Open Access Research article

Identification and characterization of PhbF: A DNA binding protein with regulatory role in the PHB metabolism of Herbaspirillum seropedicae SmR1

Marco AS Kadowaki1, Marcelo Müller-Santos1, Fabiane GM Rego2, Emanuel M Souza1, Marshall G Yates1, Rose A Monteiro1, Fabio O Pedrosa1, Leda S Chubatsu1 and Maria BR Steffens1*

Author Affiliations

1 Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba - PR, Brazil

2 Department of Medical Pathology, Universidade Federal do Paraná, Curitiba - PR, Brazil

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BMC Microbiology 2011, 11:230  doi:10.1186/1471-2180-11-230

Published: 14 October 2011



Herbaspirillum seropedicae SmR1 is a nitrogen fixing endophyte associated with important agricultural crops. It produces polyhydroxybutyrate (PHB) which is stored intracellularly as granules. However, PHB metabolism and regulatory control is not yet well studied in this organism.


In this work we describe the characterization of the PhbF protein from H. seropedicae SmR1 which was purified and characterized after expression in E. coli. The purified PhbF protein was able to bind to eleven putative promoters of genes involved in PHB metabolism in H. seropedicae SmR1. In silico analyses indicated a probable DNA-binding sequence which was shown to be protected in DNA footprinting assays using purified PhbF. Analyses using lacZ fusions showed that PhbF can act as a repressor protein controlling the expression of PHB metabolism-related genes.


Our results indicate that H. seropedicae SmR1 PhbF regulates expression of phb-related genes by acting as a transcriptional repressor. The knowledge of the PHB metabolism of this plant-associated bacterium may contribute to the understanding of the plant-colonizing process and the organism's resistance and survival in planta.