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PubMed2003

Chemolithoorganotrophic growth of Nitrosomonas europaea on fructose.

The nitrifying bacterium Nitrosomonas europaea can obtain all its carbon for growth from CO(2) and all its energy and reductant for growth from the oxidation of NH(3) and is considered an obligate chemolithoautotroph. Previous studies have shown that N. europaea can utilize limited amounts of certain organic compounds, including amino acids, pyruvate, and acetate, although no organic compound has been reported to support the growth of N. europaea. The recently completed genomic sequence of N. europaea revealed a potential permease for fructose. With this in mind, we tested if N. europaea could utilize fructose and other compounds as carbon sources to support growth. Cultures were incubated in the presence of fructose or other organic compounds in sealed bottles purged of CO(2). In these cultures, addition of either fructose or pyruvate as the sole carbon source resulted in a two- to threefold increase in optical density and protein content in 3 to 4 days. Studies with [(14)C]fructose showed that >90% of the carbon incorporated by the cells during growth was derived from fructose. Cultures containing mannose, glucose, glycerol, mannitol, citrate, or acetate showed little or no growth. N. europaea was not able to grow with fructose as an energy source, although the presence of fructose did provide an energy benefit to the cells. These results show that N. europaea can be grown in CO(2)-free medium by using fructose and pyruvate as carbon sources and may now be considered a facultative chemolithoorganotroph.

Fructose↗
PubMed2003

Excision and integration of cassettes by an integron integrase of Nitrosomonas europaea.

We found in the environmental strain Nitrosomonas europaea a chromosomal integron-like structure with an integrase gene, intI(Neu). We have tested the capacity of the IntINeu integrase to excise and integrate several resistance gene cassettes. The results allow us to consider IntINeu a new functional integron integrase.

Attachment Sites, Microbiological↗
PubMed2004

Nitrosomonas europaea expresses a nitric oxide reductase during nitrification.

In this paper, we report the identification of a norCBQD gene cluster that encodes a functional nitric oxide reductase (Nor) in Nitrosomonas europaea. Disruption of the norB gene resulted in a strongly diminished nitric oxide (NO) consumption by cells and membrane protein fractions, which was restored by the introduction of an intact norCBQD gene cluster in trans. NorB-deficient cells produced amounts of nitrous oxide (N2O) equal to that of wild-type cells. NorCB-dependent activity was present during aerobic growth and was not affected by the inactivation of the putative fnr gene. The findings demonstrate the presence of an alternative site of N2O production in N. europaea.

Multigene Family↗
PubMed2004

Physiologic and proteomic evidence for a role of nitric oxide in biofilm formation by Nitrosomonas europaea and other ammonia oxidizers.

NO, a free radical gas, is the signal for Nitrosomonas europaea cells to switch between different growth modes. At an NO concentration of more than 30 ppm, biofilm formation by N. europaea was induced. NO concentrations below 5 ppm led to a reversal of the biofilm formation, and the numbers of motile and planktonic (motile-planktonic) cells increased. In a proteomics approach, the proteins expressed by N. europaea were identified. Comparison studies of the protein patterns of motile-planktonic and attached (biofilm) cells revealed several clear differences. Eleven proteins were found to be up or down regulated. Concentrations of other compounds such as ammonium, nitrite, and oxygen as well as different temperatures and pH values had no significant effect on the growth mode of and the proteins expressed by N. europaea.

Ammonia↗
PubMed2005

Novel nirK cluster genes in Nitrosomonas europaea are required for NirK-dependent tolerance to nitrite.

Nitrite reductase (NirK) of Nitrosomonas europaea confers tolerance to nitrite (NO2-). The nirK gene is clustered with three genes of unknown physiological function: ncgABC. At present, this organization is unique to nitrifying bacteria. Here we report that the ncgABC gene products facilitate NirK-dependent NO2- tolerance by reversing the negative physiological effect that is associated with the activity of NirK in their absence. We hypothesize that the ncg gene products are involved in the detoxification of nitric oxide that is produced by NirK.

Genes, Bacterial↗
PubMed2006

Disruption of sucA, which encodes the E1 subunit of alpha-ketoglutarate dehydrogenase, affects the survival of Nitrosomonas europaea in stationary phase.

