Molecular basis of strain variations of a chlamydial pathogen of arthropods

Variations between strains have been extensively studied in human pathogens mainly because even genomically highly identical strains can cause severely different phenotypes in their hosts. Here we investigate within-species diversity in Rhabdochlamydia porcellionis a pathogen infecting terrestrial isopods and a member of the phylum Chlamydia that also includes well-known human pathogens as Chlamydia trachomatis. Using an infection assay in Sf9 insect cell cultures we could show that albeit there are only few genomic variations, the strains 15C and ZGO cause different phenotypes. To investigate potential underlying mechanisms we carried out a global gene expression analysis and could show that changes in major metabolic pathways help strain 15C to replicate more efficiently in the host cells. In addition we found that genes shown to be involved in pathogenicity and host interaction of human pathogenic chlamydia i.e. genes encoding the type III secretion system and polymorphic membrane proteins are regulated differently by the strains. Comparative gene expression profiling analysis of RNA-seq data for the two strains of Rhabdochlamydia porcellionis 15C and ZGO.