Community-level analysis of phototrophy: psbA gene diversity

Photosynthetic organisms play a crucial role in the marine environment. In vast areas of the oceans, most of this marine production is performed by cells smaller than 2-3 μm (picoplankton). This chapter describes molecular analyses of the conserved photosynthetic psbA gene (protein D1 of photosystem II reaction center) as a diversity indicator of naturally occurring marine oxygenic picophytoplankton and of marine cyanophages carrying photosynthesis genes.