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Biofilms in the potable water distribution network
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Jakubovics, Nicholas S. (1998) Biofilms in the potable water distribution network. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b1370116~S1
Abstract
The roles of vegetative dormancy and attachment to surfaces in the survival and
growth of bacteria in potable water systems were investigated. Species present in the
water were identified following isolation or direct observation of static batch
enrichment cultures. Using the latter approach, many prosthecate and other stalked
bacteria were found. Prosthecate bacteria undergo bi- or poly-phasic life cycles
involving asymmetric division to produce reproductive cells and dormant swarmer
cells and their presence in tap water supports the theory that vegetative dormancy is
an important survival mechanism in this environment. A continuous flow model was
established to analyse the metabolic activity of planktonic and attached bacteria in
potable water. A physiological dye, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC),
was shown to stain active cells specifically in batch cultures of a Sphingomonas sp.
and Caulobacter crescentus. Unsuccessful attempts were made to identify cellular
proteins of Sphingomonas sp. cells that were specific to the attached or planktonic
phenotype.
By comparing the total bacterial counts in potable water with the total viable counts it
was shown that a large proportion of the microflora was not cultivable on
heterotrophic media. However, a proportion of these cells became culturable
following enrichment with peptone. After ceasing the exogenous nutrient addition
cellular aggregation occurred, presumably reflecting physiological changes in
response to nutrient depletion. No clear trend in the activity of attached cells during
biofilm development was detected. However, firmly attached cells were buffered
against changes in the chemistry of the water. Growth within biofilms and release
into the water column elevated the concentration of bacteria in the water. Attached
cells were resistant to 0.3 mg free chlorine 1-1 added for 3 hrs, although this did
weaken the architecture of the biofilm. Long term biofilms (one year-old) were
almost devoid of bacteria - an observation that could not be adequately explained.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QR Microbiology | ||||
Library of Congress Subject Headings (LCSH): | Drinking water -- Microbiology, Bacteria -- Physiology, Biofilms | ||||
Official Date: | May 1998 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Biological Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Dow, Crawford S. | ||||
Extent: | xx, 261 p. | ||||
Language: | eng |
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