Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Poster: Microbial Sequencing and Genome Programs
Anaplasma marginale causes anaplasmosis, the most prevalent tick-transmitted disease of cattle worldwide. Because A. marginale is an obligate intracellular bacteria, contamination of bacterial DNA with host cell DNA is a significant problem, which makes whole genome shotgun sequencing unsuitable. Therefore we have chosen a targeted Bacterial Artificial Chromosome library approach to sequence the A. marginale genome. Sequence to date has shown that A. marginale has a G + C content of 49% and a gene density of 1.2 ORFs/kb predicting a total of 1440 ORFs. Because outer membrane protein preparations have been shown to induce solid protection against A. marginale challenge, we focused our initial genome sequencing efforts on identifying determinants of outer membrane proteins and selected five BAC clones containing the Major Surface Protein (MSP) genes: msp1a, msp1b, msp2, msp4 and msp5. We identified 3 structural homologs of the msp1a gene immediately 3' to this gene. Two of these homologs have low levels of sequence identity with msp1a. Furthermore the sequence data allowed us to determine the structural composition of the msp2 gene family: that of a single operon linked expression site and multiple truncated pseudogenes. The same arrangement seems to apply for the msp3 gene family, although the expression site for msp3 has not yet been identified. We identified a recurring motif of a msp3 pseudogene in a tail to tail arrangement with a msp2 pseudogene, and demonstrated that the msp2 pseudogenes are recombined into the functional expression site to provide antigenic variation.