Lawrence, Anne C. (1978) Microbial diversity : a consequence of the aquatic environment. PhD thesis, University of Warwick.

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Abstract

Although prosthecate bacteria have been observed in freshwater
environments, questions concerning the function or survival value of
these integral cellular extensions are unresolved. However, it is
now becoming apparent that this group of microorganisms forms
part of a highly speciallsed indigenous population.
An electron microscope survey of the bacterial population from
several oligotrophic water bodies has shown that Hyphomicrobiurn and
Caulobacter species constitute up to 20% of such populations, the
percentage being correlated with the nutrient status of the system.
The multiappendaged genera, at best, approach 1% of the total
microbial population. 'Enrichment' systems to which no nutrients
have been added, select for the latter. Several isolates of multiappendaged
bacteria have been obtained from such systems. Studies
on one of these has shown that gross phenotypic variation can be
brought about by varying the nutrient status of the culture medium.
These studies have shown that the prosthecae can be induced or
repressed by environmental stimull. This phenotypic variation
consequently makes the estimation, simply on morphological grounds,
of the incidence of multiappendaged bacteria in the environment
difficult. It almost certainly leads to gross underestimates of numbers.
Similarly, studies on Hyphomtcroblum have demonstrated that this
prosthecate bacterbin not only exhibits differentiation which is obligate
to the cell cycle, but is also capable of environmentally induced
differentiation.
These observations also highlight a fundamental split concerning
prosthecal function: - (i) where prosthecal formation is obligate and
intimately involved in the cell cycle. e.g. Caulobacter and
Hyphomicroblum and (ii) where prosthecae are non-obligate and
environmentally induced, e.g. the multiappendaged bacteria,
Ancalomicrobium.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QR Microbiology
Library of Congress Subject Headings (LCSH):	Gram-negative bacteria, Microbial diversity
Official Date:	May 1978
Dates:	Date Event May 1978 Submitted
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Dow, Crawford S.
Sponsors:	Natural Environment Research Council (Great Britain) (NERC)
Extent:	299 leaves
Language:	eng

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