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Comparative genomic hybridizations of Mycobacterium avium isolates obtained from multiple host species

ABSTRACT: A comparative genomic approach was used to identify large sequence polymorphisms among Mycobacterium avium isolates obtained from a variety of host species. DNA microarrays were used as a platform for comparing mycobacteria field isolates with the sequenced bovine isolate Mycobacterium avium subsp. paratuberculosis (Map) K10. ORFs were classified as present or divergent based on the relative fluorescent intensities of the experimental samples compared to Map K10 DNA. Map isolates cultured from cattle, bison, sheep, goat, avian, and human sources were hybridized to the Map microarray. Three large deletions were observed in the genomes of four Map isolates obtained from sheep and four clusters of ORFs homologous to sequences in the Mycobacterium avium subsp. avium (Maa) 104 genome were identified as being present in these isolates. One of these clusters encodes glycopeptidolipid biosynthesis enzymes. One of the Map sheep isolates had a genome profile similar to a group of Mycobacterium avium subsp. silvaticum (Mas) isolates which included four independent laboratory stocks of the organism traditionally identified as Maa strain 18. Genome diversity in Map appears to be mostly restricted to large sequence polymorphisms that are often associated with mobile genetic elements. Keywords: Comparative genomic hybridization

ORGANISM(S): Mycobacterium avium subsp. avium Mycobacterium avium subsp. paratuberculosis Mycobacterium avium

PROVIDER: GSE7622 | GEO | 2007/04/27

SECONDARY ACCESSION(S): PRJNA100243

REPOSITORIES: GEO

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Project description:Mycobacterium avium subspecies paratuberculosis (MAP) infection is established following the ingestion of bacteria, their penetration of the intestinal mucosa and subsequent events of the host-parasite interaction. These bacteria invade M cells, macrophages and are capable of resisting host defenses and multiply to reach very high numbers intracellular. Mycobactrium avium subsp. avium (MAA) is an antigenically and genetically similar organisms but is relatively nonpathogenic for cattle. MAA organisms appear to infect cattle, but unlike cattle infected with MAP, cattle infected with MAA typically mount an effective systemic immune response, form caseous granuloma, and eliminate the infection. This study was designed to understand the similarities and differences in the host responses during MAP and MAA infection. Neonatal calves were infected (ligated ileal loops) with PBS, MAP, or avirulent MAA following which samples were collected at 30 min, 1h, 2h, 4h, 8h, or 12h. Post-infection, RNA was collected, processed, and then hybridized to custom bovine gene expression arrays, each of which represented 13,258 transcripts spotted in duplicate. Arrays were normalized by scaling against the average reference intensity value (i.e., average across all arrays), normalized by global mean, and then log transformed before statistical analyses were performed. Pairwise comparisons of averaged signal values and StudentM-bM-^@M-^Ys t test were performed using GeneSifter software (VizX Labs, Seattle, WA). A fold-change of at least 1.5-fold and a p value of 0.05 or less was required for a difference in signal to be considered statistically significant. When comparing the transcriptional responses of calves infected with the MAA versus MAP, unique patterns of expression were clearly visible. In general, numbers of transcripts altered in response to infection were much greater for MAA-infected animals than for those infected with the MAP. No genes were significantly up-regulated in MAP-infected animals at the earliest time point tested (30 min), and only modest numbers of genes were increased in expression over the experimental time course. On the other hand, up-regulated transcripts were detected by 30 min in MAA-infected animals and peaked by 2 hr. Differences in the numbers of down-regulated genes between MAP-infected and MAA-infected animals (compared to PBS-infected controls) were less pronounced. At the earliest time points, MAP-infected calves had a greater number of down-regulated genes than did animals infected with MAA. This trend was reversed at 8 and 12 hr post-infection. Keywords: Gene expression profiling by microarray Microarrays were used to examine the transcriptional profiles of bovine intestinal mucosa inoculated with PBS, MAP or MAA and across six time points (30 min, 1, 2, 4, 8, and 12 hours). Experiments were performed in quadruplicate for PBS, MAP, and MAA (bovine ligated ileal loops surgeries were performed with four calves). For one surgery, MAA was used for 4 time ponts only, thus generateing a total of 70 arrays.

Project description:Mycobacterium avium subspecies paratuberculosis (MAP) infection is established following the ingestion of bacteria, their penetration of the intestinal mucosa and subsequent events of the host-parasite interaction. These bacteria invade M cells, macrophages and are capable of resisting host defenses and multiply to reach very high numbers intracellular. Mycobactrium avium subsp. avium (MAA) is an antigenically and genetically similar organisms but is relatively nonpathogenic for cattle. MAA organisms appear to infect cattle, but unlike cattle infected with MAP, cattle infected with MAA typically mount an effective systemic immune response, form caseous granuloma, and eliminate the infection. This study was designed to understand the similarities and differences in the host responses during MAP and MAA infection. Neonatal calves were infected (ligated ileal loops) with PBS, MAP, or avirulent MAA following which samples were collected at 30 min, 1h, 2h, 4h, 8h, or 12h. Post-infection, RNA was collected, processed, and then hybridized to custom bovine gene expression arrays, each of which represented 13,258 transcripts spotted in duplicate. Arrays were normalized by scaling against the average reference intensity value (i.e., average across all arrays), normalized by global mean, and then log transformed before statistical analyses were performed. Pairwise comparisons of averaged signal values and Student’s t test were performed using GeneSifter software (VizX Labs, Seattle, WA). A fold-change of at least 1.5-fold and a p value of 0.05 or less was required for a difference in signal to be considered statistically significant. When comparing the transcriptional responses of calves infected with the MAA versus MAP, unique patterns of expression were clearly visible. In general, numbers of transcripts altered in response to infection were much greater for MAA-infected animals than for those infected with the MAP. No genes were significantly up-regulated in MAP-infected animals at the earliest time point tested (30 min), and only modest numbers of genes were increased in expression over the experimental time course. On the other hand, up-regulated transcripts were detected by 30 min in MAA-infected animals and peaked by 2 hr. Differences in the numbers of down-regulated genes between MAP-infected and MAA-infected animals (compared to PBS-infected controls) were less pronounced. At the earliest time points, MAP-infected calves had a greater number of down-regulated genes than did animals infected with MAA. This trend was reversed at 8 and 12 hr post-infection. Keywords: Gene expression profiling by microarray

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Comparative genomic hybridizations of Mycobacterium avium isolates obtained from multiple host species

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