www.pelagiaresearchlibrary.com t Available online a Pelagia Research Library European Journal of Experimental Biology, 2013, 3(3):236-240 ISSN: 2248 –9215 CODEN (USA): EJEBAU 236 Pelagia Research Library Isolation and screening of gut microflora from Siganus guttatus (Bloch, 1787) for potential anti-vibrio agents Victor Marco Emmanuel N. Ferriols * , Marciel G. Siladan, Allan N. Failaman and Rex Ferdinand M. Traifalgar Institute of Aquaculture – College of Fisheries and Ocean Sciences, University of the Philippines Visayas, Miagao, Iloilo, Philippines _____________________________________________________________________________________________ ABSTRACT Bacteria from the gastrointestinal tract of the rabbitfish Siganus guttatus (Bloch, 1787) were isolated and screened for their potential as anti-vibrio agents. A total of four isolates based on colony dominance and morphology were selected and tested against Vibrio harveyi in cross-streak and co-culture tests. Although no inhibition was observed for all isolates in the cross-streak tests, a significant reduction was observed in the population of V. harveyi in co- culture with all isolates. Reduction in V. harveyi population ranging from 63.9% - 100% were observed within 24 hours of inoculation. This study showed the potential of bacteria isolated from the gut of S. guttatus to act as a possible control agents against V. harveyi especially in cultures of shrimps and prawns wherein S. guttatus could be raised in tandem to produce “green water”. Keywords: Siganus guttatus, gut microflora, anti-vibrio _____________________________________________________________________________________________ INTRODUCTION In recent years, the use of “green water” technology as a biocontrol measure to prevent Luminous Vibriosis in shrimp farms has gained much acceptance [3]. This technology has been the subject of many studies ranging from refining protocols in achieving “green water” to elucidating the many factors involved in preventing the outbreak of Luminous Vibriosis. Although this technology initially focused on the use of Tilapia to produce the desired green water, studies have shown that other fish species such as milkfish, rabbitfish, and seabass produced similar results [12]. Most of these studies have pointed to the role of fish mucus and the various microalgal species present in the green water in inhibiting the growth of Vibrio species in culture systems [8]. The role of other bacterial species present in green water in the inhibition of Vibrio species has also been proposed through the concept of competitive exclusion. The presence of Vibrio-inhibiting bacteria has been associated with green water technology although the possible sources of such bacteria have not been elucidated thoroughly in previous studies. One potential source of such vibrio-inhibiting bacteria is the gastrointestinal tract of the fish used in green water technology. Lactic acid bacteria