The Vibrio vulnificus biotype 2 serovar E gne but not galE is essential for lipopolysaccharide biosynthesis and virulence

Universidad de Valencia Departamento de Microbiología y Ecología c/Dr.Moliner, 50, Burjasot, Valencia, Universidad de Barcelona. Departamento de Microbiología, Diagonal 645, 08071 Barcelona. SPAIN

^* To whom correspondence should be addressed. Email: carmen.amaro{at}uv.es.

	Abstract

This work aimed to establish the role of gne (UDP-GalNAc 4-epimerase activity) and galE (UDP-Gal-4-epimerase activity) in the biosynthesis of surface polysaccharides as well as in virulence for eels and humans of the zoonotic serovar of Vibrio vulnificus biotype 2, serovar E. DNA sequence data revealed that gne and galE are quite homologous within the species (homologies equal or higher than 90%). Mutation in gne of strain CECT4999 increased surface hydrophobicity, produced deep alterations in the outer membrane architecture as well as a noticeable increase in sensitivity to microcidal peptides (MP), to eel and human serum and to phagocytosis/opsonophagocytosis. Furthermore, a significant attenuation in virulence for eels and mice was observed. By contrast, mutation in galE did not alter the cellular surface, did not increase sensitivity to MP, serum or phagocytosis and did not affect virulence degree for fish and mice. The change to attenuated-virulence phenotype produced by a mutation in gne was correlated to the loss of the O-antigen LPS while the capsule was maintained. Complementation of gne-deficient mutant restored the LPS structure together with the whole virulent phenotype. In conclusion, gne but not galE is essential for LPS biosynthesis and virulence in the zoonotic serovar of V. vulnificus biotype 2.