Although Nitrosomonas europaea lacks measurable alpha-ketoglutarate dehydrogenase activity, the recent completion of the genome sequence revealed the presence of the genes encoding the enzyme. A knockout mutation was created in the sucA gene encoding the E1 subunit. Compared to wild-type cells, the mutant strain showed an accelerated loss of ammonia monooxygenase and hydroxylamine oxidoreductase activities upon entering stationary phase. In addition, unlike wild-type cells, the mutant strain showed a marked lag in the ability to resume growth in response to pH adjustments in late stationary phase.

Gene Expression Regulation, Bacterial↗
PubMed1967

Growth response of Nitrosomonas europaea to amino acids.

Growth responses of Nitrosomonas europaea to individual amino acids or vitamins was observed in log-phase cultures, as was the incorporation of carbon-14 labeled amino acids. Nitrite formation and protein synthesis were increased by l-glutamic acid, l-aspartic acid, l-serine, and l-glutamine. l-Lysine, l-histidine, l-threonine, l-valine, l-methionine, and l-arginine were inhibitory. The other amino acids had no effect on growth. All of the uniformly labeled amino acids added at low concentrations were taken up by growing cells and distributed into cell fractions. From 1 to 12% of the added radioactivity was present in cells analyzed in late log phase, depending on the amino acid; glycine and l-serine caused accumulation of the label to the greatest extent, whereas l-aspartic and l-glutamic acids were among those incorporated to the least extent. Aspartic acid increased both cell protein and nitrite values, but did not alter the ratio of protein to nitrite from that found in controls.

Amino Acids↗
PubMed1968

Purification and properties of peroxidase from Nitrosomonas europaea.

Peroxidase from the obligate chemosynthetic bacterium Nitrosomonas europaea was purified 1,500-fold, and its properties were examined. The enzyme had a molecular weight of 53,000 and exhibited characteristic absorption maxima at 410, 524, and 558 mmu. The optimal pH and temperature were 7.5 and 44 C, respectively. The peroxidase reaction had an energy of activation of 5,850 cal/mole and required a primary substrate (H(2)O(2)) concentration of 7 x 10(-6)m to proceed at half maximal velocity (K(m)). Reduced cytochrome, c,p-phenylenediamine and pyrogallol acted as hydrogen donors to the purified peroxidase-H(2)O(2) complex. Conditions most suitable for the chemical oxidation of ammonium by H(2)O(2) were determined. The reaction was rapid and produced nitrite but no nitrate. Hydroxylamine was not detected as an intermediate, but it could substitute for ammonium in the system. Neither the rate nor the extent of these reactions was influenced by purified peroxidase, and no evidence was obtained to support a conclusion that the enzyme performs a vital role in the transformation of ammonium to nitrite by N. europaea.

Chemistry Techniques, Analytical↗
PubMed1981

Cell-free ammonia-oxidizing system of Nitrosomonas europaea: general conditions and properties.

Conditions essential for the preparation of active ammonia-oxidizing extracts of Nitrosomonas europaea were studied. The extracts were unstable during storage and required specific assay conditions for ammonia oxidation. Bovine serum albumin, spermine, or MgCl2 was required for ammonia oxidation and the concentration of phosphate determined the relative effectiveness of each activator, i.e., albumin being most effective in 0.1 M phosphate and spermine or MgCl2 at lower phosphate concentrations. Kinetic experiments showed a partial reduction of cytochrome c preceding the initiation of oxygen consumption due to ammonia oxidation.

Ammonia↗
PubMed2000

Mutational analysis of the multicopy hao gene coding for hydroxylamine oxidoreductase in Nitrosomonas sp. strain ENI-11.

The ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11 contains three copies of the hao gene (hao1, hao2, and hao3) coding for hydroxylamine oxidoreductase (HAO). Three single mutants (hao1::kan, hao2::kan, or hao3::kan) had 68 to 75% of the wild-type growth rate and 58 to 89% of the wild-type HAO activity when grown under the same conditions. A double mutant (hao1::kan and hao3::amp) also had 68% of the wild-type growth and 37% of the wild-type HAO activity.

