Publication Date: 2012.
The aim of this work was to identify closely related rhizobia, used to formulate commercial inoculants, using polymerase chain reaction (PCR). Repetitive extra-genic palindromic (REP) and BOX fingerprints hardly discriminate among a set of commercial strains. PCR targeted at repetitive RSα successfully allow discriminating within representatives of Bradyrhizobium. These fingerprints clustered isolates at a higher level of similarity and proved to be an important tool to complement the information provided by the other markers. The results suggest that mutants occur along the bacterial culture, during inoculant production. However, independently of the number of amplification reactions used to characterize and identify organisms, mispriming always generates artifactual diversity. In addition to this, it seems that combining reactions such as BOX or REP fingerprinting with reactions targeted at the RSα sequence, generates a more reliable identification tool to characterize closely related bradyrhizobia.
Facultad de Ciencias Agrarias y Forestales
Keywords: Ciencias Agrarias; bacterial DNA; article; artifact; bacterial strain; bacterium culture; bacterium identification; bacterium isolate; bacterium mutant; Bradyrhizobium; Bradyrhizobium elkanii; Bradyrhizobium japonicum; controlled study; DNA fingerprinting; gene amplification; inoculation; nonhuman; polymerase chain reaction; soybean; Bacteria (microorganisms); Bradyrhizobiaceae; Bradyrhizobium; Glycine max; inoculant; molecular markers; rhizobia.
Repository: SEDICI (UNLP). Universidad Nacional de La Plata
Publication Date: 2007.
Polyhydroxyalkanoates (PHAs) are accumulated as intracellular granules by many bacteria under unfavorable conditions, enhancing their fitness and stress resistance. Poly(3-hydroxybutyrate) (PHB) is the most widespread and best-known PHA. Apart from the genes that catalyze polymer biosynthesis, natural PHA producers have several genes for proteins involved in granule formation and/or with regulatory functions, such as phasins, that have been shown to affect polymer synthesis. This study evaluates the effect of PhaP, a phasin, on bacterial growth and PHB accumulation from glycerol in bioreactor cultures of recombinant Escherichia coli carrying phaBAC from Azotobacter sp. strain FA8. Cells expressing phaP grew more, and accumulated more PHB, both using glucose and using glycerol as carbon sources. When cultures were grown in a bioreactor using glycerol, PhaP-bearing cells produced more polymer (2.6 times) and more biomass (1.9 times) than did those without the phasin. The effect of this protein on growth promotion and polymer accumulation is expected to be even greater in high-density cultures, such as those used in the industrial production of the polymer. The recombinant strain presented in this work has been successfully used for the production of PHB from glycerol in bioreactor studies, allowing the production of 7.9 g/liter of the polymer in a semisynthetic medium in 48-h batch cultures. The development of bacterial strains that can efficiently use this substrate can help to make the industrial production of PHAs economically feasible. Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Author affiliation: De Almeida, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Author affiliation: Pettinari, M.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Keywords: Bacteria; Biomass; Bioreactors; Biosynthesis; Escherichia coli; Glycerol; Intracellular granules; Polyhydroxyalkanoates (PHAs); Semisynthetic medium; Stress resistance; Proteins; bacterial protein; carbon; glucose; glycerol; poly(3 hydroxybutyric acid); polyhydroxyalkanoic acid; polymer; regulator protein; bacterium; fitness; gene; growth; polymer; protein; stress resistance; article; Azotobacter; bacterial growth; bacterial strain; bacterium culture; bioreactor; biosynthesis; catalysis; cell granule; controlled study; Escherichia coli; nonhuman; protein expression; protein function; stress; Azotobacter; Bacterial Proteins; Biomass; Bioreactors; DNA-Binding Proteins; Escherichia coli; Fermentation; Glucose; Glycerol; Hydroxybutyrates; Polyesters; Azotobacter; Bacteria (microorganisms); Escherichia coli.
Repository: Biblioteca Digital (UBA-FCEN). Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales