Fall 2015 Resources and Publications

Stoichiometric Flexibility in Diverse Aquatic Heterotrophic Bacteria Is Coupled to Differences in Cellular Phosphorus Quotas
Godwin, C. M. and J. B. Cotner. 2015
Frontiers in Microbiology 62015): doi:10.3389/fmicb

We evaluated biomass C:P homeostasis in 24 strains of bacteria isolated from temperate lakes using a uniform relative growth rate in chemostats. Overall, the strains exhibited a range of homeostatic regulation from strong homeostasis to highly flexible biomass stoichiometry, but strains that were isolated using P-rich media formulations were more homeostatic than strains isolated using P-poor media. 

Carbon:phosphorus Homeostasis of Aquatic Bacterial Assemblages Is Mediated by Shifts in Assemblage Composition Godwin, C.M. and J.B. Cotner. 2015
Aquatic Microbial Ecology 73, no. 3 (2014): doi:10.3354/ame01719

Several studies have noted a disparity between the stoichiometric regulation of bacterial assemblages and populations. In response to phosphorus availability, assemblages of bacteria often exhibit greater flexibility in their biomass carbon (C) to phosphorus (P) ratios (C:P) than axenic populations, some of which are homeostatic. We hypothesized that assemblages are inherently non-homeostatic as the result of resource-driven shifts in dominance between more homeostatic strains at low resource C:P ratios and highly flexible strains when P is scarce relative to C.

Aquatic Heterotrophic Bacteria Have Highly Flexible Phosphorus Content and Biomass Stoichiometry
Godwin, C. M. and J. B. Cotner. 2015
The ISME journal (2015)doi:10.1038/ismej.2015.34

Bacteria are central to the cycling of carbon (C), nitrogen (N) and phosphorus (P) in every ecosystem, yet our understanding of how tightly these cycles are coupled to bacterial biomass composition is based upon data from only a few species. Bacteria are commonly assumed to have high P content, low biomass C:P and N:P ratios, and inflexible stoichiometry. Here, we show that bacterial assemblages from lakes exhibit unprecedented flexibility in their P content (3% to less than 0.01% of dry mass) and stoichiometry (C:N:P of 28: 7:1 to more than 8500: 1200: 1)


Species Sorting and Seasonal Dynamics Primarily Shape Bacterial Communities in the Upper Mississippi River
Staley, C., T. J. Gould, P. Wang, J. Phillips, J. B. Cotner, and M. J. Sadowsky. 2015
Sci Total Environ505 (2015): doi:10.1016/j.scitotenv.2014.10.012

Bacterial community structure (BCS) in freshwater ecosystems varies seasonally and due to physicochemical gradients, but metacommunity structure of a major river remains understudied. Here we characterize the BCS along the Mississippi River and contributing rivers in Minnesota over three years using Illumina next-generation sequencing, to determine how changes in environmental conditions as well as inputs from surrounding land and confluences impacted community structure.


Physiological Modifications of Seston in Response to Physicochemical Gradients within Lake Superior 
Bellinger, B. J., A. S. Benjamin, V. Mooy, J. B. Cotner, H. F. Fredricks, C. R. Benitez-Nelson, J. Thompson, A. Cotter, M. L. Knuth, and C. M. Godwin. 2015
Limnology and Oceanography 59, no. 3 (2014): doi:10.4319/lo.2014.59.3.1011

In September 2011, we investigated the distribution and composition of dissolved and particulate phosphorus (P) pools throughout Lake Superior, a large P-limited freshwater ecosystem. Average seston particulate P (PP) concentrations in the deep chlorophyll maximum (DCM; 85 ± 28 nmol L−1) were significantly greater than in the epilimnion (63 ± 22 nmol L−1). In contrast, average particulate organic carbon (POC) : PP (mol : mol) ratios showed the opposite pattern (DCM = 303 : 1 vs. epilimnion = 455 : 1).


Patterns and Drivers of Change in Organic Carbon Burial across a Diverse Landscape: Insights from 116 Minnesota Lakes ;
Dietz, R. D., D. R. Engstrom, and N. J. Anderson. 2015
Global Biogeochem. Cycles, 29, 708–727, doi:10.1002/2014GB004952

Lakes may store globally significant quantities of organic carbon (OC) in their sediments, but the extent to which burial rates vary across space and time is not well described. Using 210Pb-dated sediment cores, we explored patterns of OC burial in 116 lakes spanning several ecoregions and land use regimes in Minnesota, USA during the past 150–200 years.