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Nitrification in continuous culture : the effect of pH and surface growthKeen, G. Anne January 1984 (has links)
A detailed kinetic analysis was made of growth of Nitrosomonas europaea and Nitrobacter sp. in chemostat culture. Steady states were established at a number of dilution rates as measured by substrate concentration and cell number. Biomass concentration was also estimated at each dilution rate and these data were used to evaluate the kinetic growth constants; maximum specific growth rate (m), saturation constant (Ks), true growth yield (Yg) and maintenance energy coefficient (me). The transient response to dilution rate changes was monitored and step increases in dilution rate always resulted in substrate overshoots which were mirrored by cell number undershoots. Step reductions in dilution rate resulted in monotonic changes in substrate concentration to lower steady state levels. Nitrobacter exhibited different growth characteristics when cultured continuously in an airlift column fermenter. This was considered to result from biomass settling within the column, resulting from inadequate mixing. Kinetic growth constants for culture of Nitrobacter in the airlift column fermenter were determined. The optimum pH for nitrite oxidation in batch culture was pH 7.5 with no growth at pH values less than 6.0. Nitrite steady states were established in continuous culture at pH 8.0, 6.0 and 5.5, with washout occurring at pH 5.0 and transient nitrite undershoots were observed following pH changes imposed. Surface growth of Nitrobacter was investigated in batch and continuous culture. Attachment and growth on glass and anion exchange resin surfaces resulted in the development of attached microcolonies. Biofilm development on anion exchange resin surfaces was facilitated by slime production which may assist in the irreversible attachment of cells. The specific rate of nitrite oxidation of cells attached to glass surfaces in batch culture was 20-25% greater than that of freely suspended cells. The enhanced activity of attached cells was independent of pH and pH-activity curves of free and attached cells were similar. Similarly cells attached to anion exchange resins in continuous culture exhibited increased oxidation rates per cell, compared to free cells cultured in the same system. Attachment to surfaces significantly lowered the minimum pH for nitrite oxidation and increased protection against low pH, Reduction in pH to 3.5 prevented nitrite oxidation, however cells remained viable and a steady state was subsequently established at pH 4.5.
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The effect of inoculating alfalfa seed with Rhizobium melilotiBrown, Spencer Lawrence, 1942- January 1976 (has links)
No description available.
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The bacteria of Nebraska soil with special reference to the fixation of nitrogen, annomification, denitrification and in non-protein media Including observations on the reduction of nitrates by soil bacteria in general.Putnam, John Jacob, January 1913 (has links)
Thesis (Ph. D. 1913)--University of Nebraska.
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Studies on nitrite utilization by soil microorganisms.Bulpitt, Sally Erika 01 January 1969 (has links) (PDF)
No description available.
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Properties of methyl bromide cooxidation by ammonia-oxidizing bacteriaDuddleston, Khrystyne Noel 04 August 1998 (has links)
Graduation date: 1999
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Multiple large DNA molecules of AzospirillumWood, Alvin Gleave, January 1982 (has links)
Thesis (Ph. D.)--University of Florida, 1982. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 60-66).
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Responses of Nitrifying Bacteria to Aquaculture Chemotherapeutic AgentsCheatham, Amy Kathleen 06 May 2009 (has links)
As in any animal production industry, disease is inevitable; therefore, it is imperative that aquaculturists are able to effectively manage the disease and maintain their high production levels in an effort to bridge the gap between supply and demand in the seafood industry that has been caused in part by global over-fishing. This management responsibility lies not only in understanding the impact of the treatment on the cultured species, but also in understanding the impact of the treatment to the aquaculture system as an ecosystem. Currently, there is a narrow variety of chemicals approved by either the Food and Drug Administration (FDA) or the Environmental Protection Agency (EPA) for the treatment of disease outbreaks and water quality issues in aquaculture. Approved chemotherapeutants include oxytetracycline, Romet-30®, copper, and formalin. Additionally, a number of chemicals, such as Chloramine-T and potassium permanganate, are used off-label for the treatment of aquaculture systems. In this research, these six more commonly used chemotherapeutants were analyzed for their impacts to the nitrifying bacteria in aquaculture systems.
It was found that three of the chemotherapeutants: oxytetracycline, Romet-30®, and chelated copper caused inhibition to the nitrifying bacteria at the whole cell level as demonstrated in the results from water quality and specific oxygen uptake rate analyses. The nitrification process resumed once the chemotherapeutant was removed from the system, either by a mandatory water change or by natural degradation. The other three chemicals: formalin, Chloramine-T, and potassium permanganate did not result in any significant inhibition to the nitrification process. Experiments on laboratory-cultured nitrifying bacteria confirmed these findings. These experiments also resulted in the observation that the expression of amoA was upregulated by the copper exposure and inhibited by oxytetracycline and Romet-30®, but began to resume as the antibiotics degraded. Comprehensively, the findings of these analyses demonstrated that, although nitrifiers are well-known to be sensitive to their environment, the ability of nitrifying bacteria to continue their oxidative processes following exposure to chemical stress is inherent to the bacteria themselves rather than simply occurring under the protection of a biofilm community as has been suggested. / Ph. D.
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Role of marine nitrifying bacteria in a closed system with Penaeus monodon.Pillay, Balakrishna. 21 October 2013 (has links)
In recent years there has been widespread interest in rearing aquatic
organisms of nutritional and commercial value (Calaprice, 1976). The
most hopeful prospect for marine prawn culture in the United Kingdom
(Wickins, 1976), the Americas (Hanson & Goodwin, 1977) and South
Africa probably lies in intensive culture under controlled conditions.