DNA Mutational Analysis↗
PubMed2002

Isolation and characterization of cbbL and cbbS genes encoding form I ribulose-1,5-bisphosphate carboxylase/oxygenase large and small subunits in Nitrosomonas sp. strain ENI-11.

The cbbL and cbbS genes encoding form I ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large and small subunits in the ammonia-oxidizing bacterium Nitrosomonas sp. strain ENI-11 were cloned and sequenced. The deduced gene products, CbbL and CbbS, had 93 and 87% identity with Thiobacillus intermedius CbbL and Nitrobacter winogradskyi CbbS, respectively. Expression of cbbL and cbbS in Escherichia coli led to the detection of RubisCO activity in the presence of 0.1 mM isopropyl-beta-D-thiogalactopyranoside (IPTG). To our knowledge, this is the first paper to report the genes involved in the carbon fixation reaction in chemolithotrophic ammonia-oxidizing bacteria.

Ammonia↗
PubMed2001

Conversion of ammonia to dinitrogen in wastewater by Nitrosomonas europaea.

Because Nitrosomonas europaea contains ammonia-oxidizing enzyme, nitrite reductase, and nitrous oxide reductase, the conversion of ammonia to dinitrogen was tried with different reaction conditions. In aerobic reaction conditions, ammonium was converted to nitrite (NO2-), while under oxygen-limiting or oxygen-free conditions, NO2(-)-N formed from ammonia oxidation by N. europaea was reduced to N2O and dinitrogen with 22% conversion. During denitrification, optimal pH for the production of N2O and dinitrogen was found to be 7.0-8.0. Dinitrogen was not produced in acidic pH <7.0. A low partial oxygen pressure as well as oxygen-free conditions are favorable for high production of dinitrogen.

Ammonia↗
PubMedDate not supplied

Quantification of Nitrosomonas oligotropha and Nitrospira spp. using competitive polymerase chain reaction in bench-scale wastewater treatment reactors operating at different solids retention times.

The effect of solids retention time (SRT) on ammonia-and nitrite-oxidizing bacteria was measured by Nitrosomonas oligotropha-like ammonia monooxygenase A and Nitrospira 16S rDNA competitive polymerase chain reaction assays in a complete-mix, bench-scale, activated-sludge system. During steady-state operation, nitrification was complete in the 20- and 10-day SRT reactors, nearly complete in the 5-day SRT reactor, and incomplete in the 2-day SRT reactor (76% ammonia oxidation and 85% nitrite oxidation). Total microbes, measured by dot-blot hybridizations, ranged from 3 x 10(11) to 3 x 10(12) cells/L, and increased with increasing SRTs. The concentration of the ammonia-oxidizer N. oligotropha dropped 100-fold from the 20-day SRT (5 x 10(9) cells/L) to the 2-day SRT (< or = 4 x 10(7) cells/L). Thus, N. oligotropha became a much smaller fraction of the total biomass in the poorly performing 2-day SRT reactor. The concentration of Nitrospira cells also decreased (10-fold) as the SRT was reduced from 20 days to 2 days. However, the number of Nitrospira cells was always greater than the number of N. oligotropha cells measured in each reactor (10- to 60-fold). While Nitrospira comprised 1 to 2% of the biomass, N. oligotropha represented only 0.04 to 0.27% of the total population. This low percentage suggests that N. oligotropha was not a dominant ammonia oxidizer in the bench-scale systems.

Ammonia↗
PubMed2003

[Preliminary study of characteristics of a special Nitrosomonas].

A special obligately-autotrophic Nitrosomonas was isolated from high temperature and hypersaline drainage water obtained off a wastewater treatment plant. It was Gram-negative, nonsporulating, ellipsoidal or short-rod shaped bacterium that singly arranged or arranged in a circle or in a row. Cells were 0.7 to 0.9 microm wide and 1.2 to 1.98 microm long. Electron-microscopic scanning of these cells indicated that they were wrapped by unknown fluff-like matter. They oxidized ammonium to nitrite and caused the removal of nitrogen from the system. But the decrease of NH4+ -N did not accord with the increase of NO2 - -N and NO3- -N was almost not detected. After 12 d of cultivation at 50 degrees C, about 10% of the NH4+ -N was converted to NO2- -N, 15% remained as NH4+ -N, and the other 75% was removed from the system, including 17% of NH4+ -N volatilized.

