The diversity and distribution of Mycobacterium species in varying ecological and climatic environments
Khera, Tanya (2012) The diversity and distribution of Mycobacterium species in varying ecological and climatic environments. PhD thesis, University of Warwick.
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The species within the genus Mycobacterium are commonly detected in a
variety of environments including soil, water and dust. Many species within
the group are capable of causing opportunistic diseases and are hypothesised to
be responsible for the reduction in BCG efficacy in tropical countries.
Consequently it is important to understand the diversity and biogeography of
mycobacteria in the environment. Soil and water samples were collected from
a total of 42 residential sites in 9 different climatic regions. To determine
community composition, community DNA was extracted and amplicon
pyrosequencing was employed to target the 16S rRNA gene of the
Mycobacterium genus and slow-growing mycobacteria. Quantitative PCR was
employed to quantify the total abundance of Mycobacterium species and
specifically members of the M. tuberculosis complex.
The study revealed a greater diversity of both fast-growing and slow-growing
mycobacteria than previously reported. Prevalent species in soil were closely
related to the fast growers M. neglectum, M. moriokaense and the slow
growers M. malmoense and M. colombiense, in contrast to water had a high
abundance of sequences related to the fast growers M. aurum sp. ATCC
23070, M. neoaurum and the slow-growers M. gordonae and M. colombiense.
The abundance of the Mycobacterium genus ranged from 3.35 x 101 to 8.01
x108 gene copies per gram/ml. M. bovis was detected in six environmental
samples using qPCR.
Biogeographical analysis demonstrated the importance of elevation and
temperature for the community composition of mycobacteria in soil. A nonlinear
relationship was observed between elevation and the outcome variables
Mycobacterium species richness, diversity and abundance with a peak midelevation.
In contrast latitude was the primary factor to explain the
composition and diversity of mycobacteria in water samples.
To our knowledge this is the first time that the diversity and abundance of
mycobacteria has been elucidated on a large geographical scale using
pyrosequencing and multivariate analyses. Results indicate ample opportunity
for human exposure to mycobacteria with potentially pathogenic species in
soil and water substrates. These results have implications for the risk of
infection and similar biogeographical surveys on a worldwide scale may
provide improved correlations with BCG vaccine efficacy.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QR Microbiology|
|Library of Congress Subject Headings (LCSH):||Mycobacteria -- Ecology|
|Official Date:||September 2012|
|Institution:||University of Warwick|
|Theses Department:||School of Life Sciences|
|Supervisor(s)/Advisor:||Wellington, E. M. H. (Elizabeth M. H.), 1954- ; Courtenay, Orin|
|Extent:||xvii, 254 leaves : illustrations, charts, maps|
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