Phylogenetic diversity of core rumen microbiota as described by cryo-ET

Microbial taxonomy is critical for describing ecosystem composition, yet the link between taxonomy and properties of microbes, such as their cellular architecture, remains poorly defined. We hypothesized that the cellular architecture represents microbial niche adaptation. We used cryo-electron microscopy and tomography to analyze microbial morphology in order to associate cellular architecture with phylogeny and genomic contents. As a model system, we chose the core rumen microbiome and imaged a large isolate collection covering 90% of its richness at the order level. Based on quantifications of several morphological features, we found that the visual similarity of microbiota is significantly related to their phylogenetic distance. Up to the Family level, closely related microbes have similar cellular architectures, which are highly correlated with genome similarity. However, in more distantly related bacteria, the correlation both with taxonomy and genome similarity is lost. This is the first comprehensive study of microbial cellular architecture and our results highlight that structure remains an important parameter in classification of microorganisms, along with functional parameters such as metabolomics. Furthermore, the high-quality images presented in this study represent a reference database for the identification of bacteria in anaerobic ecosystems.

From properties to toxicity: Comparing microplastics to other airborne microparticles

Microplastic (MP) debris is considered as a potentially hazardous material. It is omnipresent in our environment, and evidence that MP is also abundant in the atmosphere is increasing. Consequently, the inhalation of these particles is a significant exposure route to humans. Concerns about potential effects of airborne MP on human health are rising. However, currently, there are not enough studies on the putative toxicity of airborne MP to adequately assess its impact on human health. Therefore, we examined potential drivers of airborne MP toxicity. Physicochemical properties like size, shape, ζ-potential, adsorbed molecules and pathogens, and the MP's bio-persistence have been proposed as possible drivers of MP toxicity. Since their role in MP toxicity is largely unknown, we reviewed the literature on toxicologically well-studied non-plastic airborne microparticles (asbestos, silica, soot, wood, cotton, hay). We aimed to link the observed health effects and toxicology of these microparticles to the abovementioned properties. By comparing this information with studies on the effects of airborne MP, we analyzed possible mechanisms of airborne MP toxicity. Thus, we provide a basis for a mechanistic understanding of airborne MP toxicity. This may enable the assessment of risks associated with airborne MP pollution, facilitating effective policymaking and product design.