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Kirtland, OH, United States

Welsh A.K.,Texas State University | Burke D.J.,The Holden Arboretum | Hamerlynck E.P.,U.S. Department of Agriculture | Hahn D.,Texas State University
Plant and Soil

Seasonal variation of arbuscular mycorrhizal fungi (AMF) in roots of the high salt marsh plant Spartina patens, the diversity of nitrogen-fixing bacteria in the rhizosphere and plant growth performance was studied at key stages of the growing season coinciding with major plant phenological stages, i.e., vegetative growth, reproduction and senescence. AMF colonization was highest during vegetative growth, with values declining during the growing season to the same level seen at plant dormancy. AMF colonization was reduced at lower depths in the sediments where anoxic conditions were observed and in plants treated with the systemic fungicide Benomyl. Only small changes in diversity of nitrogen-fixing bacteria in general and more specifically of those belonging to the ε-subdivision of Proteobacteria were detected during the season or between treatments by PCR-RFLP of nifH gene fragments with DNA as template for amplification; however, greater seasonal changes were displayed when cDNA was used as template for amplification as a proxy for gene expression and thus active bacteria. DGGE analyses of nifH gene fragments representing nitrogen-fixing bacteria of the ε-subdivision of Proteobacteria using both using DNA and cDNA as template showed highly diverse profiles that changed during the season and in response to treatment. Seasonal changes were observed for a suite of plant growth attributes and differences were observed between treatments, with higher values generally obtained on non-treated plants compared to Benomyl-treated plants. These differences were most pronounced during vegetative growth; however, differences between non-treated and Benomyl-treated plants were reduced seasonally and disappeared by the onset of senescence. This study demonstrates seasonal changes in AMF colonization on S. patens and in the community structure of nitrogen-fixing members of the ε-subdivision of Proteobacteria in the plant root zone. Plant growth performance changed seasonally with some effects of Benomyl-treatment. © Springer Science + Business Media B.V. 2009. Source

Gupta V.,University of Toronto | Smemo K.A.,The Holden Arboretum | Smemo K.A.,Kent State University | Yavitt J.B.,Cornell University | Basiliko N.,University of Toronto
Microbial Ecology

The active methanotroph community was investigated in two contrasting North American peatlands, a nutrient-rich sedge fen and nutrient-poor Sphagnum bog using in vitro incubations and 13C-DNA stable-isotope probing (SIP) to measure methane (CH 4) oxidation rates and label active microbes followed by fingerprinting and sequencing of bacterial and archaeal 16S rDNA and methane monooxygenase (pmoA and mmoX) genes. Rates of CH 4 oxidation were slightly, but significantly, faster in the bog and methanotrophs belonged to the class Alphaproteobacteria and were similar to other methanotrophs of the genera Methylocystis, Methylosinus, and Methylocapsa or Methylocella detected in, or isolated from, European bogs. The fen had a greater phylogenetic diversity of organisms that had assimilated 13C, including methanotrophs from both the Alpha- and Gammaproteobacteria classes and other potentially non-methanotrophic organisms that were similar to bacteria detected in a UK and Finnish fen. Based on similarities between bacteria in our sites and those in Europe, including Russia, we conclude that site physicochemical characteristics rather than biogeography controlled the phylogenetic diversity of active methanotrophs and that differences in phylogenetic diversity between the bog and fen did not relate to measured CH 4 oxidation rates. A single crenarchaeon in the bog site appeared to be assimilating 13C in 16S rDNA; however, its phylogenetic similarity to other CO 2-utilizing archaea probably indicates that this organism is not directly involved in CH 4 oxidation in peat. © 2011 Springer Science+Business Media, LLC. Source

Krynak K.L.,Case Western Reserve University | Burke D.J.,The Holden Arboretum | Benard M.F.,Case Western Reserve University
Biological Conservation

