CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India.
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
PLoS One. 2021 Feb 11;16(2):e0245727. doi: 10.1371/journal.pone.0245727. eCollection 2021.
The pectinolytic genus Dickeya (formerly Erwinia chrysanthemi) comprises numerous pathogenic species which cause diseases in various crops and ornamental plants across the globe. Their pathogenicity is governed by complex multi-factorial processes of adaptive virulence gene regulation. Extracellular polysaccharides and lipopolysaccharides present on bacterial envelope surface play a significant role in the virulence of phytopathogenic bacteria. However, very little is known about the genomic location, diversity, and organization of the polysaccharide and lipopolysaccharide biosynthetic gene clusters in Dickeya. In the present study, we report the diversity and structural organization of the group 4 capsule (G4C)/O-antigen capsule, putative O-antigen lipopolysaccharide, enterobacterial common antigen, and core lipopolysaccharide biosynthesis clusters from 54 Dickeya strains. The presence of these clusters suggests that Dickeya has both capsule and lipopolysaccharide carrying O-antigen to their external surface. These gene clusters are key regulatory components in the composition and structure of the outer surface of Dickeya. The O-antigen capsule/group 4 capsule (G4C) coding region shows a variation in gene content and organization. Based on nucleotide sequence homology in these Dickeya strains, two distinct groups, G4C group I and G4C group II, exist. However, comparatively less variation is observed in the putative O-antigen lipopolysaccharide cluster in Dickeya spp. except for in Dickeya zeae. Also, enterobacterial common antigen and core lipopolysaccharide biosynthesis clusters are present mostly as conserved genomic regions. The variation in the O-antigen capsule and putative O-antigen lipopolysaccharide coding region in relation to their phylogeny suggests a role of multiple horizontal gene transfer (HGT) events. These multiple HGT processes might have been manifested into the current heterogeneity of O-antigen capsules and O-antigen lipopolysaccharides in Dickeya strains during its evolution.
果胶分解菌属 Dickeya（原欧文氏菌属）包含许多致病种，这些种在全球范围内引起各种作物和观赏植物的疾病。它们的致病性受适应性毒力基因调节的复杂多因素过程控制。细菌包膜表面的细胞外多糖和脂多糖在植物病原细菌的毒力中起着重要作用。然而，关于 Dickeya 中多糖和脂多糖生物合成基因簇的基因组位置、多样性和组织，我们知之甚少。在本研究中，我们报告了来自 54 株 Dickeya 菌株的组 4 荚膜 (G4C)/O-抗原荚膜、假定 O-抗原脂多糖、肠杆菌共同抗原和核心脂多糖生物合成簇的多样性和结构组织。这些簇的存在表明 Dickeya 具有携带 O-抗原的荚膜和脂多糖，将其带到外表面。这些基因簇是 Dickeya 外表面组成和结构的关键调节成分。O-抗原荚膜/G4C 组 4 荚膜 (G4C) 编码区在基因内容和组织上存在差异。基于这些 Dickeya 菌株中核苷酸序列的同源性，存在两个不同的组，G4C 组 I 和 G4C 组 II。然而，除了 Dickeya zeae 外，在 Dickeya spp. 中观察到假定的 O-抗原脂多糖簇的变化相对较少。此外，肠杆菌共同抗原和核心脂多糖生物合成簇主要作为保守的基因组区域存在。O-抗原荚膜和假定 O-抗原脂多糖编码区与其系统发育的变化表明，多次水平基因转移 (HGT) 事件发挥了作用。这些多次 HGT 过程可能在 Dickeya 菌株的进化过程中表现为 O-抗原荚膜和 O-抗原脂多糖的当前异质性。
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