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Time courses of MeBr consumption (a) and NO2⁻ production (b) by N. europaeaover a 48- to 72-h period. All vials contained 10 mM NH4⁺, phosphate buffer (pH 7.2), 6 × 10⁷ cells of N. europaea ml⁻¹, and either no MeBr (□), 0.11 mM MeBr (■), 0.22 mM MeBr (⧫), or 0.44 mM MeBr (●). The error bars indicate the standard deviations of the means based on the results obtained for three replicate vials per treatment.
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We examined the rates and sustainability of methyl bromide (MeBr) oxidation in moderately low density cell suspensions ( approximately 6 x 10(7) cells ml(-1)) of the NH(3)-oxidizing bacterium Nitrosomonas europaea. In the presence of 10 mM NH(4)(+) and 0.44, 0. 22, and 0.11 mM MeBr, the initial rates of MeBr oxidation were sustained for 12, 12, and...
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Little information exists on the potential of NH3-oxidizing bacteria to cooxidize halogenated hydrocarbons in soil. A study was conducted to examine the cooxidation of methyl
bromide (MeBr) by an NH3-oxidizing bacterium,Nitrosomonas europaea, under soil conditions. Soil and its water content modified the availability of NH4
+and MeBr and influenced...
Citations
... Oxidation of ammonia takes place in two stages ( Figure 2). They are involved in the nitrifying bacteria of the first phase, among which the metabolic abilities of Nitrosomonas europaea were best studied [51][52][53][54]. In the first stage, due to the attachment of the oxygen molecule, ammonia is oxidized to hydroxylamine. ...
... Oxidation of ammonia takes place in two stages ( Figure 2). They are in nitrifying bacteria of the first phase, among which the metabolic abilities o europaea were best studied [51][52][53][54]. In the first stage, due to the attachment molecule, ammonia is oxidized to hydroxylamine. ...
... kcal per mole of oxidiz Therefore, the first phase nitrifiers are equipped with a respiratory sy Oxidation of ammonia takes place in two stages ( Figure 2). They are in nitrifying bacteria of the first phase, among which the metabolic abilities of europaea were best studied [51][52][53][54]. In the first stage, due to the attachment o molecule, ammonia is oxidized to hydroxylamine. ...
Due to the growing costs of agricultural production and the need to protect the environment, there has been a need to intensify activities leading to an increase in the effectiveness of natural biological processes. These measures should increase the biodiversity of the environment, enable the adaptation of microorganisms and the protection of plants and soils against the background of the concept of sustainable agricultural development. The soil is an important environment in which many elements are transformed, including nitrogen necessary for the proper yielding of plants. The aim of the article is to present the microbiological aspect of nitrogen transformation, starting with a review of historical findings and then to discuss the progress of the latest developments that have contributed to a detailed understanding of the biochemical reactions occurring during nitrogen transformation in soil. Moreover, the aim of the study is to present the current state of knowledge on the dynamics of nitrogen uptake and conversion by various species of microorganisms and the relationship between the activity of nitrogen microorganisms and nitrogen uptake by plants. The article also includes the latest information on the possibility of using microbiological biostimulants supporting plant growth (PGPR) and protection against the effects of phytopathogens.
The explosive expansion of human activity during the last two centuries through industrial and agricultural pursuits has resulted in massive changes in the nitrogen (N) cycle of the planet. Based on the projected population growth and food demand, the N-fertilizer inputs into agricultural systems need to be doubled in the near future which would lead to further increase in the amount of N lost to the environment. If production agriculture continues to move towards high-nitrification agricultural systems with the expansion and intensification of agricultural activities, there is potential for catastrophic consequences to our planet due to the destruction of the ozone layer, global warming, and eutrophication. It is therefore imperative to manage the nitrification in agricultural systems for minimizing N leaks into the environment which are not only a serious economic and energy drain on society but also potentially have long-term ecological and environmental consequences. Currently, more than 60 % of the total N applied to agricultural systems is lost, amounting to an annual economic loss equivalent to US$17 billion worldwide. Wide substrate range of ammonia monooxygenase (AMO), an important enzyme involved in nitrification, has enabled a range of chemicals or chemical formulations that can be effectively deployed as additives to N fertilizers to regulate nitrification. These chemicals by augmenting the efficiency of N-fertilizer use help us to achieve higher food production for catering the ever increasing population and minimize fertilizer-related pollution of the environment. This paper overviews N transformations in agricultural systems and the salient agrochemicals employed for management of nitrification, the most important transformation, in particular.
