| This dissertation focused on the examination of bacterial communities using both cultivation and molecular characterization methods, with particular emphasis on members of the actinomycetes. Two important components in the success of bacteria were evaluated, the ability to produce bioactive molecules and the ability to thrive in extreme and isolated environments. Factors that potentially influence community structure and function, such as bacteriophages, were also examined. Within each chapter, specific questions and hypotheses regarding the role of the microorganisms being studied were addressed, providing a solid foundation for future studies. Chapter 1 focused on examining the genetic diversity of bacteriophages infecting Streptomyces, resulting in a gain of knowledge about the distribution and diversity of Streptomyces bacteriophages. Chapter 2 introduced the molecular methods used to characterize the bacterial communities associated with iron (Fe) flocculent mats and sediment samples collected from two hydrothermal vent seamounts along the Kermadec arc. Chapter 3 focused on another unusual marine environment, marine caves. Both cultivation and molecular methods were combined to compare cultivable actinomycete communities within shallow coral reef and marine cave sediments. Molecular methods were then utilized to evaluate genes involved in the biosynthesis of bioactive metabolites. Insight into microbial community variation at hydrothermal vent sites and marine caves was obtained. In Chapter 4 the potentially detrimental role of microbially produced bioactive metabolites was analyzed. Several species of Streptomyces were evaluated for the ability to cause degeneration of dopaminergic neurons in a C. elegans model. Actinomycetes were shown to contain not only potentially beneficial bioactive molecules, but also harmful metabolites. These findings have significant impact in a variety of scientific disciplines. These include biomedical, ecological, and geomicrobial implications. |
