In the light of the recent developments in the field of marine microbial ecology the course will give an overview on structure and function of microbial communities in the oceans including discussions on novel methods, results and hypotheses. Among the topics covered are: Photoheterotrophic bacteria, Marine Bacteria and the Carbon Cycle, UV radiation effects on Microbes and Microbial Processes, Uptake and Regeneration of Inorganic Nutrients by Marine Heterotrophic Bacteria, Bacterivory: Interactions between Bacteria and their Grazers, Symbiosis and Mixotrophy Among Pelagic Microorganisms, Marine Viruses and their ecological impact, Global Ocean Survey of Marine Metagenomics, Single cell activity in marine bacterioplankton. Marine extreme environments and microbial extremophiles; Major marine extreme environments (e.g. Mangroves, Deep sea anoxic brine pools; hydrothermal vents); Microbial adaptation to extremes (salinity, thermal adaptation, etc); archaea; metabolic diversity and networks; Element cycles in extreme ecosystems; Sediment microbiomes; The diversity and mechanisms of symbiotic interactions between marine hosts and microbes; As a Ph.D. level course, assessment of students and participation expectations will be commensurate with the level of student experience.