Research was completed on the behaviour and fate of tetrabromobisphenol A (TBBPA) in pilot-scale membrane bioreactors and conventional activated sludge (CAS) process at the City of Guelph Wastewater Treatment Plant. Emphasis was on the physicochemical processes, biological transformation and sorption kinetics. Measurement of TBBPA at the environmental level can be challenging, so the main focus of this paper was the development of an analytical method for the nano-level determination of TBBPA. The approach used was gas chromatography-negative ion chemical ionization-mass spectrometry in select ion monitoring mode. For the wastewater matrix studied, the developed method had a low method detection level (MDL) of 2.4 ng/L. The matrix effects for influent and activated sludge mixed liquor were determined to be 36.5±5.9% (n ¼ 10) and 79.2± 4.5% (n ¼ 10), respectively. Preliminary results show that the CAS system demonstrates better performance for TBBPA removal, with removal at 83%. This was corroborated by the batch experiments that showed that the synergistic effects of biodegradation and biosorption potentially provide more removal of the TBBPA through the activated sludge process.
This research investigates a novel approach to methanol production from methane. The high use of fossil fuels in New Zealand and around the world causes global warming. Using clearer, renewable fuels the problem could potentially be reduced. Biomass energy is energy stored in organic matter such as plants and animals and is one of the options for a cleaner, renewable energy source. A common biofuel is methane that is produced by anaerobic digestion. Although methane is a good fuel, the energy is more accessible if it is converted to methanol. While technology exists to produce methanol from methane, these processes are thermo-chemical and require large scale production to be economic. Nitrosomonas europaea, a nitrifying bacterium, has been shown to oxidize methane to methanol (Hyman and Wood 1983). This research investigates the possibility of converting methane into methanol using immobilized N. europaea for use in smaller applications. A trickle bed bioreactor was developed, containing a pure culture of N. europaea immobilized in a biofilm on ceramic raschig rings. The reactor had a biomass concentration of 7.82 ± 0.43 g VSS/l. This was between 4 – 15 times higher than other systems aimed at biologically producing methanol. However, the immobilization dramatically affected the methanol production ability of the cells. Methanol was shown to be produced by the immobilized cells with a maximum production activity of 0.12 ± 0.08 mmol/gVSS.hr. This activity was much lower than the typical reported value of 1.0 mmol/g dry weight.hr (Hyman and Wood 1983). The maximum methanol concentration achieved in this system was 0.129 ± 0.102 mM, significantly lower than previous reported values, ranging between 0.6 mM and 2 mM (Chapman, Gostomski, and Thiele 2004). The results also showed that the addition of methane had an effect on the energy gaining metabolism (ammonia oxidation) of the bacteria, reducing the ammonia oxidation capacity by up to 70%. It was concluded, because of the low methanol production activity and the low methanol concentrations produced, that this system was not suitable for a methanol biosynthesis process.
The overall goal of this study was to develop an appropriate biological process for achieving autotrophic conversion of methane (CH4) to methanol (CH3OH). In this study, we employed ammonia oxidizing bacteria (AOB) to selectively and partially oxidize CH4 to CH3OH. In fed-batch reactors using mixed nitrifying enrichment cultures from a continuous bioreactor, up to 59.89 ± 1.12 mg COD/L of CH3OH was produced within an incubation time of 7 h, which is approximately ten times the yield obtained previously using pure cultures of Nitrosomonas europaea. The maximum specific rate of CH4 to CH3OH conversion obtained during this study was 0.82 mg CH3OH COD/mg AOB biomass COD-d, which is 1.5 times the highest value reported with pure cultures. Notwithstanding these positive results, CH4 oxidation to CH3OH by AOB was inhibited by NH3 (the primary substrate for the oxidative enzyme, ammonia monooxygenase, AMO) as well as the product, CH3OH, itself. Further, oxidation of CH4 to CH3OH by AOB was also limited by reducing equivalents supply, which could be overcome by externally supplying hydroxylamine (NH2OH) as an electron donor. Therefore, a potential optimum design for promoting CH4 to CH3OH oxidation by AOB could involve supplying NH3 (needed to maintain AMO activity) uncoupled from the supply of NH2OH and CH4. Partial oxidation of CH4 containing gases to CH3OH by AOB represents an attractive platform for the conversion of a gaseous mixture to an aqueous compound, which could be used as a commodity chemical. Alternately, the nitrate and CH3 OH thus produced could be channeled to a downstream anoxic zone in a biological nitrogen removal process to effect nitrate reduction to N2, using an internally produced organic electron donor.
