en Biotechnology Biotechnology پژوهشي Orginal research papers <font face="Times New Roman" size="3"> </font><p class="MsoNormal" style="margin: 0cm 0cm 0pt text-align: justify line-height: 120%"><font face="Times New Roman"><font size="1">Probiotic is considered as a remedy to solve disease problem in shrimp aquaculture. Shrimp body and environment bacterial flora are recommended as reliable source for extracting of beneficial bacteria. Therefore, 5000 pieces of post larvae of <i>Penaeus monodon</i> were distributed equally in 4 tanks in probiotic and antibiotic free condition up to juvenile. Then microbiological samples from digestive system, muscles, body surface, rearing water and tank sediment were inoculated onto the selective media plates. Incident of total bacteria, <i>Vibrio</i>, <i>Pseudomonas</i> and <i>Entrobacteriaceae</i> were evaluated in different body parts and rearing environment of shrimp. The highest bacteria count for total bacteria, <i>Vibrio</i>, <i>Pseudomonas </i>was occurred in sediment followed by digestive system. No <i>Entrobacteriaceae</i> was observed from all samples. Isolated bacteria were identified and placed in 7 genera consisted of <i>Vibrio</i>, <i>Shewanella</i><b>, </b><i>Burkholderia</i><b>, </b><i>Clavibacter</i><b>, </b><i>Staphylococcus</i><b>, </b><i>Brevibacterium</i><b>, </b><i>Corynebacterium</i>, while one genus remained unidentified. Genus <i>Shewanella</i> exhibited highest frequent bacteria in digestive system of <i>P. monodon </i>which may be indicated its ability to colonization in digestive system. <i>Shewanella algae</i> was selected from whole isolated bacteria as candidate probiotic via well plate diffusion technique and cross streak antagonistic test against <i>Vibrio harveyi</i>, <i>V. parahaemolyticus</i> and <i>V. alginolyticus</i>. It was able to digest lipid and protein in tributyrin agar and skim milk agar.<span style="mso-spacerun: yes"> </span></font></font></p><font face="Times New Roman" size="3"> </font> Probiotic, Shewanella algae, Penaeus monodon, Shrimp 849 866 http://jifro.ir/browse.php?a_code=A-10-1-204&slc_lang=en&sid=1 S. Shakibazadeh 10031947532846004754 10031947532846004754 No S. Che Roos cheroos@agri.upm.edu.my 10031947532846004755 10031947532846004755 Yes M. Hafezieh 10031947532846004756 10031947532846004756 No A. Christianus 10031947532846004757 10031947532846004757 No M. Saleh Kamarudin 10031947532846004758 10031947532846004758 No Sijam Kamaruzaman 10031947532846004759 10031947532846004759 No