Conservation in the face of diversity: multistrain analysis of an intracellular bacterium

Abstract

Background: With the recent completion of numerous sequenced bacterial genomes, notable advances have been made in understanding the level of conservation between various species. However, relatively little is known about the genomic diversity among strains. We determined the complete genome sequence of the Florida strain of Anaplasma marginale, and near complete (>96%) sequences for an additional three strains, for comparative analysis with the previously fully sequenced St. Maries strain genome.

Anaplasma marginale Superinfection Attributable to Pathogen Strains with Distinct Genomic Backgrounds

“…Stabilates prepared from animals previously experimentally infected (18,21) with single strains (St. Maries, Florida, or Washington-Okanogan) were either analyzed individually or mixed to create three defined strain pairs with equal representation of each strain based on bacteremia levels. DNA was extracted from the single strains or mixed strain pairs and then processed and sequenced as described above.…”

“…Target loci that had previously been shown to be broadly conserved among strains (17,18,23) were initially screened for strain-specific alleles using the complete genome sequences of the St. Maries (GenBank accession no. CP000030) and Florida (CP001079) strains.…”

“…Alternatively, strain A may expand its allelic repertoire on the same genomic background to generate a closely related strain, A=. The latter possibility is supported by msp2 allelic gene duplication within a single strain and the presence of different numbers of msp2 loci and alleles among strains (16)(17)(18)(19). Either strain A= or B would generate the observed increase in the number and diversity of expressed msp2 alleles within the high-prevalence tropical regions (22).…”

“…A. marginale establishes persistent infection within an animal by antigenic variation in the immunodominant surface protein, major surface protein 2 (MSP2), which is generated via gene conversion using a genomic repertoire of distinct msp2 alleles (13)(14)(15)(16). Genomic comparison of multiple strains revealed that although A. marginale has a "closed core" genome with essentially the same gene content among all strains, the repertoire of msp2 alleles is distinct (17,18). Importantly, strains with a distinct msp2 allelic repertoire have been shown experimentally to be capable of strain superinfection, in which a second strain establishes infection in an animal already infected with a primary strain (15,19,20).…”

Complete Genome Sequence of Anaplasma marginale subsp. centrale

“…OpAG1 to OpAG3 and Msp4 are generally well conserved, while the family comprising Omp1 to Omp15 found in senso stricto strains (2,3,8) is reduced in A. marginale subsp. centrale: genes for the closely related proteins Omp7 to Omp9 are collapsed into a single CDS, and genes for homologs of Omp2, Omp3, Omp6, and Omp15 are missing.…”