Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Assessment of Genetic and Functional Relationship of Antagonistic Fluorescent Pseudomonads of Rice Rhizosphere by Repetitive Sequence, Protein Coding Sequence and Functional Gene Analyses: Jayakumar Pathma , Niraikulam Ayyadurai , Natarajan Sakthivel; J. Microbiol. 2010;48(6):715-727. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0064-3

Abstract: Antagonistic fluorescent pseudomonads isolated from rice rhizospheric soil were characterized using biochemical, taxonomical and molecular tools. Production of cyclopropane fatty acid (CFA) was correlated with their antagonistic potential. Strains were grouped into 18 different genotypes on the basis of amplified ribosomal DNA restriction analysis (ARDRA) and repetitive (rep)-PCR based genotypic fingerprinting analyses. High phylogenetic resolution among antagonistic fluorescent pseudomonad strains was obtained based on the DNA gyrase B subunit (gyrB) and RNA polymerase sigma factor 70 (rpoD) gene sequence analyses. Combined gyrB and rpoD sequence analysis resulted in the accurate estimation of molecular phylogeny and provided a significant correlation between the genetic distances among strains. Present study demonstrated the genetic and functional relationship of fluorescent pseudomonads. The knowledge on genetic and functional potential of fluorescent pseudomonads associated with rice rhizosphere is useful to understand their ecological role and for their utilization in sustainable agriculture.

Differential Response of Etiolated Pea Seedlings to Inoculation with Rhizobacteria Capable of Utilizing 1-Aminocyclopropane-1-Carboxylate or L-Methionine: Baby Shaharoona , Muhammad Arshad , Azeem Khalid; J. Microbiol. 2007;45(1):15-20.; DOI: https://doi.org/2497 [pii]

Abstract: The majority of soil microorganisms can derive ethylene from L-methionine (L-MET), while some rhizobacteria can hydrolyze 1-aminocyclopropane-1-carboxylate (ACC) due to their ACC-deaminase activity. In this study, three strains having either ACC-deaminase activity (Pseudomonas putida biotype A, A7), or the ability to produce ethylene from L-MET (Acinetobacter calcoaceticus, M9) or both (Pseudomonas fluorescens, AM3) were used for inoculation. The highly ethylene specific bioassay of a classical “triple” response in pea seedlings was used to investigate the effect of the inoculation with the rhizobacteria in the presence of 10 mM ACC or L-MET. The exogenous application of ACC had a concentration-dependent effect on the etiolated pea seedlings in creating the classical “triple” response. The inoculation with P. putida diluted the effect of ACC, which was most likely due to its ACC-deaminase activity. Similarly, the application of Co2+ reduced the ACC-imposed effect on etiolated pea seedlings. In contrast, the inoculation of A. calcoaceticus or P. fluorescens in the presence of L-MET caused a stronger classical “triple” response in etiolated pea seedlings; most likely by producing ethylene from L-MET. This is the first study, to our knowledge, reporting on the comparative effect of rhizobacteria capable of utilizing ACC vs L-MET on etiolated pea seedlings.

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