Screening, isolation, and antibacterial activity of antibiotic producing bacteria obtained from saprophytic soil samples

Abstract

Objective: The aim of the study was conducted to screen and isolate potential antibiotic producing bacteria from saprophytic soils collected from Potheri and Nandiambakkam. Methods: Soil was collected aseptically and subjected to serial dilution. Crowded plate technique was used for the isolation of the colony. Totally seven isolates were isolated and were screened for their antibacterial activity. The three isolates (S2A, S2B, and S3A) having better zone of inhibition were selected for morphological, microscopical, and biochemical test to prove their validity. The selected isolates were partially purified. The partially purified samples further screened for antibacterial activity, minimum inhibitory concentration (MIC) and the isolates, which shown good zone of inhibition were subjected to 16S rRNA sequencing studies to determine the species. Results: The isolates screened based on size of the zone formed. Best isolate selected by zone of inhibition was subjected to antibacterial activity, morphological, microscopical, and biochemical test, partial purification of three isolates and further screened for antibacterial and MIC. The isolate showed good zone of inhibition compared to others by MIC was selected for 16S rRNA sequencing studies. Genomic DNA extracted from isolate S2B conforms it belongs to Pseudomonas species which is named as Pseudomonas putida 2435. Conclusion: The research work revealed that the three isolates showed good antibacterial activity against Gram-positive and Gram-negative bacteria. The S2B isolate was confirmed to P. putida 2435 by 16S rRNA studies.