A survey on the dynamics of bacterioplankton assemblages associated with an estuarine system and the stomodeum of Mnemiopsis leidyi and their functional potential
Type of DegreePhD Dissertation
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Estuaries are among the most biologically productive ecosystems. Eighty percent of our sea food is harvested from estuaries, which are popular recreation areas, yet vital to marine transportation. Unfortunately, estuaries also act as sinks for anthropogenic and natural pollutants. From the viewpoint of ecosystem health, it is important to monitor estuarine ecosystems and their resident organisms, especially those with invasive potential. Chapter 1 provides an introduction to estuarine ecosystems and discusses the major pollutants that affect the dynamics of bacterial assemblages and their functional potential. The impacts of anthropogenic and natural perturbations such as atmospheric deposition of gaseous pollutants, acidification, nutrient loads, bacteria and antibiotic resistance genes and invasive species and their effects are covered. The chapter concludes with an exploration of how to mitigate the impacts of pollution in estuarine ecosystems. Chapter 2 correlates changes in the abiotic, physicochemical parameters of Mobile Bay and changes in dominant bacterial assemblages between wet, cold (January and March) and dry, warm (August and September) months. The study also investigates the differences in the taxonomic, phylogenetic and functional potential of the bacterial assemblages between the two sampling periods, using a metagenomic approach. The study also performs a comparative analysis between Mobile Bay and four other coastal ecosystems. Chapter 3 provides a survey of bacterial assemblages in the stomodeum of the Mnemiopsis leidyi and predicts their functional potential. A comparative analysis between M. leidyi bacterial assemblages and those associated with hosts belonging to two sister phyla (a poriferan and a cnidarian). Chapter 4 examines previously uncharacterized bacterial isolates from the ctenophore M. leidyi that display antibiotic resistance, using genomic, chemotaxonomic and classical microbiology techniques. A new species, Staphylococcus mnemiopsis nov., isolated from the M. leidyi stomodeum, displays antibiotic resistance against the penicillins (Penicillin and Ampicillin), fluoroquinolones (Ciprofloxacin, Nalidixic acid), a polypeptide (Bacitracin) and an aminoglycoside (Kanamycin). The present study reveals aspects of the dynamics of bacterial assemblages in Mobile Bay, and the potential for the ctenophore M. leidyi to harbor bacteria with antibiotic resistance genes. This study could form the basis for future examination of the link between watershed management, estuarine systems and ecosystem health.