Abstract

Shewanella sp. HM13 is a cold-adapted Gram-negative bacterium isolated from the intestine of a horse mackerel. It produces a large amount of outer membrane vesicles (OMVs), which are particles released in the medium where the bacterium is cultured. This strain biosynthesizes a single major cargo protein in the OMVs, a fact that makes Shewanella sp. HM13 a good candidate for the production of extracellular recombinant proteins. Therefore, the structural characterization of the components of the vesicles, such as lipopolysaccharides, takes on a fundamental role for understanding the mechanism of biogenesis of the OMVs and their applications. The aim of this study was to investigate the structure of the oligosaccharide (OS) isolated from Shewanella sp. HM13 cells as the first step for a comparison with that from the vesicles. The lipooligosaccharide (LOS) was isolated from dry cells, purified, and hydrolyzed by alkaline treatment. The obtained OS was analyzed completely, and the composition of fatty acids was obtained by chemical methods. In particular, the OS was investigated in detail by 1H and 13C NMR spectroscopy and MALDI-TOF mass spectrometry. The oligosaccharide was characterized by the presence of a residue of 8-amino-3,8-dideoxy-manno-oct-2-ulosonic acid (Kdo8N) and of a d,d-heptose, with both residues being identified in other oligosaccharides from Shewanella species.

Highlights

  • Cold-adapted bacteria are extremophiles that are able to thrive in permanently cold environments.Some of these habitats are exposed to temperatures below 5 ◦ C [1], and for this reason cold-adapted microorganisms have developed unique physiological tools to survive in these harsh conditions.Cold habitats are considered as surprising reservoirs of biotechnological molecules such as antibiofilm molecules [2], surfactants [3], cold-active enzymes [4], antifreeze proteins, glycoproteins, and polysaccharides [5,6,7]

  • The oligosaccharide was characterized by the presence of a residue of 8-amino-3,8-dideoxy-manno-oct-2-ulosonic acid (Kdo8N) and of a D,D-heptose, with both residues being identified in other oligosaccharides from Shewanella species

  • It has been reported that the outer membrane vesicles (OMVs) produced by a cold-adapted bacterium contain putative proteolytic enzymes, which can serve to degrade high molecular weight molecules present in the surrounding cells [9,10] helping the bacterium in the survival of such harsh conditions

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Summary

Introduction

Cold-adapted bacteria are extremophiles that are able to thrive in permanently cold environments.Some of these habitats are exposed to temperatures below 5 ◦ C [1], and for this reason cold-adapted microorganisms have developed unique physiological tools to survive in these harsh conditions.Cold habitats are considered as surprising reservoirs of biotechnological molecules such as antibiofilm molecules [2], surfactants [3], cold-active enzymes [4], antifreeze proteins, glycoproteins, and polysaccharides [5,6,7]. Cold-adapted bacteria are extremophiles that are able to thrive in permanently cold environments. Some of these habitats are exposed to temperatures below 5 ◦ C [1], and for this reason cold-adapted microorganisms have developed unique physiological tools to survive in these harsh conditions. Many psychrophiles have been reported to produce outer membrane vesicles (OMVs) [8]. It has been reported that the OMVs produced by a cold-adapted bacterium contain putative proteolytic enzymes, which can serve to degrade high molecular weight molecules present in the surrounding cells [9,10] helping the bacterium in the survival of such harsh conditions.

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