Morphological and Molecular Characterization of Lactic acid Bacteria from intestine of Freshwater Fishes and Their Possible Role in Probiotic Feeding in Aquaculture

Abstract

Lactic acid bacteria (LAB) are a group of gram positive, non spore forming, cocci or rod shaped, catalase negative organisms. Generally they are known as "GRAS" (Generally Recognized As Safe) organisms. In the present study, an attempt was made to isolate lactic acid bacteria from gut of two freshwa-ter fishes in Udaipur region to obtain various efficient LAB strains for indus-trial applications. A total of 12 bacterial isolates were isolated from different fishes caught from Pichola lake, Udaipur on MRS agar at 37oC. All the isolates were tested for catalase activity, colony morphology and gram staining. Further these isolates were checked for technological properties (antibacterial activity, antibiotic susceptibility and bile salt tolerance). Based on technologi-cal properties results, two isolate (F-4 & F-11) have been tentatively selected for use as probiotic cultures in the aquaculture industries. They have strong antibacterial activity against various pathogens viz. Staphylococcus aureus (ATCC 9144), Micrococcus luteus (ATCC 10240), Listeria monocytogens (MTCC 1143) and have bile salt tolerance limit up to 0.7%. These are the main features for selection of probiotic candidates. To differentiate the same species molecular typing was attempted, 16S rRNA gene amplification was done using specific 16S rDNA primers and amplified gene products were di-gested with different restriction endonuclease enzymes viz EcoRI and HindIII. A total of 2 different groups out of 12 isolates were obtained. This finding reveals that isolated LAB are useful for aquaculture and also used in food preservation.