Meet The Microbiologist - The Scientists Behind The Microbiology

The most abundant organism on Earth lives in its seas: the marine bacterium SAR11. Steve Giovannoni describes how the origins of SAR11 provided its name, and the ways that studying SAR11 have taught scientists about ocean ecology. He also discusses how the different depths of the ocean vary in their microbial compositions and what his big questions are in marine microbiology. Different depths of the ocean have different habitats, but the microbes vary continuously, based in part on light availability: Surface light facilitates photosynthesis by algal cells. These primary producers fix carbon for the entire ecosystem! Because nutrients are readily available, the cell concentration in surface waters can reach nearly 1,000,000 cells/ml. The twilight zone offers dim light. Microbes in this area mainly use carbon sources generated by the surface-dwelling microbes. Below a few hundred meters, cell concentrations drop to 10,000-100,000 cells/ml. The deep ocean has no light and the microbes that live here have signi