Nostoc punctiforme is a filamentous cyanobacterium capable of differentiation into motile hormogonia, nitrogen-fixing heterocysts, and spore-like dormant cells called akinetes. It serves as a model system for studying development due to its one-dimensional body plan, sequenced genome, facile genetic system, and a working DNA microarray. This study focuses on identifying and characterizing genes involved with akinete development. Akinetes can withstand environmental stress, such as desiccation and cold that kill normal vegetative cells within the filament. The first specific aim is to 1) identify members of the regulon controlled by an ECF sigma factor involved in akinete formation, and 2) to determine if its activity is controlled by an associated anti-sigma factor.
Specific aim 2 will exhaustively test genes encoding putative DNA regulatory proteins that were identified in a previous DNA microarray for 1) akinete-specific expression using GFP reporters, and 2) akinete-involvement through the use of mutant analysis. Defective mutants in akinete formation or function will be further characterized genetically and phenotypically. Identification of genes involved in akinete formation will likely give insights into possibly novel mechanisms by which bacteria gain resistance to environmental stress. Additionally, this work will involve underrepresented students at CSU Northridge who will be trained using cutting-edge technology applicable to many aspects of the biomedical sciences.

Public Health Relevance

Nostoc punctiforme is a simple model system used to study cellular differentiation from vegetative cells into dormant akinete cells that are resistant to environmental extremes. Knowledge of regulatory events essential for akinete formation will aid in understanding how more pathogenic bacteria gain resistance to environmental stress. Related cyanobacteria cause toxic blooms in water systems and persist in the environment as akinetes. Understanding akinete formation may identify targets to inhibit their formation or germination, thereby reducing survival and the extent of subsequent toxic blooms by toxic cyanobacteria.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Enhancement Award (SC1)
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Special Emphasis Panel (ZGM1-MBRS-X (GC))
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Reddy, Michael K
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California State University Northridge
Schools of Arts and Sciences
United States
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Ricci, J N; Morton, R; Kulkarni, G et al. (2017) Hopanoids play a role in stress tolerance and nutrient storage in the cyanobacterium Nostoc punctiforme. Geobiology 15:173-183
Bell, Nicole; Lee, Jamie J; Summers, Michael L (2017) Characterization and in vivo regulon determination of an ECF sigma factor and its cognate anti-sigma factor in Nostoc punctiforme. Mol Microbiol 104:179-194
Peramuna, Anantha; Summers, Michael L (2014) Composition and occurrence of lipid droplets in the cyanobacterium Nostoc punctiforme. Arch Microbiol 196:881-90
Holmquist, Peter C; Holmquist, Gerald P; Summers, Michael L (2011) Comparing binding site information to binding affinity reveals that Crp/DNA complexes have several distinct binding conformers. Nucleic Acids Res 39:6813-24