Invertebrate effects on sediment biogeochemistry and microphytobenthos following estuarine macroalgal blooms

Eutrophication has led to the proliferation of devastating macroalgal blooms in shallow coastal estuaries. Processes at the sediment surface in shallow marine environments can ultimately affect nutrient cycling and the progress of eutrophication. Through bioturbation and grazing of microphytobenthos (MPB) infaunal invertebrates significantly alter redox dependent chemical and microbially-mediated transformations of nutrients and their subsequent release to or uptake from the overlying water column. This study used a series of experiments to investigate the effects of invertebrates on sediment biogeochemistry and nutrient cycling at early and late stages of eutrophication. Unique aspects of this study were the inclusions of multiple species, trophic levels and the use of technology to better understand the effects of invertebrates on processes. A non-destructive method of remotely sensing the MPB community through the use of reflectance spectra of the sediment surface was developed. Indices, derivatives and continuum removal band depths were valid for non-destructively quantifying MPB biomass at different time points in an ecological microcosm experiment. In another experiment, we evaluated the effects of two species of invertebrates, Ilyanassa obsoleta and Mercenaria mercenaria, alone and in combination, on the removal of detritus, oxygen consumption and nutrient release following the collapse of a large algal bloom. The effect I. obsoleta had on detritus removal was context specific, due to changes in food preferences in different sediment types. M. mercenaria’s effect on sediment oxygen concentrations was substantially lower in the presence of I. obsoleta suggesting the importance of inter-specific interactions. In a third experiment we found that non-lethal predation by mud-crabs substantially affects invertebrates‟ behavior by reducing their activity. I. obsoleta grazed less, resulting in greater MPB biomass and decreased sediment ammonium release. Likewise, higher porewater ammonium concentrations when M. mercenaria was in the presence of a predator indicate lower bioturbation within the sediments. Based on these studies, we conclude that environmental conditions and assemblage diversity ultimately affect the behavior of the organisms, which has potentially important consequences on the progress of eutrophication

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Startle to neutral, not negative stimuli: A neurophysiological correlate of behavioral inhibition in young children

A putative biomarker of anxiety risk, the startle response is typically enhanced by negative compared to neutral emotion modulation in adults, but remains understudied in children. To determine the extent to which neutral, negative, and positively valenced emotional conditions modulate startle response in early life, a child‐friendly film paradigm was used to vary emotion across these conditions during startle induction in sixty‐four 4‐ to 7‐year‐old children. Association of emotion‐modulated startle with parent‐reported anxiety symptom severity and child behavioral inhibition, a risk factor for anxiety problems, were assessed. Analyses revealed no difference in startle magnitude during negative compared to neutral film clips. By contrast, startle during both negative and neutral conditions was greater than startle during the positive condition. Larger startle magnitude during the neutral condition associated with higher levels of child behavioral inhibition (BI). These results are consistent with possible immaturity of startle response in young children, and suggest that startle amplitude in more emotionally ambiguous, neutral conditions could serve as an early biomarker for anxiety risk.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/169324/1/dev22120_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/169324/2/dev22120.pd

Extrafollicular IgD−CD27−CXCR5−CD11c− DN3 B cells infiltrate inflamed tissues in autoimmune fibrosis and in severe COVID-19

Summary: Although therapeutic B cell depletion dramatically resolves inflammation in many diseases in which antibodies appear not to play a central role, distinct extrafollicular pathogenic B cell subsets that accumulate in disease lesions have hitherto not been identified. The circulating immunoglobulin D (IgD)−CD27−CXCR5−CD11c+ DN2 B cell subset has been previously studied in some autoimmune diseases. A distinct IgD−CD27−CXCR5−CD11c− DN3 B cell subset accumulates in the blood both in IgG4-related disease, an autoimmune disease in which inflammation and fibrosis can be reversed by B cell depletion, and in severe COVID-19. These DN3 B cells prominently accumulate in the end organs of IgG4-related disease and in lung lesions in COVID-19, and double-negative B cells prominently cluster with CD4+ T cells in these lesions. Extrafollicular DN3 B cells may participate in tissue inflammation and fibrosis in autoimmune fibrotic diseases, as well as in COVID-19