Efecto inhibitorio de la microalga Isochrysis galbana (Haptophyta) sobre bacterias tipo Vibrio spp.

Abstract

La capacidad inhibitoria de la microalgaIsochrysis galbana fue evaluada sobre Vibrio furnisii (reportado como patógeno en acuicultura). Se efectuaron cultivos monoespecíficos, por triplicado, en medio “f2” a una densidad inicial de 1×105células/ml, inoculándose cada cultivo con >1×102 bacterias que crecen en medio TCBS (BTCBS). Se efectuaron conteos diarios de la microalga y se determinó su tasa de crecimiento. El efecto inhibitorio se evaluó mediante filtrados de 1 y 10 ml del cultivo microalga-bacteria, inmediatamente después de la inoculación, a las 48, 96, 168 horas, y una vez que el cultivo de microalga alcanzara la fase estacionaria de su crecimiento, se efectuaron conteos indirectos de BTCBS. En todas las repeticiones se detectaron diferencias significativas (α=0.05) de la concentración de Vibrio con respecto al tiempo, hallándose concentraciones indetectables (<0.01BTCBS/ml) durante la fase exponencial del crecimiento de la microalga. I. galbana, presenta un mayor crecimiento y densidad celular en presencia de Vibrio furnisii (α=0.05) demostrando la propiedad alelopática entre ambas especies. Se efectuó un análisis por HPLC de extractos microalgales (0.1gr de pellet), usando n-butanol y metanol como solventes, se registra mayor presencia de compuestos extracelulares con metanol. Se usaron extractos microalgales con n-butanol y metanol (0.1 y 0.5gr de pellet) para el test de sensibilidad, registrándose halos de inhibición más grandes con metanol (0.5gr de pellet). Se concluye la efectividad y selectividad de Isochrysis galbana sobre Vibrio furnisii, debido a los metabolitos secundarios que ésta libera, demostrando su uso como agente potencial de biocontrol sobre vibriosis.

The inhibitory capacity of Isochrysisgalbana was evaluated against Vibrio furnisii (reported as a pathogen in aquaculture). The microalgae was maintained in monospecific cultures (by triplicate), in “f2” media at an initial density of 1×105células/ml, each culture was inoculated with Vibrio furnisii with a density >1×102 (bacteria is able to grow up in TCBS media, BTCBS). Daily counts of microalgae culture were done to calculate growth rate. The inhibitory effect was evaluated trough filtering (1 y 10ml) samples of microalgae-bacteria culture, immediately after the inoculation, at 48, 96, 168 hours and at the time that microalgae were at stationary growth phase, trough indirect counts of BTCBS. In all experiments, highly significant differences in the concentration of Vibrio over time were found, and undetectable (<0.01BTCBS/ml) concentration were detected when microalgae culture were at the exponential growth phase. I. galbana showed high growth and cellular density when it was cultured with V. furnisii (α=0.05), showing the allelopathic property between them. It was done an HPLC analysis with microalgae extracts (0.1gr pellet), using n-butanol and methanol as solvents; it was found that methanol extracts more extracellular compounds than n-butanol. Microalgae extracts with n-butanol and methanol (0.1y0.5gr) were used to make sensibility tests, metanol (pellet 0.5gr) showed big inhibition halos. We conclude the effectivity and selectivity of I. galbana against V. furnisii, due to the secondary metabolites of microalgae, showing its capacity to be a potential agent of biocontrol against vibriosis.