Augustana College (Illinois)

About: Augustana College (Illinois) is a education organization based out in Rock Island, Illinois, United States. It is known for research contribution in the topics: Higher education & Population. The organization has 491 authors who have published 763 publications receiving 14274 citations. The organization is also known as: Augustana College and Theological Seminary.

Profiling Myxococcus xanthus Swarming Phenotypes through Mutation and Environmental Variation.

Abstract: Myxococcus xanthus is a bacterium that lives on surfaces as a predatory biofilm called a swarm. As a growing swarm feeds on prey and expands, it displays dynamic multicellular patterns such as traveling waves called ripples and branching protrusions called flares. The rate at which a swarm expands across a surface, and the emergence of the coexisting patterns, are all controlled through coordinated cell movement. M. xanthus cells move using two motility systems known as adventurous (A) and social (S). Both are involved in swarm expansion and pattern formation. In this study, we describe a set of M. xanthus swarming genotype-to-phenotype associations that include both genetic and environmental perturbations. We identified new features of the swarming phenotype, recorded and measured swarm expansion using time-lapse microscopy, and compared the impact of mutations on different surfaces. These observations and analyses have increased our ability to discriminate between swarming phenotypes and provided context that allows us to identify some phenotypes as improbable outliers within the M. xanthus swarming phenome. IMPORTANCE Myxococcus xanthus grows on surfaces as a predatory biofilm called a swarm. In nature, a feeding swarm expands by moving over and consuming prey bacteria. In the laboratory, a swarm is created by spotting cell suspension onto nutrient agar in lieu of prey. The suspended cells quickly settle on the surface as the liquid is absorbed into the agar, and the new swarm then expands radially. An assay that measures the expansion rate of a swarm of mutant cells is the first, and sometimes only, measurement used to decide whether a particular mutation impacts swarm motility. We have broadened the scope of this assay by increasing the accuracy of measurements and introducing prey, resulting in new identifiable and quantifiable features that can be used to improve genotype-to-phenotype associations.

Correction to “Linking the 8.2 ka event and its freshwater forcing in the Labrador Sea”

Abstract: [1] The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in dO of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that 3 C of near-surface ocean cooling masked an 1.0‰ decrease in western Labrador Sea dO of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic dO of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event. Citation: Hoffman, J. S., A. E. Carlson, K. Winsor, G. P. Klinkhammer, A. N. LeGrande, J. T. Andrews, and J. C. Strasser (2012), Linking the 8.2 ka event and its freshwater forcing in the Labrador Sea, Geophys. Res. Lett., 39, L18703, doi:10.1029/ 2012GL053047.

Spatial changes in the hydrology of portions of the twin cities, minnesota: a simulation study

Abstract: A physically based, distributed model called SIRWAT (Spatially Integrated Regional Watershed Analysis Tool) has been designed to simulate water-resource changes in intermediate-scale basins undergoing change due to urban expansion. This water-yield model overcomes several limitations in current simulations through its integration with a geographic information system (GIS) and use of an expanded groundwater model for complex, multi-layered subsurface situations. A typical simulation consists of one or more watersheds with a combined area between 100 and 10,000 km2, and response units of a square kilometer or larger. Input parameters do not require calibration, which allows the model to be applied in a variety of geographic situations. Analysis of the Nine Mile Creek basin in the Twin Cities Metropolitan Area (TCMA) of Minnesota, USA, illustrates the magnitude of change (e.g., annual increases of surface runoff from 23 to 64 percent, and losses of groundwater recharge from 25 to 50 percent) and spatial vari...