Abstracts Biological Sciences

Regulation of the Pho Regulon and Reconstruction of the Photosynthetic Apparatus under Phosphate Limitation in Synechocystis sp. PCC 6803

by Jacob Ryan Irby

For millennia, cyanobacteria have evolved strategies for acclimatization to dynamic environments – this requires a molecular response system. Phosphate is essential for cellular integrity and metabolism, yet inorganic phosphate is often the limiting nutrient for most aquatic environments. This study characterizes two periplasmic phosphate-binding proteins, namely SphX and SphZ, which are essential for the functional response of the SphS-SphR signal transduction system in Synechocystis sp. PCC 6803 and incorporates both into a model. SphX offers a competitive role so as to ensure inorganic phosphate is not depleted from the environment at a faster rate than is necessary for metabolism and, therefore, hinders luxury uptake; whereas, SphZ, encoded by sll0540, is the auxiliary sensor necessary for the SphS response under phosphate limitation in tandem with a protein complex association with the phosphate-specific transport 2 system and the negative regulator, SphU. Cross-regulation between the pho regulon and the photosynthetic apparatus is presented as well as a parameterized analysis for low-temperature fluorescence emission spectroscopy.