Algae-lysing activity of Vibrio mediterranei 117-T6

Many algal pathogens have a broad spectrum of algae-lysing activity. In order to verify whether Vibrio mediterranei 117-T6 (Vm 117-T6) has broad-spectrum algicide properties, this paper observed its algal lysis on Heterosigma akashiwo, Pleurochrysis carterae, Dirateria inornata and Prorocentrum donghaiense, and the characteristics of the algae-lysing substances were analyzed. In this study, Vm 117-T6, a pathogenic bacterium for the yellow spot disease of Pyropia, showed a broad-spectrum algae-lysing activity. It exhibited strong algae-lysing activity to H. akashiwo, P. carterae, D. inornata and P. donghaiense, which significantly reduces the chlorophyll content of these microalgaes. Vm 117-T6 can also reduce the motility of H. akashiwo within 40 min, inhibit photosynthesis, cause algal lysis and produce white flocculent precipitates after infection over the 120 min. Vm 117-T6 can degrade carrageenan, but cannot degrade pectin, cellulose and chitin. The live bacterium, its intracellular and extracellular extracts showed strong microalgae-lysing activity. The extracellular algae-lysing compounds were easily soluble in water, insoluble in petroleum ether and ethyl acetate, which indicated strong polarity. It was resistant to high temperature, and was not easy adsorbed by activated carbon. Ethanol treatment reduced the lysing-algae activity. There were a large amount of ABC transporter, outer membrane protein, flagellin and a small amount of toxin in the key differential proteins under conventional and susceptible conditions. The results indicate that Vm 117-T6 does not dissolve algae through cell wall degradation, and the virulence effectors of Vm 117-T6 contain endotoxins, and the proteins related to the transport, secretion and cell adhesion may play an important role in the virulence of Vm 117-T6. This paper provides evidence for the analysis of the algae-lysing mechanism of this strain, and also lays a foundation for the prevention and control of this strain.