Alterations of oral microbiota and impact on the gut microbiome in type 1 diabetes mellitus revealed by integrated multi-omic analyses.

BACKGROUND: Alterations to the gut microbiome have been linked to multiple chronic diseases. However, the drivers of such changes remain largely unknown. The oral cavity acts as a major route of exposure to exogenous factors including pathogens, and processes therein may affect the communities in the subsequent compartments of the gastrointestinal tract. Here, we perform strain-resolved, integrated meta-genomic, transcriptomic, and proteomic analyses of paired saliva and stool samples collected from 35 individuals from eight families with multiple cases of type 1 diabetes mellitus (T1DM). RESULTS: We identified distinct oral microbiota mostly reflecting competition between streptococcal species. More specifically, we found a decreased abundance of the commensal Streptococcus salivarius in the oral cavity of T1DM individuals, which is linked to its apparent competition with the pathobiont Streptococcus mutans. The decrease in S. salivarius in the oral cavity was also associated with its decrease in the gut as well as higher abundances in facultative anaerobes including Enterobacteria. In addition, we found evidence of gut inflammation in T1DM as reflected in the expression profiles of the Enterobacteria as well as in the human gut proteome. Finally, we were able to follow transmitted strain-variants from the oral cavity to the gut at the individual omic levels, highlighting not only the transfer, but also the activity of the transmitted taxa along the gastrointestinal tract. CONCLUSIONS: Alterations of the oral microbiome in the context of T1DM impact the microbial communities in the lower gut, in particular through the reduction of "mouth-to-gut" transfer of Streptococcus salivarius. Our results indicate that the observed oral-cavity-driven gut microbiome changes may contribute towards the inflammatory processes involved in T1DM. Through the integration of multi-omic analyses, we resolve strain-variant "mouth-to-gut" transfer in a disease context. Video Abstract.

Metamorphosis enhances the effects of metal exposure on the mayfly, Centroptilum triangulifer.

The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to explain this pattern is that insects exposed to elevated metal in their larval stages have a reduced ability to successfully complete metamorphosis. To test this hypothesis we exposed late-instar larvae of the mayfly, Centroptilum triangulifer, to an aqueous Zn gradient (32-476 µg/L) in the laboratory. After 6 days of exposure, when metamorphosis began, larval survival was unaffected by zinc. However, Zn reduced wingpad development at concentrations above 139 µg/L. In contrast, emergence of subimagos and imagos tended to decline with any increase in Zn. At Zn concentrations below 105 µg/L (hardness-adjusted aquatic life criterion), survival between the wingpad and subimago stages declined 5-fold across the Zn gradient. These results support the hypothesis that metamorphosis may be a survival bottleneck, particularly in contaminated streams. Thus, death during metamorphosis may be a key mechanism explaining how stream metal contamination can impact terrestrial communities by reducing aquatic insect emergence.

Impaired Acroneuria sp. (Plecoptera, Perlidae) populations associated with aluminum contamination in neutral pH surface waters.

Our aim was to quantify impairment to invertebrate predator populations, particularly to Acroneuria sp. (Plecoptera, Perlidae), downstream of an acid mine drainage-impacted tributary to the North Fork of the Powell River, southwestern Virginia. Predatory insects comprised 9.0 +/- 1.3% of the total abundance at the three stations upstream of the impacted tributary, but were significantly reduced (p = 0.0039) downstream (3.9 +/- 0.6%). Acroneuria sp. populations followed the same trend, with the upstream average (2.3 and 2.8%) being significantly higher (p < 0.05) than the downstream averages (0.2 and 0%) during 1999 and 2000, respectively. Using correlation analysis, we evaluated the relationship between the percent abundance of Acroneuria sp. throughout this reach and metal concentrations in water, sediment, and biological tissues (invertebrate predators and primary consumers). Water column aluminum (Al) concentration was the only parameter that was significantly correlated with percent Acroneuria sp. abundance, with correlation coefficients of -0.845 and -0.873 during 1999 and 2000, respectively. While this correlation exists, it may not indicate a causal relationship, and experiments should be conducted to determine the long-term toxicity of various Al species to perlid stoneflies.