Multi-omics characterization of the osmotic stress resistance and protease activities of the halophilic bacteriumPseudoalteromonas phenolicain response to salt stress

Abstract

The halophilic bacteriumPseudoalteromonas phenolicais well known as a promising candidate that enables the recycling of organic wastes at high salinity. However, for industrial applications ofP. phenolicafurther research is required to explore the biological mechanism for maximizing the activities and productivities of this bacterium. In this study, we investigated the osmotic stress resistance and specific protease activities ofP. phenolicain a normal-salt medium (0.3 M NaCl) and high-salt medium (1 M NaCl) based on intra- and extracellular multi-omics approaches. Proteins related to betaine and proline biosynthesis were increased under high salt stress. The targeted metabolite analysis found that proline was overproduced and accumulated outside the cell at high salinity, and betaine was accumulated in the cell by activation of biosynthesis as well as uptake. In addition, extracellular serine proteases were shown to be upregulated in response to salt stress by the extracellular proteomic analysis. The specific proteolytic activity assay indicated that the activities of serine proteases, useful enzymes for the recycling of organic wastes, were increased remarkably under high salt stress. Our results suggest that betaine and proline are key osmoprotectant metabolites ofP. phenolica, and they can be used for the improvement of protease production andP. phenolicaactivities for the recycling of high-salt organic wastes in the future.