Aeromonas are bacteria broadly spread in the environment, particularly in aquatic habitats and can induce human infections. Several virulence factors have been described associated with bacterial pathogenicity, such as the Type VI Secretion System (T6SS). This system translocates effector proteins into target cells through a bacteriophage-like contractile structure encoded by tss genes. Here, a total of 446 Aeromonas genome sequences were screened for T6SS and the proteins subjected to in silico analysis. The T6SS-encoding locus was detected in 243 genomes and its genes are encoded in a cluster containing 13 core and 5 accessory genes, in highly conserved synteny. The amino acid residues identity of T6SS proteins ranges from 78 to 98.8%. In most strains, a pair of tssD and tssI is located upstream the cluster ( tssD -2, tssI -2) and another pair was detected distant from the cluster ( tssD -1, tssI -1). Significant variability was seen in TssI (VgrG) C-terminal region, which was sorted in four groups based on its sequence length and protein domains. TssI containing ADP-ribosyltransferase domain are associated exclusively with TssI-1, while genes coding proteins carrying DUF4123 (a conserved domain of unknown function) were observed downstream tssI -1 or tssI -2 and escort of possible effector proteins. Genes coding proteins containing DUF1910 and DUF1911 domains were located only downstream tssI -2 and might represent a pair of toxin/immunity proteins. Nearly all strains display downstream tssI -3, that codes for a lysozyme family domain protein. These data reveal that Aeromonas T6SS cluster synteny is conserved and the low identity observed for some genes might be due to species heterogeneity or its niche/functionality.

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气单胞菌 VI 型分泌系统的计算机比较分析

气单胞菌是在环境中广泛传播的细菌，特别是在水生生境中，可诱发人类感染。已经描述了几种与细菌致病性相关的毒力因子，例如 VI 型分泌系统 (T6SS)。该系统通过由 tss 基因编码的噬菌体样收缩结构将效应蛋白转移到靶细胞中。在这里，共筛选了 446 个气单胞菌基因组序列的 T6SS 和进行计算机分析的蛋白质。在 243 个基因组中检测到 T6SS 编码基因座，其基因编码在一个包含 13 个核心基因和 5 个辅助基因的簇中，高度保守。T6SS 蛋白的氨基酸残基同一性范围为 78% 至 98.8%。在大多数菌株中，一对 tssD 和 tssI 位于簇的上游（ tssD -2，tssI -2) 和另一对远离集群 (tssD -1, tssI -1)。TssI (VgrG) C 末端区域存在显着变异性，根据其序列长度和蛋白质结构域将其分为四组。含有 ADP-核糖基转移酶结构域的 TssI 仅与 TssI-1 相关联，而在 tssI -1 或 tssI -2 下游观察到编码携带 DUF4123（功能未知的保守结构域）的蛋白质的基因，并护送可能的效应蛋白。含有 DUF1910 和 DUF1911 结构域的基因编码蛋白仅位于 tssI -2 下游，可能代表一对毒素/免疫蛋白。几乎所有菌株都显示下游 tssI -3，它编码溶菌酶家族结构域蛋白。