Characterization of a new isolate of Pseudomonas fluorescens strain Psd as a potential biocontrol agent.
OBJECTIVE
Evaluation of a new isolate of Pseudomonas fluorescens for its biocontrol properties.


RESULTS
Strain Psd identified as Ps. fluorescens, produces secondary metabolites that are toxic to some plant-pathogenic fungi. Inhibition of fungal growth of Fusarium oxysporum and Verticillium dahliae in the presence of bacterial culture filtrate provided the first clue to its biocontrol properties. In order to determine the basis for antifungal properties, antibiotics were extracted and analysed by TLC. Both pyrrolnitrin and phenazines could be detected in the culture of Psd. Presence of response regulator gene gacA of the two component regulatory system (GacS/GacA) was established by PCR amplification and sequencing. Sequence comparison of gacA justified the taxonomic position of this strain among the known members of Pseudomonadaceae. Synthesis of other compounds like toxic lipodepsipeptide, siderophores, and HCN was also confirmed by appropriate biochemical tests.


CONCLUSIONS
Characterization of strain Psd by various biochemical/plate tests followed by chromatographic identification of antibiotics, demonstrates its multifunctional biocontrol property. Response regulator gene gacA provides an additional genetic marker for the phylogenetic studies.


CONCLUSIONS
Ps. fluorescens strain Psd with its multifunctional biocontrol property can be used to bioprotect the crop plants from phytopathogens.
Upadhyay
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A
Department of Genetics, University of Delhi South Campus, New Delhi, India.
Srivastava
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S
D000898:Antibiosis; D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002855:Chromatography, Thin Layer; D047630:Depsipeptides / Q000378:metabolism; D005670:Fusarium / Q000187:drug effects / Q000254:growth & development*; D006856:Hydrogen Cyanide / Q000378:metabolism; D010572:Pest Control, Biological / Q000379:methods*; D010619:Phenazines / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010802:Phylogeny; D011551:Pseudomonas fluorescens / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology*; D011764:Pyrrolnitrin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000378:metabolism; D020172:Verticillium / Q000187:drug effects / Q000254:growth & development*
D000935:Antifungal Agents; D001426:Bacterial Proteins; D047630:Depsipeptides; C091100:GacA protein, Bacteria; D010619:Phenazines; D017262:Siderophores; D006856:Hydrogen Cyanide; D011764:Pyrrolnitrin