INTRODUCTION: More and more researchers are studying the effects of microplastics on the environment and the organisms living in it. Existing detection methods still require a heavy workload, complex sample preparation and high costs. In this study, autofluorescence of plastic was used as a new method for microplastic detection. MATERIAL AND METHODS: Particles of common plastics were incubated at various temperatures (21–230 °C) for different time periods to investigate the influence of these conditions on their autofluorescence using methods like fluorescence microscopy, and measurement of absorption and emission. To give an example of an autofluorescence application, ImageJ was used to determine the contamination of microplastic in sea salt samples. RESULTS: After treatment at 140 °C for 12 h the plastics ABS, PVC and PA showed a distinct increase in their fluorescence intensity. For PET higher temperatures were necessary to achieve higher fluorescence intensities. Using ImageJ, the particle contamination in sea salt samples was determined as 4903±2522 (aluminium membrane) / 5053±2167 (silicone membrane) particles in 10 g salt, which is a much higher number than counted in other publications. DISCUSSION: Probably the increase in fluorescence intensity is due to the movement of atomic bonds caused by the thermic energy during the heat treatment. The high number of counted particles by using ImageJ is most likely based on the smaller pore size of the used filter membranes and other contaminations like dust and fibers, which could be avoided by alternative sample treatment. CONCLUSION: Considering the outcomes of this study, heat treatment is a useful tool to make microplastic particles more visible in microscopic applications without readable destruction of their composition. The heat treatment of plastics for defined incubation times and temperatures can lead to a distinct increase in autofluorescence intensity of the plastics and therefore serve as an easy and cost-effective applicable method for microplastic detection.
Kitchen sponges are particularly well known to harbor a high number and diversity of bacteria, including pathogens. Viruses, archaea, and eukaryotes in kitchen sponges, however, have not been examined in detail so far. To increase knowledge on the non-bacterial kitchen sponge microbiota and its potential hygienic relevance, we investigated five used kitchen sponges by means of metagenomic shot-gun sequencing. Viral particles were sought to be enriched by a filter step during DNA extraction from the sponges. Data analysis revealed that ~ 2% of the sequences could be assigned to non-bacterial taxa. Each sponge harbored different virus (phage) species, while the present archaea were predominantly affiliated with halophilic taxa. Among the eukaryotic taxa, besides harmless algae, or amoebas, mainly DNA from food-left-overs was found. The presented work offers new insights into the complex microbiota of used kitchen sponges and contributes to a better understanding of their hygienic relevance.
In Parkinson’s disease (PD), α-synuclein is a key protein in the process of neurodegeneration. Besides motor symptoms, most PD patients additionally suffer from gastrointestinal tract (GIT) dysfunctions, even several years before the onset of motor disabilities. Studies have reported a dysbiosis of gut bacteria in PD patients compared to healthy controls and have suggested that the enteric nervous system (ENS) can be involved in the development of the disease. As α-synuclein was found to be secreted by neurons of the ENS, we used RNA-based stable isotope probing (RNA-SIP) to identify gut bacteria that might be able to assimilate this protein. The gut contents of 24 mice were pooled and incubated with isotopically labelled (13C) and unlabelled (12C) α-synuclein. After incubation for 0, 4 and 24 h, RNA was extracted from the incubations and separated by density gradient centrifugation. However, RNA quantification of density-resolved fractions revealed no incorporation of the 13C isotope into the extracted RNA, suggesting that α-synuclein was not assimilated by the murine gut bacteria. Potential reasons and consequences for follow-up-studies are discussed.
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