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A Molecular Insight of Some Probiotic Bacteria to Address Their Antagonistic Activity Against Pathogenic Vibrios Causing Shrimp Mortality

Tasmia Farzana
Department of Microbiology, University of Dhaka, Dhaka 1000, Bangladesh.

Shafiqur Rahman
Department of Microbiology, University of Dhaka, Dhaka 1000, Bangladesh.

M. Niamul Naser
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh.

Muhammad Manjurul Karim
Department of Microbiology, University of Dhaka, Dhaka 1000, Bangladesh.

Abstract/ Executive Summary:

The molecular basis of antagonistic activity of a number of probiotic bacteria was analyzed using plasmid curing method. Earlier, six bacteria having potential probiotic activity under laboratory conditions were screened from 96 isolates which were obtained from shrimp rearing environment from south-west coastal region of Bangladesh. Among the isolated probionts, five were subjected to plasmid curing method and three were found to harbor plasmids, as was revealed in an agarose gel electrophoresis. Curing of these plasmids demonstrated that the bacteria lost its antagonistic activity, indicating the activity could be plasmid-borne. The antagonistic activities of the rest two isolates however, were not plasmid-oriented as no plasmid was recovered from them.

Keywords: Probiotic bacteria, Antibiotic, Vibrios, Plasmid

Location: Department of Microbiology, University of Dhaka, Dhaka 1000, Bangladesh.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Shrimp

Objectives:

To isolated using different culture media by observing zone of inhibition against pathogenic vibrios.

Methodology:

This study was conducted with five putative probiotic bacteria, hereafter designated as, ‘A’ (for SCT10P2), ‘B’ (for SCS192N), ‘D’ (for SCT012C), ‘E’ (for SCT015C) and ‘F’ (for SCT013C). These bacteria were isolated using different culture media by observing zone of inhibition against pathogenic vibrios. The probiotic potential was initially examined in agar diffusion assay, and the observation was finalized with the concatenation of screening including characterization, ensuring mammalian safety, and cytotoxicity test; and presumptive identification by microscopic observation and biochemical properties. In this study, these five isolates were examined for presence of plasmid, followed by their curing (removal) if present, in order to correlate their involvement in bringing about antagonistic activity against the pathogenic organisms. Plasmid extraction was accomplished using pure link Quick plasmid Miniprep kit following the manufacturer’s instruction. Extracted plasmids were visualized by electrophoresis on a 0.5% agarose gel followed by staining with ethidium bromide (Et-Br). Distinct bands for plasmids, having >10 kb sizes were observed in gel, but only for isolates ‘B’, ‘D’, and ‘E’; while ‘A’ and ‘F’ did not produce the same.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 115-120, 2013, ISSN 0378-8121

Article Link (Online Journal): DOI: http://dx.doi.org/10.3329/jbas.v37i1.15688

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From experience, it was revealed that the environmental strains tend to shed their acquired potential, e.g. probiotic activity, upon prolonged storage in laboratory conditions. Hence, the long-term effectiveness of a probiotic isolate from the natural environment remains a tricky question. If the plasmids contributing probiotic potential could be isolated, and their effectiveness could be verified upon transformation into competent cells of laboratory strains, a smart approach would be to construct a plasmid bank conferring probiotic activity against a selective group of organisms. This will enable to prepare bacterial cells upon transformed with the plasmid conferring probiotic potential, and hence could be delivered in sites in need at any given time. The current concern is to build up such a plasmid bank, collected from environmentally isolated probiotic strains that could be readily dispensable upon requirement.

Knowledge Management: Journal