Evaluation of antimicrobial substance produced by a bacterium isolated from Parmacella iberica

Introduction and objective: Nowadays, widespread application of antibiotics results in resistant microorganisms all over the world. Thus screening researches for the products with antimicrobial activity have been lead to probe natural sources of antimicrobial agents to find new pharmaceutical products. Here we describe the antagonistic activity of a bacterium isolated from digestive system of Iran endemic slug, Parmacella iberica, its biochemical identification and phylogenetic relationships and extraction of antimicrobial substance.

Materials and methods: Samples from digestive system of slugs were immediately transferred to broth medium. Antimicrobial agent-producing bacteria were isolated using serial dilution method on nutrient agar. One of them was selected for more investigation. Disk diffusion test was used against some laboratory standard strains to screen the antimicrobial potential. Identification of bacteria was done with 16S ribosomal DNA amplification and standard biochemical tests.

Results: Phylogenetic analysis of 16S rDNA gene of this bacterium showed similarity to Pseudomonas aeruginosa confirmed by the result of biochemical tests. The results of the antibiogram assay implied that the antimicrobial substance is broad-spectrum. This substance is nonpolar since it is extracted by different solvents. The cell growth measurements revealed that this compound was produced at first logarithmic phase.

Conclusion: High antimicrobial effects of the bacterium are evident. Due to increscent need to new antibiotics, purification and identification of this antimicrobial compound seem to be necessary for introducing new medicinal source.

Significance and impact of the study: The isolation of bacterial strain producing antimicrobial agent with the broad spectrum antimicrobial properties is proposed.