Isolation and Complete Genome Sequence Analysis of Kosakonia cowanii Pa82, a Novel Pathogen Causing Bacterial Wilt on Patchouli

Abstract

<i>Pogostemon cablin</i> (patchouli), an important medicinal and aromatic plant, is widely used in traditional Chinese medicine as well as in perfume industry. Patchouli plants are susceptible to bacterial wilt disease, which causes significant economic losses by reduction in yield and quality of the plant products. However, few studies focus on the pathogens causing bacterial wilt on patchouli. In this study, strain Pa82 was isolated from diseased patchouli plants with typical bacterial wilt symptoms in Guangdong province, China, and was confirmed to be a highly virulent pathogen of patchouli bacterial wilt. Comparative sequence analysis of 16S rRNA gene showed that the strain was closely related to <i>Kosakonia</i> sp. CCTCC M2018092 (99.9% similarity) and <i>Kosakonia cowanii</i> Esp_Z (99.8% similarity). Moreover, phylogenetic tree based on 16S rRNA gene sequences showed that the strain was affiliated with genus <i>Kosakonia</i>. Further, the whole genome of strain Pa82 was sequenced, and the sequences were assembled and annotated. The complete genome of the strain consists of one chromosome and three plasmids. Average nucleotide identity (ANI) and phylogenetic analysis revealed that the strain belongs to <i>Kosakonia cowanii</i> (designated <i>Kosakonia cowanii</i> Pa82). Virulence-related genes of the strain involved in adherence, biofilm formation, endotoxin and other virulence factors were predicted. Among them, <i>vgrG</i> gene that encodes one of the type VI secretion system components was functionally validated as a virulence factor in <i>Kosakonia cowanii</i> Pa82 through construction of Tn<i>5</i> insertion mutants and identification of mutant defective in virulence.