Biology Commons^™

Evidence That A Respiratory Shield In Escherichia Coli Protects A Low-Molecular-Mass Fe-Ii Pool From O2-Dependent Oxidation, Joshua D. Wofford, Naimah Bolaji, Nathaniel Dziuba, Franklin Wayne Outten, Paul A. Lindahl

Faculty Publications

Iron is critical for virtually all organisms, yet major questions remain regarding the systems' level understanding of iron in whole cells. Here, we obtained Mössbauer and EPR spectra of Escherichia coli cells prepared under different nutrient iron concentrations, carbon sources, growth phases, and O₂ concentrations to better understand their global iron content. We investigated wild-type cells and those lacking Fur, FtnA, Bfr, and Dps proteins. The coarse-grain iron content of exponentially growing cells consisted of iron-sulfur clusters, variable amounts of nonheme high-spin Fe^II species, and an unassigned residual quadrupole doublet. The iron in stationary-phase cells was dominated by …

Evolving Paradigms In Biological Carbon Cycling In The Ocean, Chuanlun Zhang, Hongyue Dang, Farooq Azam, Ronald Benner, Louis Legendre, Uta Passow, Luca Polimene, Carol Robinson, Curtis A. Suttle, Nianzhi Jiao

Faculty Publications

Carbon is a keystone element in global biogeochemical cycles. It plays a fundamental role in biotic and abiotic processes in the ocean, which intertwine to mediate the chemistry and redox status of carbon in the ocean and the atmosphere. The interactions between abiotic and biogenic carbon (e.g. CO₂, CaCO₃, organic matter) in the ocean are complex, and there is a half-century-old enigma about the existence of a huge reservoir of recalcitrant dissolved organic carbon (RDOC) that equates to the magnitude of the pool of atmospheric CO₂. The concepts of the biological carbon pump (BCP) …

Threshold-Dependent Repression Of Spl Gene Expression By Mir156/Mir157 Controls Vegetative Phase Change In Arabidopsis Thaliana, Jia He, Mingli Xu, Matthew R. Willmann, Kevin Mccormick, Tieqiang Hu, Li Yang, Colby G. Starker, Daniel F. Voytas, Blake C. Meyers, R. Scott Poethig

Faculty Publications

Vegetative phase change is regulated by a decrease in the abundance of the miRNAs, miR156 and miR157, and the resulting increase in the expression of their targets, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors. To determine how miR156/miR157 specify the quantitative and qualitative changes in leaf morphology that occur during vegetative phase change, we measured their abundance in successive leaves and characterized the phenotype of mutations in different MIR156 and MIR157 genes. miR156/miR157 decline rapidly between leaf 1&2 and leaf 3 and decrease more slowly after this point. The amount of miR156/miR157 in leaves 1&2 greatly exceeds the …

Spatial Extinction Date Estimation: A Novel Method For Reconstructing Spatiotemporal Patterns Of Extinction And Identifying Potential Zones Of Rediscovery, Colin J. Carlson, Kevin R. Burgio, Tad Dallas, Alexander L. Bond

Faculty Publications

1. The estimation of extinction dates from limited and incomplete sighting records

is a key challenge in conservation (when experts are uncertain whether a species has

gone extinct) and historical ecology (when the date and mechanism of extinction is

controversial).

2. We introduce a spatially-explicit method of interpolating extinction date estima8 tors, allowing users to estimate spatiotemporal surfaces of population persistence 9 from georeferenced sighting data of variable quality.

3. We present the R package spatExtinct, which produces spatially-explicit extinction date surfaces from geolocated sightings, including options for custom randomization schemes to improve accuracy with limited datasets. We use simulations …

Experimental Evidence Of A Pathogen Invasion Threshold, Tad Dallas, Martin Krkošek, John M. Drake

Faculty Publications

Host density thresholds to pathogen invasion separate regions of parameter space corresponding to endemic and disease-free states. The host density threshold is a central concept in theoretical epidemiology and a common target of human and wildlife disease control programmes, but there is mixed evidence supporting the existence of thresholds, especially in wildlife populations or for pathogens with complex transmission modes (e.g. environmental transmission). Here, we demonstrate the existence of a host density threshold for an environmentally transmitted pathogen by combining an epidemiological model with a microcosm experiment. Experimental epidemics consisted of replicate populations of naive crustacean zooplankton (Daphnia dentifera …