Complete Genome Sequencing Provides Novel Insight into the Virulence Repertories and Phylogenetic Position of Dry Beans Pathogen Curtobacterium flaccumfaciens pv. flaccumfaciens

Bacterial wilt of dry beans (family Fabaceae) caused by the actinobacterial agent Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) is one of the most important diseases threatening edible legume production around the globe. Despite the economic losses due to the bacterial wilt disease, the pathogen has not so far been investigated for its genomic features, pathogenicity determinants and virulence strategies. Here we present the first complete genome sequence of a highly virulent bacteriocin-producing Cff strain P990. The bacterium has a circular chromosome consisting 3,736 kbp with the G+C% content of 71.0%. Furthermore, a 147 kbp circular plasmid (pCff1) with 66.1% G+C% content as well as two circular plasmid-like DNAs with the size of 25 kbp and 22 kbp were detected within the genomic contents of Cff. Phylogenetic analyses revealed that only a few number of Curtobacterium sp. strains deposited in the public databases could be classified within the species C. flaccumfaciens. Comparative genomics of Cff using the genome sequences of actinobacterial plant pathogens revealed the presence of a set of unique low G+C% content genomic islands in the Cff genome. Homologues of pathogenicity-determinant loci capable of producing 1,4-beta-xylanase (xysA), pectate lyase (pelA1 and pelA2), serine protease (chpC, chpG, and pat-1), and sortase (srtA) were detected in Cff genome. The genomic data presented here extends our understanding of the Cff genomic features and pave the ways of research on functional and interaction genetics to combat the risk of bacterial wilt disease in the 21st Century's dry bean industry.