~ 199 ~ International Journal of Fisheries and Aquatic Studies 2014; 1(6): 199-207 ISSN: 2347-5129 IJFAS 2014; 1(6): 199-207 © 2013 IJFAS www.fisheriesjournal.com Received: 07-05-2014 Accepted: 02-06-2014 Janakiram P. Assistant professor Department of Marine Living Resources, Andhra University, Visakhapatnam - 530 003, (A P) India. Veerendra kumar M. Research scholar Department of Marine Living Resources, Andhra University, Visakhapatnam - 530 003, (AP) India. Jayasree L. Senior scientist Central Marine Fisheries Research Institute, Karwar - 581301, Karnataka, India. Sivaprasad B. Research Scholar Department of Marine Living Resources, Andhra University, Visakhapatnam - 530 003, (A P) India. Correspondence: Janakiram P. Assistant professor Department of Marine Living Resources, Andhra University, Visakhapatnam - 530 003, (A P) India. Probiotic activity of Pseudomonas aeruginosa (PIC-4) isolated from Visakhapatnam coast, Bay of Bengal, India, against Vibrio harveyi in Penaeus monodon Janakiram P., Veerendra kumar M., Jayasree L., Sivaprasad B. Abstract Pseudomonas aeruginosa (PIC 4), isolated from coastal waters of Visakhapatnam (Gen Bank Accession no: KF803248) was tested for its antagonistic activity against Vibrio harveyi as probiotic in cultured Penaeus monodon. Pseudomonas aeruginosa PIC 4 has proved to be non-pathogenic to the shrimp by pathogenicity tests. Vibrio counts in probiotic fed shrimp and the surrounding water medium were significantly lower when compared to the control group of shrimp and water during 50 days of culture. Mean weight of probiont fed shrimps after 50 days of culture was (2.21 + 0.15 g) , significantly higher than that of normal diet fed ones (1.33+0.18 g). Survival percent was also significantly higher in probiont fed shrimp (47.33% + 5.55%) than that of the control diet fed shrimp (26.33% + 7%). Percent survival in probiotic fed and normal diet fed shrimp after the challenge with V. harveyi was 93.04 and 38.87 respectively. Keywords: Probiotc, Pseudomonas aeruginosa, Vibrio harveyi, Penaeus monodon. 1. Introduction The pathogenic Vibrio spp. have been implicated as major cause of bacterial infections in shrimp aquaculture [1] . Vibrio harveyi, a luminous species and commonly isolated from marine source, has been recognized to be pathogenic for fish and several Crustaceans, particularly, Penaeus spp. [2, 3, 4] . As antibiotic resistant strains are becoming more prevalent and difficult to treat, alternative methods of controlling the microbial environment are gaining significance [5] . Several alternative strategies to the use of antimicrobials in disease control have been proposed and applied very successfully in aquaculture [6] . A number of preventive approaches such as the use of vaccines, immunostimulants, and probiotics have been explored in order to reduce the losses due to diseases and mortality of cultured stock. A successful alternative method to antibiotic treatment is the application of probiotics. Probiotics have been proved to enhance specific, non-specific immunity and also improve water quality [7, 8, 9] . A variety of microbes have been investigated for use as probiotics in aquaculture such as Gram positive, Gram negative bacteria, yeast and unicellular algae [10, 11] . Pseudomonas aeruginosa isolated from Visakhapatnam coast was used as an alternative to the existing probiotic bacteria to fight against the V. harveyi infections in the cultured shrimp P. monodon. 2. Materials and Methods: 2.1 Selection of isolate & testing of antagonistic activity Pseudomonas aeruginosa (PIC 4) isolated from Visakhapatnam coast (NCBI GenBank Accession no: KF803248) has been selected to test as probiotic bacterium against V. harveyi (MTCC 3438) in cultured shrimp (Penaeus monodon). Antagonistic activity of the isolate PIC 4 was tested by cross streak and agar well diffusion methods [12] . 2.2 Pathogenicity Experiment Pathogenicity of Pseudomonas aeruginosa (PI C4) was tested on the postlarvae (PL) of Penaeus monodon (stage PL15) obtained from a commercial hatchery. The postlarvae tested negative for white spot syndrome virus (WSSV) by nested PCR (WSSV Detection Kit supplied by Genei Bangalore, India) were acclimatised in laboratory for two days before conducting the experiment. One hundred Postlarvae (PL 15) of P. monodon were placed in each plastic tub of 8