Nitrites↗
PubMed1992

14C2H2- and 14CO2-labeling studies of the de novo synthesis of polypeptides by Nitrosomonas europaea during recovery from acetylene and light inactivation of ammonia monooxygenase.

Incubation of cells of the nitrifying bacterium Nitrosomonas europaea with 14C2H2 results in the covalent attachment of 14C label to a membrane-bound polypeptide of an approximate Mr of 28,000 (Hyman, M.R., and Wood, P.M. (1985) Biochem. J. 227, 719-725). A labeling procedure using 14C2H2 generated from Ba14CO3 has been used to investigate the correlation between the extent of covalent modification of this polypeptide by 14C from 14C2H2 and the level of ammonia oxidizing activity in whole cells. The time-dependent inactivation of ammonia monooxygenase by 14C2H2 resulted in a progressive and saturable incorporation of 14C into a 27-kDa polypeptide. In contrast, the specific, time-dependent and complete inactivation of ammonia monooxygenase by light resulted in concomitant decrease in the ability of cells to incorporate 14C from 14C2H2 into this polypeptide. The 14C2H2 labeling procedure was also used to investigate the recovery of ammonia monooxygenase activity after complete inactivation of pre-existing ammonia monooxygenase by either C2H2 or light. The recovery of ammonia monooxygenase activity was closely correlated with a recovery of ability of cells to incorporate 14C label from 14C2H2 into the 27-kDa polypeptide. This recovery process was energy (NH4+)-dependent and was inhibited by chloramphenicol and rifampicin, implying that de novo protein synthesis was required. Additional polypeptides labeled with 14C from 14CO2 were also identified during recovery from C2H2 or light inactivation of ammonia monooxygenase.

Acetylene↗
PubMed1986

Tetraheme cytochrome c-554 from Nitrosomonas europaea. Heme-heme interactions and ligand binding.

Cytochrome c-554 functions in the ammonia oxidizing system of Nitrosomonas europaea. We have investigated its molecular and ligand binding properties and studied the protein with optical, EPR, and Mössbauer spectroscopies in the pH range from 2 to 13. Amino acid, heme, and metal analyses show that the protein has Mr = 25,000 and that it contains four c-type hemes per molecule. Optical spectra reveal that the heme ligand structures are sensitive to the pH of the medium and that the hemes can bind small molecules such as CN-, CO, and NO under certain conditions. According to the Mössbauer and EPR studies of the ferric protein, the hemes are predominantly (75%) high spin at pH 2 and low spin (approximately equal to 100%) above pH 10. At neutral pH, Mössbauer data show that 75% of the heme is low spin and that the remainder is high spin. The EPR data, however, do not reveal any signals attributable to typical high spin or low spin species. Rather, a very complex and unusual spectrum with a main feature at g = 3.3 is observed at X-band, this feature shifts to approximately g = 3 at S-band. The EPR and Mössbauer data show clearly that the hemes are magnetically interacting, by dipolar and exchange interactions. At pH 2, the EPR spectra reveal resonances at g = 6 and 2. The Mössbauer spectra prove that all hemes are magnetically coupled at this pH. Coupling is also borne out by the observation of a half-field EPR resonance near g = 12.

Amino Acids↗
PubMed1986

N-terminal amino acid sequence of cytochrome c-552 from Nitrosomonas europaea.

Nitrosomonas europaea is an ammonia-oxidizing bacterium which contains multiple c-type cytochromes. Few of these components have been assigned physiological roles, but on the basis of molecular weight and redox potential cytochrome c-552 has been considered to be an analogue of the mitochondrial cytochrome-c family of proteins. We present the N-terminal amino acid sequence (47 residues) of cytochrome c-552 and show that this protein is most closely related to the group of small cytochrome-c components from pseudomonads (cytochromes c-551) and is probably evolutionarily distant from the analagous protein (cytochrome c-550) from the nitrite-oxidizing bacterium Nitrobacter agilis.

Amino Acid Sequence↗