Potential role of alginate in marine bacteria-yeast interactions

The ability of microorganisms to decompose brown algae has attracted attention. This study aims to clarify the characteristics of marine microbial communities in which prokaryotic and eukaryotic microorganisms interact via the metabolism of brown algae carbohydrates. Amplicon-based microbiome analysis revealed the predominance of the genera <i>Marinomonas</i> and <i>Vibrio</i> in seawater and seaweed samples mixed with alginate and mannitol, which are the primary carbohydrates in brown algae. Three <i>Vibrio</i> species and <i>Candida intermedia</i> were isolated via alginate enrichment culture. Although <i>C. intermedia</i> did not utilize alginate as a nutrient source, the yeast grew in the spent alginate medium in which <i>Vibrio algivorus</i> had been cultured. Coculture with <i>C. intermedia</i> and the <i>Vibrio</i> isolates, especially <i>V. algivorus</i>, also enhanced the growth of the yeast on alginate. These results suggested that <i>C. intermedia</i> grew because of the supply of nutrients via alginate metabolism by <i>Vibrio</i> species. In the coculture medium, the amount of phosphatidylserine increased in the early phase but decreased with the growth of <i>C. intermedia</i>, indicating that phosphatidylserine secreted by <i>Vibrio</i> is involved in the putative mutualistic interaction. We examined whether such interaction is applicable to the production of useful substances and succeeded in lipid production by oleaginous marine yeast <i>Yarrowia lipolytica</i> through coculture with <i>V. algivorus</i>. Our study suggested the potential of mutualistic interaction via degradation of alginate by marine <i>Vibrio</i> for production of industrially useful substances in yeast cells.IMPORTANCEIn this study, we analyzed the microbiome of seawater and seaweed in the presence of brown algae carbohydrates and reconstructed the putative mutualistic relationship of marine <i>Vibrio</i> and <i>Candida intermedia</i> mediated by metabolism of brown algae in the ocean.