Flea-borne microbe that causes human disease. Rickettsia felis URRWXCal2 strain:URRWXCa12

Rickettsia felis strain URRWXCa12. The genome of Rickettsia felis strain URRWXCa12 (strain California 2) reveals some unusual features. There are two plasmids (pRF and pRFdelta), the first such identified in the Rickettsia genus, and the pRF plasmid has genes that encode proteins similar to those found on conjugative plasmids such as TraA from Agrobacterium tumefaciens, F plasmid TraD and TraG, and the chromosome encodes proteins similar to the vir genes of A. tumefaciens. The chromosome encodes a protein that is similar to the IncP plasmid primase protein TraC. All of these functions may be involved in pathogenesis and the movement of proteins and DNA and electron microscopy confirmed the evidence of a conjugative pilus in this organism as well as other fimbriae. The genome exhibited a large number of repetitive elements, including 82 transposase genes, and genomic comparisons with other Rickettsia indicates a large number of inversions and translocations. These were many Rickettsia palindromic elements (RPEs) found in the genome as well as a large number of surface antigen (sca) genes including split genes that were shown to be transcribed, and genes encoding tricoriticopeptide repeat proteins (TPR) and ankyrin-repeat proteins, both of which may be involved in infection processes. Many global metabolic regulators were also discovered, including fourteen spoT paralogs that regulate cellular metabolism in Escherichia coli in response to starvation conditions and all fourteen were found to be transcribed. Sixteen toxin and fourteen anti-toxin genes were discovered that potentially may be involved in maintaining the presence of the bacteria in the host; possibly by targeting the host cell or in synchronizing the bacterial replication cycles.