Inhibitory activity against the fish pathogen Lactococcus garvieae produced by Lactococcus lactis TW34, a lactic acid ba
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ORIGINAL PAPER
Inhibitory activity against the Wsh pathogen Lactococcus garvieae produced by Lactococcus lactis TW34, a lactic acid bacterium isolated from the intestinal tract of a Patagonian Wsh Cynthia Sequeiros · Marisol Vallejo · Emilio Rogelio Marguet · Nelda Lila Olivera
Received: 8 September 2009 / Revised: 4 January 2010 / Accepted: 20 January 2010 / Published online: 6 February 2010 © Springer-Verlag 2010
Abstract After enrichment of Odontesthes platensis intestinal contents, 53 lactic acid bacteria (LAB) were isolated. From the four isolates that showed inhibitory activity against Lactococcus garvieae 03/8460, strain TW34 was selected because it exerted the strongest inhibition. It also inhibited other Gram-positive bacteria, but not Gram-negative Wsh pathogens. Phenotypic and 16S rDNA phylogenetic analyses showed that TW34 belongs to Lactococcus lactis. In addition, TW34 showed to be sensitive to diVerent antibiotics. The production of the inhibitory agent against L. garvieae was growth associated, and it was signiWcantly inXuenced by the incubation temperature. The optimal temperature for the antimicrobial production was as low as 15°C. Both acidiWcation and hydrogen peroxide production were ruled out as the source of inhibition. In contrast, the antimicrobial activity was completely lost by treatment with proteolytic enzymes, which conWrmed that the inhibitory substance was a bacteriocin. The bacteriocin was highly thermostable (121°C for 15 min) and active between pH 3 and 11. It remained stable for up to 2 months when stored at 4°C and up to 6 months at ¡20°C. Our results suggest that the strain L. lactis TW34 could provide an
Communicated by Erko Stackebrandt. C. Sequeiros (&) · N. L. Olivera Centro Nacional Patagónico (CENPAT-CONICET), Blvd. Brown 2915, U9120ACD Puerto Madryn, Chubut, Argentina e-mail: [email protected] M. Vallejo · E. R. Marguet Cátedra de Biología Celular y Molecular, Facultad de Ciencias Naturales (FCN) Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), Sede Trelew. Roca 115, 1º Piso (9100), Trelew, Chubut, Argentina
alternative for lactococcosis control and therefore be considered for future challenge experiments with Wsh. Keywords Lactic acid bacteria · Lactoccocus lactis · Bacteriocin · Antimicrobial peptide · Lactococcus garvieae · Fish pathogen
Introduction Lactococcosis is an emerging disease caused by Lactococcus garvieae, which aVects many Wsh species such as rainbow trout, yellowtail, tilapia, and catWsh, in both marine and freshwater aquaculture (Vendrell et al. 2006). This illness produces a hyperacute and hemorrhagic septicemia, which evolves depending on the environmental conditions of the Wsh habitat with temperature and the microbiological quality of the water being especially important (Vendrell et al. 2006). Two traditional strategies used to Wght against bacterial diseases in farmed Wsh are vaccination and antibiotic treatment; however, both methods have drawbacks. Commercial vaccines are available for some pathogens (Gomes et al. 2006), bu
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