Abstract
BackgroundCyclospora cayetanensis is an important cause for diarrhea in children in developing countries and foodborne outbreaks of cyclosporiasis in industrialized nations. To improve understanding of the basic biology of Cyclospora spp. and development of molecular diagnostic tools and therapeutics, we sequenced the complete apicoplast and mitochondrial genomes of C. cayetanensis.MethodsThe genome of one Chinese C. cayetanensis isolate was sequenced using Roche 454 and Illumina technologies. The assembled genomes of the apicoplast and mitochondrion were retrieved, annotated, and compared with reference genomes for other apicomplexans to infer genome organizations and phylogenetic relationships. Sequence variations in the mitochondrial genome were identified by comparison of two C. cayetanensis nucleotide sequences from this study and a recent publication.ResultsThe apicoplast and mitochondrial genomes of C. cayetanensis are 34,155 and 6,229 bp in size and code for 65 and 5 genes, respectively. Comparative genomic analysis showed high similarities between C. cayetanensis and Eimeria tenella in both genomes; they have 85.6 % and 90.4 % nucleotide sequence similarities, respectively, and complete synteny in gene organization. Phylogenetic analysis of the genomic sequences confirmed the genetic similarities between cecum-infecting avian Eimeria spp. and C. cayetanensis. Like in other coccidia, both genomes of C. cayetanensis are transcribed bi-directionally. The apicoplast genome is circular, codes for the complete machinery for protein biosynthesis, and contains two inverted repeats that differ slightly in LSU rRNA gene sequences. In contrast, the mitochondrial genome has a linear concatemer or circular mapping topology. Eight single-nucleotide and one 7-bp multiple-nucleotide variants were detected between the mitochondrial genomes of C. cayetanensis from this and recent studies.ConclusionsThe apicoplast and mitochondrial genomes of C. cayetanensis are highly similar to those of cecum-infecting avian Eimeria spp. in both genome organization and sequences. The availability of sequence data beyond rRNA and heat shock protein genes could facilitate studies of C. cayetanensis biology and development of genotyping tools for investigations of cyclosporiasis outbreaks.
Highlights
Cyclospora cayetanensis is an important cause for diarrhea in children in developing countries and foodborne outbreaks of cyclosporiasis in industrialized nations
A search of reads from Roche 454 sequencing revealed that there are 33 bp between the closer ends of the two inverted repeats (IR). This allowed the construction of the full circular apicoplast genome of C. cayetanensis
The presence of two IRs was confirmed by mapping of sequence reads to the assembled contigs, as the two IRs differed by eight nucleotides in a 58-bp region of the LSU rRNA gene (Table 1)
Summary
Cyclospora cayetanensis is an important cause for diarrhea in children in developing countries and foodborne outbreaks of cyclosporiasis in industrialized nations. It is endemic in many developing countries, responsible for significant morbidity in children and AIDS patients [1, 2] It is a major cause of foodborne diarrheal illnesses in industrialized nations, especially in North America. The lack of molecular diagnostic tools for case-linkage and trace-back investigations of outbreaks has hampered responses from public health and regulatory agencies such as the U.S Food and Drug Administration and Centers for Disease Control and Prevention. This was exemplified in two recent large multistate outbreaks of cyclosporiasis in 2013 and 2014 in the United States [4] (http://www.cdc.gov/ parasites/cyclosporiasis/outbreaks/index.html)
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