Kelp microbiology: linking bacteria and viruses to carbon cycling within kelp forests

Kelps are large marine algae that use photosynthesis to convert carbon dioxide into organic carbon which they store as biomass. This organic carbon represents a major energy source for many of the other organisms in the ecosystem. Due to this conversion and their large biomass, kelp forests are among the most productive ecosystems on the planet yet very little of the kelp carbon enters the food web by direct grazing on the kelp itself. In fact, bacteria liberate a majority (70-80%) of the carbon in kelp making it available for consumption by other organisms via a pathway called the microbial loop. However, little is understood about the movement and cycling of kelp carbon through this loop. As part of a larger project designed to determine the importance of viruses in cycling kelp carbon, we isolated several (7) marine bacteria that use kelp carbon for growth. Using standard microbial techniques, we grew these bacterial cultures, classified them using colony and cell morphology and determined aspects of their metabolic capabilities by testing for the presence of enzymes that catalyze specific metabolic reactions. Furthermore, in a following experiment we examined the application of a Most-Probable-Number assay to determine the ability of viruses to infect our isolated bacteria. We observed infections in one of the two tested bacterial cultures (2B5). This result clearly indicates the potential of using this assay in future experiments to quantify the number of viruses present in a seawater sample that can infect bacteria growing on kelp carbon and thus will allow for a deeper understanding of how microbes are ultimately driving the high productivity found in kelp forests.