A closed system approach, in which a captive body of water is circulated,
provides the scope for water quality management which results ~n
maximum water utilization and minimal discharge. On the other hand,
direct utilization of sea-water in open systems presents problems for
aquaculture since this water is subjected to diurnal and seasonal fluctuations
in temperature, salinity and turbidity, as well as contamination
from industrial, agricultural and maritime sources. Furthermore,
large mariculture farms release enormous amounts of organic wastes which
result in eutrophication and could lead to environmental deterioration
of coastal waters (Gerhardt, 1978).
It is well established that circulated sea-water develops an unusual
~on~c composition as a result of the metabolic activity of the prawns
and of the nitrifying bacteria in the biological filter. The changes
include elevated levels of ammonia, nitrite and nitrate and reduced pH.
The presence of even sublethal levels of these nitrogenous compounds ~n
closed systems have been found to affect growth of penaeid spec~es
(Wickins, 1976). Ammonia and nitrite, which rapidly accumulate in the
water, are usually maintained at nontoxic levels by nitrification in
the biological filters (Spotte, 1974; Johnson & Sieburth, 1974). The
chemolithotrophic bacteria responsible for nitrification are presently
classified by their · cellular morphology and by the oxidation of either
ammonia and nitrite (Watson, 1974). The predominant ammonia- and
nitrite-oxidizing bacteria isolated from natural environments are
Nitrosomonas europaea and Nitrobacter winogradskyi, respectively (Watson
et aZ., 1981). Direct observation of nitrifying bacteria in natural
environments, however, has been limited to studies involving light
microscopy with immunofluorescent techniques (Fliermans et aZ., 1974;
Fliermans & Schmidt, 1975).
The electron microscopic observation of nitrifying bacteria ~sdifficult
in natural microcosms with low levels of nitrification and with the
presence of sunlight and anaerobic conditions conducive to the enrichment
of other bacteria with a similar ultrastructure. However, in
closed systems with extremely active nitrification but poor light conditions,
the occurrence of morphologically similar forms in numbers
that could be easily detected by electron microscopy is unlikely
(Johnsort & Sieburth, 1976). Furthermore, the cyst-like colonies of the
nitrifiers are unique and are not found with the methane-oxidizing
bacteria with a similar ultrastructure (Davies & Whittenbury, 1970;
Smith & Ribbons, 1970), whereas the thick cell wall of the cyanobacteria
(Carr & Whitton, 1973) and the distinctive cell morphologies of the
purple sulphur and purple nonsulphur bacteria (Pfennig, 1967) separate
them from the nitrifiers. Therefore, closed systems with active nitrification
provide the ideal environment to study the activities of nitrifiers
in conjunction with their relative abundance, nature and diversity.
In spite of the opportunity offered by closed systems, previous studies
(Kawai et aZ., 1965; Wickins, 1976; Gerhardt, 1978; Mevel & Chamroux,
1981) on nitrification have been primarily indirect observations on
rates of ammonia and nitrite oxidation to nitrate (Johnson & Sieburth,
1976). Studies on the enumeration and identification of nitrifiers ~n
closed systems have been seriously neglected. Kawai et aZ. (1964)
included the enumeration of nitrifiers in their study on nitrification
while,in a qualitative study, an attempt to identify the in situ nitrifiers
1n closed systems (Johnson & Sieburth, 1976) was not very successful.
This study was undertaken to investigate the three basic aspects of
nitrification necessary for the understanding of such a process in closed
systems, viz., the oxidation of ammonia and nitrite to nitrate, and the
enumeration and identification of the nitrifying bacteria. Prior to
determining the concentrations of the nitrogenous compounds in the
culture water, various methods were evaluated for their accuracy and
reproducibility with both sea-water and culture water samples. This
approach is necessary in order to gauge the accuracy of results obtained
by such methods. Enumeration of nitrifying bacteria was preceded by an
investigation on the effect of incubation time on the maximum most
probable number , estimate. Such an investigation was necessary
because of the inconsistent approach to the enumeration of nitrifiers in
previous studies (Wilson, 1927; Walker et al., 1937; Lewis & Pramer,
1958; Molina & Rovira, 1964; Meiklejohn, 1965; Smith et al., 1968).
Incubation periods appear to have been chosen arbitrarily in previous
investigations. Identifi~ation of nitrifying bacteria necessitates the
isolation and purification of these organisms. Isolation of nitrifiers
1S a difficult and time-consuming task (Watson et al., 1981) and could
be the main reason for not being included in previous studies on nitrification.
Since the success of this study depended upon the isolation
and purification of these chemolithotrophs, this aspect is de~lt with
in detail.
The changes most likely to be associated with nitrification in a closed
system were also monitored 1n the culture water. These included pH,
dissolved oxygen and biochemical oxygen demand. Apart from a biological
sand filter, no other form of culture water treatment was effected
during the investigation. The effect of growing the "sugpo" or jumbo
tiger prawn, Penaeus monodon (Kinne, 1977) for 22 weeks in a captive
body of sea-water was evaluated by comparing the survival and wet mass
with those reported by other workers.
This study differs greatly from previous reports on nitrification in
closed systems because both the "causes" and "symptoms" of this important
detoxifying process are investigated. It is intended that the
findings of such a study would aid culturists in exploiting the nitrifying
potential of closed systems to its utmost. / Thesis (M.Sc.)-University of Durban-Westville, 1984.
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An investigation of carbon and nitrogen metabolism through a genomic analysis of the genus Nitrobacter /Starkenburg, Shawn R. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 120-137). Also available on the World Wide Web.
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Multistage and multiple biomass approaches to efficient biological nitrogen removal using biofilm cultures /Hughes, Leonie. January 2008 (has links)
Thesis (Ph.D)--Murdoch University, 2008. / Thesis submitted to the Faculty of Sustainability, Environmental and Life Sciences. Includes bibliographical references (p. 213-220).
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