ISOLATION AND CHARACTERIZATION OF PLANT GROWTH-PROMOTING BACTERIA FROM DIFFERENT RHIZOSPHERIC SOILS

Abstract

The production of indole acetic acid (IAA) is a significant property of rhizospheric bacteria to stimulate and promote plant growth. In this investigation, indole acetic acid-producing bacteria from the rhizosphere of five distinct plants (Wheat, Gulchen, Rose, Lady Finger, and Bouginvella) were isolated and characterized. Bacterial strains were isolated and identified by morphological characterization. Out of 30 bacterial isolates, 5 isolates were selected as efficient producers of Indole acetic acid. These selected bacterial isolates were subjected to several biochemical tests for identification at the genus level. After the determination of bacterial genus, antibiotic sensitivity test was performed to check the resistance pattern of each bacterial isolate against antibiotics. Selected bacterial isolates were characterized by using molecular techniques. DNA of five bacterial isolates was extracted by WizPrepTMg DNA mini kit and amplification of 16S rRNA gene was done by PCR. Amplification of PCR product was confirmed by agarose gel electrophoresis. From biochemical tests, Klebsiella spp., E. coli, and Bacillus sp. tested positive. Klebsiella spp. showed 87, 88, 81, 88, 91, 100, 90, and 87% resistance against enrofloxacin, gentamycin, penicillin, ampicillin, chlotetracyclin, tylosine, oxytetracycline, and amoxicillin, respectively. E. coli showed 80, 88, 79, 84, 79, 86, 82, and 89% against enrofloxacin, gentamycin, penicillin, ampicillin, chlotetracyclin, tylosine, oxytetracycline, and amoxicillin respectively whereas 87, 91, 100, 100, 93, 100, 89 and 100% resistance was shown by Bacillus sp. against enrofloxacin, gentamycin, penicillin, ampicillin, chlotetracyclin, tylosine, oxytetracycline, and amoxicillin, respectively. All these selected bacterial isolates were found positive for the 16S rRNA gene and characterized as Klebsiella pneumonia RY6, Klebsiella oxytoca strain RY8, Klebsiella oxytoca RY10, Escherichia coli RY20, and Bacillus tequilensis RY23. It is concluded that the property of synthesizing IAA is considered an effective tool for the isolation and characterization of bacteria that have a role in promoting plant growth.