Diverse aerobic and anaerobic microorganisms have the ability to degrade selected atmospheric halocarbons. In many cases,
these degradative reactions are operative at the ambient tropospheric mixing ratios of these substances. This will either
result in their complete destruction, or in the accumulation of non-degradable (and perhaps toxic) intermediates within aquatic
and terrestrial ecosystems. The significance of these microbiological sinks with respect to the global biogeochemical budgets
of halocarbons has not been accurately assessed. However, preliminary results suggest that they depend on the particular compound
in question. Thus, biodegradation appears to be a minor global sink for certain CFCs while for methyl halides it is a major
one. A challenge for future research, therefore, is not only to define novel pathways and microorganisms, but also to determine
if these reactions truly represent important biogeochemical sinks.
Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four strains of autotrophic ammonia-oxidizing
bacteria (AOB) are reported. TwoNitrosospira strains were considerably more sensitive to LAS than two Nitrosomonas strains were. Interestingly, the two Nitrosospira strains showed a weak capacity to remove LAS from the medium. This could not be attributed to adsorption or any other known
physical or chemical process, suggesting that biodegradation of LAS took place. In each strain, the metabolic activity (50%
effective concentration [EC50], 6 to 38 mg liter−1) was affected much less by LAS than the growth rate and viability (EC50, 3 to 14 mg liter−1) were. However, at LAS levels that inhibited growth, metabolic activity took place only for 1 to 5 days, after which metabolic
activity also ceased. The potential for adaptation to LAS exposure was investigated with Nitrosomonas europaea grown at a sublethal LAS level (10 mg liter−1); compared to control cells, preexposed cells showed severely affected cell functions (cessation of growth, loss of viability,
and reduced NH4
+ oxidation activity), demonstrating that long-term incubation at sublethal LAS levels was also detrimental. Our data strongly
suggest that AOB are more sensitive to LAS than most heterotrophic bacteria are, and we hypothesize that thermodynamic constraints
make AOB more susceptible to surfactant-induced stress than heterotrophic bacteria are. We further suggest that AOB may comprise
a sensitive indicator group which can be used to determine the impact of LAS on microbial communities.
A marine methylotroph, designated strain MB2T, was isolated for its ability to grow on methyl bromide as a sole carbon and energy source. Methyl chloride and methyl iodide also supported growth, as did methionine and glycine betaine. A limited amount of growth was observed with dimethyl sulfide. Growth was also noted with unidentified components of the complex media marine broth 2216, yeast extract and Casamino acids. No growth was observed on methylated amines, methanol, formate, acetate, glucose or a variety of other substrates. Growth on methyl bromide and methyl iodide resulted in their oxidation to CO2 with stoichiometric release of bromide and iodide, respectively. Strain MB2T exhibited growth optima at NaCl and Mg2+ concentrations similar to that of seawater. Phylogenetic analysis of the 16S rDNA sequence placed this strain in the alpha-Proteobacteria in proximity to the genera Ruegeria and Roseobacter. It is proposed that strain MB2T (= ATCC BAA-92T = DSM 14336T) be designated Leisingera methylohalidivorans gen. nov., sp. nov..
Although cooxidative biodegradation of monohalogenated hydrocarbons has been well studied in the model NH(3)-oxidizing bacterium, Nitrosomonas europaea, virtually no information exists about cooxidation of these compounds by native populations of NH(3)-oxidizing bacteria. To address this subject, nitrifying activity was stimulated to 125-400 nmol NO(3)(-) produced g(-1) soil h(-1) by first incubating a Ca(OH)(2)-amended, silt loam soil (pH 7.0+/-0.2) at field capacity (270 g H(2)O kg(-1) soil) with 10 micro mol NH(4)(+) g(-1) soil for 14 days, followed by another 10 days of incubation in a shaken slurry (2:1 water:soil, v/w) with periodic pH adjustment and maintenance of 10 mM NH(4)(+). These slurries actively degraded both methyl bromide (MeBr) and ethyl chloride (EtCl) at maximum rates of 20-30 nmol ml(-1) h(-1) that could be sustained for approximately 12 h. Although the MeBr degradation rates were linear for the first 10-12 h of incubation, they could not be sustained regardless of NH(4)(+) level and declined to zero over 20 h of incubation. The transformation capacity of the slurry enrichments (~1 micro mol MeBr ml(-1) soil slurry) was similar to the value measured previously in cell suspensions of N. europaea with similar NH(3)-oxidizing activity. Several MeBr-degrading characteristics of the nitrifying enrichments were found to be similar to those documented in the literature for MeBr-degrading methanotrophs and facultatively methylotrophic bacteria.
