Biology subjects

Jay T Lennon

Publications and source records attributed to Jay T Lennon.

3 recordsLinked to original sources

bioRxiv2015

Microbial contributions to subterranean methane sinks

Understanding the sources and sinks of methane (CH4) is critical for predicting and managing global biogeochemical cycles. Recent studies have reported that CH4 concentrations in cave ecosystems are depleted and that these subterranean environments may act as a daily sinks for atmospheric CH4. It has been hypothesized that this CH4 depletion may be caused by radiolysis, an abiotic process whereby CH4 is oxidized via interactions with ionizing radiation derived from radon decay. Alternatively, the depletion of CH4 concentrations could be due to biological processes, specifically oxidation by methanotrophic bacteria. We theoretically explored the radiolysis hypothesis and conclude that it is a kinetically constrained process that is unlikely to lead to the rapid loss of CH4 in subterranean environments. We present experimental results to support this claim. We tested the microbial oxidation hypothesis in a set of mesocosm experiments that were conducted in Vietnamese caves. Our results reveal that methanotrophic bacteria associated with cave rocks consume CH4 at a rate of 1.33 - 2.70 mg CH4 {middle dot} m-2 {middle dot} d-1. These CH4 oxidation rates equal or exceed what has been reported in other habitats, including agricultural systems, grasslands, deciduous forests, and Arctic tundra. As such, microbial methanotrophy has the potential to significantly oxidize CH4 in caves, but also smaller-size open subterranean spaces, such as cracks, fissures, and other pores that are connected to and rapidly exchange with the atmosphere. Future studies are needed to understand how subterranean CH4 oxidation scales up to affect regional and global CH4 cycling.

Ecology↗

bioRxiv2015

Species sorting along a subsidy gradient alters community stability

The movement of resources between terrestrial and aquatic habitats has strong effects on ecological processes in recipient ecosystems. Allochthonous inputs modify the quality and quantity of the available resource pool in ways that may alter the composition and stability of recipient communities. Inputs of terrestrial dissolved organic carbon (tDOC) into aquatic ecosystems represent a large influx of resources that has the potential to affect local communities, especially microorganisms. To evaluate the effects terrestrial inputs on aquatic microbial community composition and stability, we manipulated the supply rate of tDOC to a set of experimental ponds. Along the tDOC supply gradient, we measured changes in diversity and taxon-specific changes in abundance and activity. We then determined community stability by perturbing each pond using a pulse of inorganic nutrients and measuring changes in composition and activity (i.e., responsiveness) along the gradient. Terrestrial DOC supply significantly altered the composition of the active microbial community. The composition of the active bacterial community changed via decreases in richness and evenness as well as taxon-specific changes in abundance and activity indicating species sorting along the gradient. Likewise, the responsiveness of the active bacterial community decreased along the gradient, which led to a more stable active community. We did not, however, observe these changes in diversity and stability in the total community (i.e., active and inactive organisms), which suggests that tDOC supply modifies microbial community stability through functional not structural changes. Together, these results show that altered aquatic terrestrial linkages can have profound effects on the activity and stability of the base of the food web and thus can alter ecosystem functioning.

Ecology↗

bioRxiv2015

Crop diversity enhances disease suppressive potential in soils

Microbiomes can aid in the protection of hosts from infection and disease, but the mechanisms underpinning these functions in complex environmental systems remain unresolved. Soils contain microbiomes that influence plant performance, including their susceptibility to disease. For example, some soil microorganisms produce antimicrobial compounds that suppress the growth of plant pathogens, which can provide benefits for sustainable agricultural management. Evidence shows that crop rotations increase soil fertility and tend to promote microbial diversity, and it has been hypothesized that crop rotations can enhance disease suppressive capacity, either through the influence of plant diversity impacting soil bacterial composition or through the increased abundance of disease suppressive microorganisms. In this study, we used a long-term field experiment to test the effects of crop diversity through time (i.e., rotations) on soil microbial diversity and disease suppressive capacity. We sampled soil from seven treatments along a crop diversity gradient (from monoculture to five crop species rotation) and a spring fallow (non-crop) treatment to examine crop diversity influence on soil microbiomes including bacteria that are capable of producing antifungal compounds. Crop diversity significantly influenced bacterial community composition, where the most diverse cropping systems with cover crops and fallow differed from bacterial communities in the 1-3 crop species diversity treatments. While soil bacterial diversity was about 4% lower in the most diverse crop rotation (corn-soy-wheat + 2 cover crops) compared to monoculture corn, crop diversity increased disease suppressive functional group prnD gene abundance in the more diverse rotation by about 9% compared to monocultures. Identifying patterns in microbial diversity and ecosystem function relationships can provide insight into microbiome management, which will require manipulating soil nutrients and resources mediated through plant diversity.

Microbiology↗