Relative abundance and species composition of gram-negative, aerobic bacteria associated with the gut of juvenile white shrimp Litopenaeus vannamei reared in oligotrophic well water and eutrophic pond water

Gut bacteria may contribute significantly to the growth and survival of cul tured shrimp, although little is known about factors that affect bacterial community structure in shrimp guts. The objective of this study was to dete rmine the abundance and species composition of gut bacteria in juvenile whi te shrimp Litopenaeus vannamei reared in two different environments. Eight 120-L tanks were stocked at a density of 8 shrimp/tank. Two treatments were tested for 10 d and consisted of tanks receiving flow-through water from o ne of two sources: 1) well water pumped from a seawater aquifer (Well treat ment), and 2) pond water pumped from an intensive shrimp pond (Pond treatme nt). Shrimp mid- and hindguts were excised on days 1, 3, 6, and 10 for enum eration of gram-negative, aerobic bacteria by quantifying colony-forming un its (CFU) using standard microbiological plating techniques. identification of bacterial isolates was made using the Biolog(R) GN MicroPlate system. B acterial numbers were significantly greater (P < 0.05) in Well shrimp than in Pond shrimp on days 1 and 3. Following day 3, a decrease in bacterial nu mbers occurred in the Well shrimp, and no significant differences between t reatments were observed on days 6 or 10. Guts from Well shrimp were dominat ed by Vibrio and Aeromonas, and these two genera accounted for 80-85% of th e bacteria on each sampling day. Guts from Pond shrimp exhibited a greater bacterial diversity and were dominated by Vibrio, Aeromonas, and Pseudomona s. Flavobacterium were identified in the guts of Pond shrimp on days 3 and 10, but were not identified in any of the Well shrimp. A greater understand ing of gut bacteria-shrimp interactions could lead to increased production and profitability for shrimp farmers through the development of more cost-e ffective feeds and novel disease control strategies.