Due to ease of global transportation, disease threats to amphibians are expected to increase. Therefore it is crucial that we improve our understanding of factors which may depress disease resistance so that we can incorporate this information into long-term conservation planning. Amphibians are protected from disease-causing pathogens by two skin-associated immune defense traits: the skin microbiome and the antimicrobial peptides found within natural peptide secretions (NPS) produced by the skin. Particular environmental characteristics may alter these amphibian immune defense traits and potentially affect disease resistance. We surveyed the skin-associated microbial communities (microbiome) and natural peptide secretions (NPS) of Blanchard's cricket frogs (. Acris blanchardi), at each of eleven sites across the species' declining range. We utilized an AICc model selection and model averaging approach to test for potential environmental influence on these traits. We found that populations differed in microbiomes and NPS production, but not NPS bioactivity against Bd (. Batrachochytrium dendrobatidis). The microbiome was associated with water conductivity, ratio of natural to managed land, and latitude. Additionally the microbiome was affected by interactions between frog sex and latitude, between frog sex and water surface area, and between the ratio of natural to managed land and water surface area. NPS production was influenced by an interaction between water surface area and conductivity. We found no evidence that NPS influence the microbiome; however, Bd growth rate in culture was positively associated with NPS production. This study indicates that environmental characteristics influence amphibian immune defense traits and may explain population differences in pathogen resistance. © 2015 Elsevier Ltd. Source

Becklin K.M.,University of Kansas | Medeiros J.S.,The Holden Arboretum | Sale K.R.,University of Kansas | Ward J.K.,University of Kansas
Ecology Letters

Assessing family- and species-level variation in physiological responses to global change across geologic time is critical for understanding factors that underlie changes in species distributions and community composition. Here, we used stable carbon isotopes, leaf nitrogen content and stomatal measurements to assess changes in leaf-level physiology in a mixed conifer community that underwent significant changes in composition since the last glacial maximum (LGM) (21 kyr BP). Our results indicate that most plant taxa decreased stomatal conductance and/or maximum photosynthetic capacity in response to changing conditions since the LGM. However, plant families and species differed in the timing and magnitude of these physiological responses, and responses were more similar within families than within co-occurring species assemblages. This suggests that adaptation at the level of leaf physiology may not be the main determinant of shifts in community composition, and that plant evolutionary history may drive physiological adaptation to global change over recent geologic time. © 2014 John Wiley & Sons Ltd/CNRS. Source

Preston M.D.,University of Toronto | Smemo K.A.,The Holden Arboretum | Smemo K.A.,Kent State University | McLaughlin J.W.,Ontario Ministry of Natural Resources | Basiliko N.,University of Toronto
Frontiers in Microbiology

Northern peatlands are a large repository of atmospheric carbon due to an imbalance between primary production by plants and microbial decomposition. The James Bay Lowlands (JBL) of northern Ontario are a large peatland-complex but remain relatively unstudied. Climate change models predict the region will experience warmer and drier conditions, potentially altering plant community composition, and shifting the region from a long-term carbon sink to a source. We collected a peat core from two geographically separated (ca. 200 km) ombrotrophic peatlands (Victor and Kinoje Bogs) and one minerotrophic peatland (Victor Fen) located nearVictor Bog within the JBL. We characterized (i) archaeal, bacterial, and fungal community structure with terminal restriction fragment length polymorphism of ribosomal DNA, (ii) estimated microbial activity using community level physiological profiling and extracellular enzymes activities, and (iii) the aeration and temperature dependence of carbon mineralization at three depths (0-10, 50-60, and 100-110 cm) from each site. Similar dominant microbial taxa were observed at all three peatlands despite differences in nutrient content and substrate quality. In contrast, we observed differences in basal respiration, enzyme activity, and the magnitude of substrate utilization, which were all generally higher at Victor Fen and similar between the two bogs. However, there was no preferential mineralization of carbon substrates between the bogs and fens. Microbial community composition did not correlate with measures of microbial activity but pH was a strong predictor of activity across all sites and depths. Increased peat temperature and aeration stimulated CO2 production but this did not correlate with a change in enzyme activities. Potential microbial activity in the JBL appears to be influenced by the quality of the peat substrate and the presence of microbial inhibitors, which suggests the existing peat substrate will have a large influence on future JBL carbon dynamics. © 2012 Preston, Smemo, McLaughlin and Basiliko. Source

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