Completed genomes for Rickettsia rickettsii isolated from ticks and quality controlled for motility phenotype

Abstract

Complete genomes of Rickettsia rickettsii were sequenced with Illumina and PacBio technologies from low-passage isolates from ticks. These isolates were quality controlled for intact roaM, a regulator of actin-based motility that is negatively selected for in culture. The Sheila Smith strain was re-sequenced using the same methodology.

Keywords: Rickettsia; genome; tick isolate.

Fig 1

Confirmation of roaM genotype and spreading behavior. (A) Schematics of roaM genotype for previously studied and newly sequenced strains above example photographs of plaque phenotypes from R. rickettsii strains grown on Vero 81 cell monolayers in six-well dishes, stained with MTT 8 d post-infection (1). Scale bar 1 cm. (WT, wild type; PM, point mutation). (B) Immunofluorescence images of R. rickettsii strains infecting Vero cell monolayers. R. rickettsii-infected Vero cells on coverslips were prepared and stained with 1  µg/mL MAb 13-2 (rOmpB) (5), Alexa Fluor 568 phalloidin (Thermo Fisher, A12380), and 1 µg/mL DAPI as previously described (1). Coverslips were imaged at Nyquist sampling on a Zeiss LSM 880 Confocal Microscope, and images were deconvolved using Huygens Professional (Scientific Volume Imaging). Scale bar, 20 µm; scale bar of inset images, 2 μm. (C) Phylogenetic relationship of current R. rickettsii completed genomes. Source and geographical location from which strains were originally obtained are listed with background colors representing groupings of sequenced strains. Bootstrap values are displayed at node branches, and scale bar represents genetic distance.