Baker, Paul (Researcher in biological sciences) (1997) The distribution and diversity of actinomycetes in soil fractions. PhD thesis, University of Warwick.

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Abstract

The results presented were concerned with the survival of Streptomyces coelicolor A3(2)
(pll673) inoculated into soil microcosms, which were destructively fractionated so that
the total propagules and spore counts could be determined in each of the soil fractions.
It was found that this microorganism became associated with the smallest soil aggregates
at the time of inoculation but with incubation of the soil microcosms the mycelia and
spores became attached to the larger soil aggregates. In the sterile soil, the
streptomycete growth was much greater than in nonsterile soil, perhaps due to the
increased supply of nutrients created by autoclaving the soil, and the lack of competition.
Many of the newly formed spores in sterile soil were not attached to the soil aggregates,
which may have enabled them to be distributed to new micro sites.
When the distribution of indigenous actinomycetes in soil was investigated, it ressembled
the distribution of Streptomyces coelicolor in nonsterile soil after the inoculant had been
through one life cycle. Actinomycetes were then isolated from each of the soil fractions,
as well as the unfractionated soil, and each of these strains were identified to genera, if
possible. It was found that many of the micromonosporas and streptosporangia were
isolated from the 63-251 μm soil aggregates, probably because this fraction contained
low eubacterial and streptomycetes populations caused by the low organic content within
this soil fraction. There was a high eubacterial count in the 2-20 μm soil aggregates and
although the actinomycetes were outcompeted within this soil fraction, their diversity
was greatest within this fraction. This diversity was also reflected by their production of
different secondary metabolites.
DNA was extracted from each of the isolates and amplified using specifically designed
primers for high GC microorganisms. Each of the products were individually run on
denaturing gradient gels. It was found that the amplified products from actinomycetes
formed bands on the denaturing gels which migrated to 3 positions. Each of these
positions corresponded to major groups of actinomycetes of which streptomycetes
formed one group. The patterns corresponding to the isolates of each soil fraction would
be compared with the amplified products derived from in situ soil DNA extracts. It was
found that the results were not comparable but this work is still being investigated.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QH Natural history > QH426 Genetics
Library of Congress Subject Headings (LCSH):	Actinobacteria, Streptomyces coelicolor, Streptomyces, Soils -- Analysis
Official Date:	November 1997
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Wellington, E. M. H. (Elizabeth M. H.), 1954- ; Gürtler, Hanne
Sponsors:	Biotechnology and Biological Sciences Research Council ; Novo Nordisk
Extent:	xi, 185 leaves
Language:	eng

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