Bioinformatic Analysis of the Type VI Secretion System and Its Potential Toxins in the Acinetobacter Genus

REPIZO, GUILLERMO D.; SALCEDO, SUZANA P.; SERAVALLE, JOANA L.; ESPARIZ, MARTÍN

Frontiers in Microbiology

Frontiers Media SA

Año: 2019 vol. 10 p. 1 - 18

Several Acinetobacter strains are important nosocomial pathogens, with Acinetobacterbaumannii as the species of greatest concern worldwide due to its multi-drug resistanceand recent appearance of hyper-virulent strains in the clinical setting. Acinetobactercolonization of the environment and the host is associated with a multitude offactors which remain poorly characterized. Among them, the secretion systems (SS)encoded by Acinetobacter species confer adaptive advantages depending on theniche occupied. Different SS have been characterized in this group of microorganisms,including T6SS used by several Acinetobacter species to outcompete other bacteriaand in some A. baumannii strains for Galleria mellonella colonization. Therefore, tobetter understand the distribution of the T6SS in this genus we carried out an in-depth comparative genomic analysis of the T6SS in 191 sequenced strains. To thisend, we analyzed the gene content, sequence similarity, synteny and operon structureof each T6SS loci. The presence of a single conserved T6SS-main cluster (T6SS-1),with two different genetic organizations, was detected in the genomes of severalecologically diverse species. Furthermore, a second main cluster (T6SS-2) was detectedin a subgroup of 3 species of environmental origin. Detailed analysis also showed animpressive genetic versatility in T6SS-associated islands, carrying VgrG, PAAR andputative toxin-encoding genes. This in silico study represents the first detailed intra-species comparative analysis of T6SS-associated genes in the Acinetobacter genus,that should contribute to the future experimental characterization of T6SS proteinsand effectors.