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Polyamine Transformation by Bacterioplankton in Freshwater Ecosystems

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2017, MS, Kent State University, College of Arts and Sciences / Department of Biological Sciences.
Polyamines, such as putrescine, play a vital role in marine dissolved organic nitrogen (DON) cycling, but their significance in freshwaters DON cycling has yet to be assessed. To address this knowledge gap, we examined the potential contribution of polyamine turnover rate to DON flux and the effect of dissolved polyamines on the composition of bacterioplankton communities in two freshwater lakes. To measure polyamine concentrations and turnover rates, water samples were collected in summer 2012 from 21 coastal-to-offshore transects along the southern coast of Lake Erie. A number of physicochemical variables and concentrations of polyamines and dissolved free amino acids were measured in water samples. Radioisotope assays were performed with whole (particle-associated bacterioplankton community) and filtered (free-living bacterioplankton community) lake water to estimate bacterial activity and turnover rates of polyamines. All five common polyamines were measured in each of the lake samples. Among the five PAs, putrescine and spermidine appeared to be the most abundant polyamine compounds. The ratio between dissolved free amino acid and polyamine concentrations were around 2:1. This was higher than the marine environments (1:10). The concentrations, turnover rates, and, fluxes of polyamines decreased from the western basin (eutrophic) to the central and eastern basins (oligotrophic). Each of these basins was consistently correlated with primary productivity of the lake. Additionally, the results also showed that putrescine alone accounted for 9.9% of the bacterial nitrogen demand and 4.8% of the bacterial carbon demand. All the above results indicate the importance of polyamines towards the DON cycling in the lake, similar to marine environments. To further evaluate the importance of polyamines for freshwater DON flux and examine the effects of exogenous polyamines on bacterioplankton community structure, water samples were taken from sites in Lake Erie (LE) and Grand Lake St. Marys (GLSM) in July 2012. Concentrations, turnover rates and fluxes of polyamines and dissolved free amino acids were also measured. Response of free-living bacterioplankton community to elevated supply of polyamines was tracked with terminal restriction fragment length polymorphism analysis. Correlations of the primary productivity with concentrations, turnover rates, and, fluxes were again revealed for samples within each lake. Between the two lakes, the same trend was observed, with higher values of primary productivities and concentration, turnover rate, and, fluxes in GLSM than LE. Bacterioplankton community amended with elevated polyamines showed significant growth and consumption of the amended component, indicating that it can serve as a good source of C, N and/or energy for freshwater bacterioplankton. However, terminal restriction fragment polymorphism (T-RFLP) analysis of the 16S rRNA genes showed no significant shift of bacterioplankton communities in either LE or GLSM samples after polyamine amendments. These results indicate that a diverse bacterioplankton community was responsive to polyamines in these freshwater environments.
Xiaozhen Mou (Advisor)
103 p.

Recommended Citations

Citations

  • Madhuri, S. (2017). Polyamine Transformation by Bacterioplankton in Freshwater Ecosystems [Master's thesis, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent150114771851742

    APA Style (7th edition)

  • Madhuri, Sumeda. Polyamine Transformation by Bacterioplankton in Freshwater Ecosystems. 2017. Kent State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent150114771851742.

    MLA Style (8th edition)

  • Madhuri, Sumeda. "Polyamine Transformation by Bacterioplankton in Freshwater Ecosystems." Master's thesis, Kent State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent150114771851742

    Chicago Manual of Style (17th edition)