Weaver, T. | bioRxiv Science

bioRxiv2023

Polybacterial intracellular coinfection of epithelial stem cells in periodontitis

Periodontitis affects billions of people worldwide. To address interkingdom relationships of microbes and niche on periodontitis, we generated the first sin-gle-cell meta-atlas of human periodontium (34-sample, 105918-cell), harmo-nizing 32 annotations across 4 studies1-4. Highly multiplexed immunofluores-cence (32-antibody; 113910-cell) revealed spatial innate and adaptive immune foci segregation around tooth-adjacent epithelial cells. Sulcular and junctional keratinocytes (SK/JKs) within epithelia skewed toward proinflammatory phe-notypes; diseased JK stem/progenitors displayed altered differentiation states and chemotactic cytokines for innate immune cells. Single-cell metagenomics utilizing unmapped reads revealed 37 bacterial species. 16S and rRNA probes detected polybacterial intracellular pathogenesis ("co-infection") of 4 species within single cells for the first time in vivo. Challenging coinfected primary human SK/JKs with lipopolysaccharide revealed solitary and synergistic ef-fects. Coinfected single-cell analysis independently displayed proinflammatory phenotypes in situ. Here, we demonstrate the first evidence of polybacterial intracellular pathogenesis in human tissues and cells--potentially influencing chronic diseases at distant sites.

cell biology↗

bioRxiv2022

Ecosystem gross primary productivity after autumn snowfall and melt events in a mountain meadow

Vegetation productivity is increasing across much of the U.S. Northern Great Plains but is decreasing in some nearby Northern Rocky Mountain grasslands due to increases in aridity. Mountain grasslands support critical ecosystem services that are under threat from ongoing land use and climate changes, and it is important to understand their function across all changing seasons. Observing the full range of montane ecosystem productivity is challenging because site access is often difficult during the "shoulder seasons" in spring and autumn if the snowpack is not fully developed or degrading. It is unclear if decreases to montane grassland productivity from drying autumns can be offset in part by late-season green-ups after precipitation events. These include the snowfall/snowmelt periods that often characterize the summer-to-winter transition in the Northern Rockies. Here, we quantify the ecosystem carbon uptake that occurs after snowfall and melt in climatological autumn (September, October, and November) in a montane grassland in Montana, USA using a combination of eddy covariance, phenological camera, and remote sensing analyses. Carbon dioxide flux follows a diurnal pattern after autumn snowmelt events despite overall ecosystem losses of C, suggesting that post-snowmelt photosynthesis helps dampen C loss during autumn and provides fresh photosynthate to support ecosystem functioning. Light-saturated photosynthesis after two snow events was not different than before snowfall ([~]6 {micro}mol CO2 m-2 s-1 in 2016 and [~]2.5 {micro}mol CO2 m-2 s-1 in 2017); observations are consistent with the notion that canopy photosynthesis is resistant, rather than resilient, to the first snow disturbances. MODIS observations also suggest that post-snowfall increases in NDVI can occur but do not happen every year, such that late-season photosynthesis is not a reliable source of fresh photosynthate. These late-season carbon uptake events likely play a small role in the annual ecosystem carbon balance but may be disproportionately important for organisms faced with dwindling late-season forage and regrowth in spring. Future efforts should seek to understand the community and ecosystem consequences of vegetation functioning during autumn as part of an expanded effort to understand phenological changes during this under-studied and changing time of year.

ecology↗