Previous research performed in 1999 by Harris et al. has shown that
many varieties of ruminants serve as the host species for Mycobacterium avium
subspecies paratuberculosis (MparaTb) infections. Gene sequencing has
supported the contention that organisms isolated from different hosts harbor
different gene sequences; this has been exemplified by Amonsin et al. in 2004
with the sequencing of the mfd (transcription-repair coupling factor) and by
Motiwala et al. in 2005 through sequence analysis of phosphatidylethanolaminebinding
proteins which reveal a host-specific correlation of isolates. Some
contradicting reports from Bannantine et al. from 2003 have further claimed that
MparaTb is a monogenic organism based upon sequence data from regions
flanking the origin of replication and the 16s rRNA. One of the drawbacks to the
techniques implemented in these reports is the extremely restricted region of the
bacterial genome that was analyzed; furthermore, only a select number of
isolates were analyzed. In the present studies, amplified fragment length polymorphism (AFLP) was used as a tool for a genome scale comparison of
MparaTb isolates from differing isolation types as well as a comparison of
MparaTb isolates to the genetically similar yet avirulent Mycobacterium avium
subspecies avium isolates. AFLP data reveals the MparaTb genome to be
much more plastic and polymorphic than previously thought. These polymorphic
regions were identified and characterized and are shown to be unique to the
organism when compared to an array of Mycobacterial isolates of differing
species. These polymorphic regions were also utilized in polymerase chain
reaction (PCR) based diagnostic as well as epidemiologic tests. Furthermore,
AFLP comparative analysis of intracellular and fecal MparaTb isolates reveals
polymorphic regions unique to each isolate type. While these genomic
differences are not based upon differences in the genetic code, they are based
upon epigenetic modifications such as DNA methylation. These DNA
methylation patterns are unique to intracellular MparaTb isolates as opposed to
isolates from fecal material. Furthermore, AFLP comparisons of fecal MparaTb
isolates that were passaged through the bovine ileum revealed banding pattern
differences as compared to the original inoculum.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2612 |
| Date | 15 May 2009 |
| Creators | O'Shea, Brian James |
| Contributors | Ficht, Tom, Rice-Ficht, Allison |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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