的研究往往没有考虑塑料圈群落的可能影响。环境中的微塑料是这些化学品的潜在载体，这些化学品在被海洋物种摄入时往往会解吸，并可能在食物链中积累。塑料球中的微生物可以通过生物降解来缓解这一问题，或者通过增加生物膜结合来增强这一问题;然而，大多数基于实验室的研究都是使用原始的非殖民化塑料进行的，忽略了塑料球在定义环境中微塑料风险方面的关键作用。通过了解微塑料的多污染物和多尺度效应，“塑料载体项目”将有助于通过考虑有害塑料相关微生物以及化学共污染物的影响，建立更准确的微塑料风险评估。因此，“塑料载体项目”旨在量化“塑料圈”中微生物的重要性和功能，并为降低这些多污染物风险提供可行的解决方案。

The most abundant form of litter in the marine environment is plastic, and the negative and detrimental consequences of plastic debris on fish, reptiles, birds and mammals are well documented. The hard surface of waterborne plastic provides an ideal environment for the formation of biofilm for opportunistic microbial colonisers; however, our knowledge of how microorganisms interact with microplastics and alter the dispersal behaviour of marine plastics in the environment is a significant research gap. Biofilm at the interface between the plastic surface and the environment has been termed the 'Plastisphere', and although plastics are extremely resistant to decay, variability in composition determines their specific buoyancy and surface rugosity, which will dictate the extent of microbial colonisation and their ability for long distance dispersal. Furthermore, because plastic debris can persist in the marine environment longer than natural substrates, e.g. feathers and wood, it offers an opportunity for the wider dissemination of pathogenic and harmful microorganisms. Microplastics from clothes, cosmetics and sanitary products are now common constituents of sewage systems and they frequently bypass the screening mechanisms designed to remove larger waste items from being exported to coastal waters. Microplastics entering aquatic systems from waste water treatment plants (WWTPs) come in close contact with human faeces, hence providing significant opportunity for colonisation by faecal indicator organisms (FIOs) and a range of human bacterial pathogens. Importantly however, there have never been any studies investigating the ability of enteric viruses binding to microplastics (or binding to the biofilm on the plastic surface), and this now needs critical evaluation in order to understand this potentially novel mechanism for the environmental dispersal of enteric viruses. Furthermore, there is growing evidence that the plastisphere can promote gene exchange, and so determining the potential of plastisphere biofilms for providing the surface for anti-microbial resistance (AMR) gene transfer is of the utmost importance. There is currently a lack of fundamental understanding about the mechanisms by which microorganisms, particularly pathogenic bacteria and viruses, can "hitchhike" on microplastic particles and be transported to beaches, bathing waters, shellfish harvesting waters and high benthic diversity zones. Consequently, it is not yet possible to determine the risk from these potential pathways, or establish environmental monitoring guidelines for informing future policy or environmental regulation. Therefore, the novelty of this project is to quantify the processes that are occurring within the plastisphere, and understand the potential for the vectoring of pathogenic viruses and bacteria. Previous research on chemical co-pollutants present on plastics often fails to consider the likely impacts of plastisphere communities. Microplastics in the environment are potential vectors for these chemicals, which often desorb when ingested by marine species, and can accumulate in the food chain. Microbes in the plastisphere may either mitigate this problem through biodegradation, or enhance it by increased biofilm binding; however, most laboratory-based studies are carried out with pristine non-colonised plastics, and ignore the pivotal role the plastisphere plays on defining the risk of microplastics in the environment. By understanding the multi-pollutant and multi-scale effects of microplastics, the "Plastic Vectors Project" will help to establish a more accurate risk assessment of microplastics by taking into consideration the effects of harmful plastic-associated microbes together with chemical co-pollutants. Therefore, the "Plastic Vectors Project" aims to quantify the significance and function of microbes in the 'plastisphere', and will deliver feasible solutions for reducing these multi-pollutant risks.