Novel Aspects of Phosphorus Metabolism in Thermophilic Cyanobacteria

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Phosphorus is a key component of genetic information, energy metabolism, structural and cell signaling molecules, but is often a limiting nutrient in several important ecosystems. Thus an understanding of how different sources of P (such as phosphates and phosphonates) are acquired and recycled in the environment is of critical importance. Prokaryotes, including cyanobacteria, contribute importantly to the biogeochemical cycling of phosphorus (P), carbon (C) and nitrogen (N) in many environments. Little is known about the total levels of bioavailable P compounds in the terrestrial biosphere and there can be wide variation in different ecosystems. Furthermore, the synthesis and release of phosphonates (which have a stable C-P bond and are therefore not easily degraded) into the environment is quite significant because of their extensive use in various industries. As a consequence many terrestrial and aquatic ecosystems are contaminated. Because P is a key nutrient, bacteria have evolved sophisticated ways to sense and scavenge available sources of P, including phosphonates. Extremophilic cyanobacterial isolates from hot spring mats have a complex P acquisition and metabolism circuitry and also have the capacity to metabolize phosphonates. These environmentally relevant cyanobacteria will be used to dissect and explore questions regarding the regulation of phosphorus/phosphonate utilization and its connection to carbon metabolism and cycling in the environment. Similarities and differences in the utilization of various phosphorus sources using transcript analysis and biochemical assays will be defined. Levels of various P species in the isolates under defined conditions and environmental parameters in the mats will be determined. Targeted mutants of these cyanobacteria has made detailed genetic analysis feasible. Correlating responses under defined conditions and those measured directly in the environment will allow for an understanding of how microbial communities respond and acclimate to phosphorus levels in the environment.Broader ImpactsPhosphorus is often a nutrient that limits growth in marine and terrestrial environments. Conversely, various anthropogenic organophosphorus compounds (insecticides, herbicides etc.) can also be major contaminants in industrial effluents and contribute to the eutrophication of water bodies. Consequently, harmful and unmanageable cyanobacterial and algal blooms have increased in recent years. The insights gained about how cyanobacteria effectively access and metabolize different organophosphorus sources maybe broadly applicable to other photosynthetic microbes, particularly those in the oceans. These findings may also be of some significance in bioremediation studies since there is an indication that phosphonate utilization genes can be transferred laterally across lineages. In the process of developing this research program, undergraduates, graduate students and post-doctoral fellows will be trained. The Carnegie Institution which is located on the campus of Stanford University is dedicated to research and offers excellent training in interdisciplinary research and a well-attended summer intern program. Strong ties with San Jose State University which has a large and diverse student body and with Mills College, Oakland, a historical and well-established women's college, will allow for training of students typically under-represented in science. Finally, since this research involves microbes at Yellowstone National Park, researchers will work with Park authorities to contribute to their extensive and widely used outreach program.