Research Journal of Recent Sciences _________________________________________________ ISSN 2277-2502 Vol. 4(ISC-2014), 170-172 (2015) Res. J. Recent. Sci. International Science Congress Association 170 Antagonistic effect of Lactobacilli of Camel Milk against Aeromonas veronii isolated from Pichola lake, Udaipur, Rajasthan, India Khandelwal D., Joshi H.*andChaudhary B.L. Department of Biotechnology, Mohanlal Sukhadia University, Udaipur-313001, Rajasthan, INDIAAvailable online at: www.isca.in, www.isca.me Received 25th Novmeber 2014, revised 23rd January 2015, accepted 17th February 2015 AbstractWater microbiology is concerned with the microorganisms that live in water. Water may possess many pathogenic bacteria, viruses, protozoa and parasites. They are responsible for the emerging most widespread infections which are leading cause of death worldwide. Aeromonas veronii is commonly found in freshwater systems. Aeromonas is gram negative, facultative anaerobic bacteria. It causes aeromonasis in humans and is also pathogenic for aquatic and terrestrial animals . Pichola lake is one of the most beautiful lake of Rajasthan, India. It is an important source of potable water supply for the city . In the present study, an attempt has been made to isolate the lactobacilli from camel milk and detect the antibacterial activity of lactobacilli against previously isolated and identified Aeromonas veronii from lake Pichola. A total of 10 lactobacilli were isolated and subjected to agar well assay for detection of antibacterial activity. Out of them, 2 isolates showed demonstrable antibacterial activity against Aeromonas veronii. On the basis of biochemical and molecular characteristics these two isolates were identified as Lactobacillus rhamnosus CMU 14 and Lactobacillus fermentum CMU 17. Further investigation may reveal that these lactobacilli isolates could be used as potential probiotics for aquaculture and to manage aeromonasis. Keywords: Aeromonas veronii, Pichola lake, lactobacilli, antibacterial activity. Introduction Water is the vital source of our planet. The consumable water levels are up to 2.7% of the total water content reported by United nations (UN) in 1978. Water quality now is a concern for all countries in the world. Microbial contamination is the most important factor of water pollution especially with pathogenic organisms. The pathogenic organisms includes various types of bacteria, viruses and protozoans. They cause infection in humans as well as in aquatic animals. Aeromonas are commonly isolated from a variety of aquatic environments, including freshwater, estuarine, brackish, and salt waters. Aeromonas veronii is gram- negative, facultative anaerobic bacterium which causes disease in humans as well as aquatic animals Lake Pichola, situated in Udaipur city is an artificial fresh water lake. It is polluted due to the disposal of sewage directly into the lake water. “Probiotics” defined as “mono or mixed cultures of live microorganisms which, when applied to animal, beneficially affect the host by improving the properties of the indigenous microflora”. The term “Probiotic” refers to gram-positive bacteria associated with the genus Lactobacillus. One of the requirements needed for probiotic strains is that they should possess antibacterial activity against various pathogenic organisms. According to Yasuda and Taga5, LAB would be useful both as food and as biological control agents of disease and activators of the rate of nutrient regeneration in aquaculture. Hence the present work was carried out to screen the antibacterial activity of lactobacilli isolated from camel milk against water borne pathogen Aeromonas veronii.Material and MethodsIsolation and morphological characterization of lactobacilli: For isolation of lactobacilli, serial dilution technique was used. Serial dilution was done using the saline solution. Serially diluted samples were pour plated with the MRS medium. Isolated colonies were recovered from the plates after an incubation period of 48 h at 37C. The individual colonies were selected and transferred into sterile MRS broth medium and were further purified by successive streaking. Selected colonies were screened on the basis of gram reaction, morphology and catalase test. Screening of lactobacilli for antibacterial activity: For screening of antibacterial activity against Aeromonas veronii, lactobacilli were inoculated to MRS broth and incubated at 37C for 24-48 h. The stationary cells were centrifuged at 3000 rpm for 20 min. The culture supernatant neutralized with and without 1N NaOH was tested for antibacterial activity by the agar well diffusion assay as described by Schillinger and Luke. Biochemical characterization of lactobacilli isolates: Biochemical identification was based on the phenotypic properties such as CO production from glucose, hydrolysis of arginine, growth at different temperatures (15 and 45C). Fermentation of carbohydrate was determined using CHL medium (a basal media used for sugar fermentation test).