Inhibition and Stimulation of Nitrification by Potassium Ethyl Xanthate

Underhill, S E; Prosser, James I.

doi:10.1099/00221287-133-11-3237

Cited by 4 publications

(3 citation statements)

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“…He concluded that restriction to penetration of inhibitors did not offer a general explanation for reduced sensitivity and suggested that biofilm cells existed in a different physiological state making them less susceptible. Exponentially growing populations of freely suspended ammonia oxidizers have been shown to be more sensitive to nitrapyrin than stationary phase cells [ 10], and ammonialimited cells are actually stimulated by concentrations of potassium ethyl xanthate that inhibit cells in the presence of excess substrate [ 14]. In terms of~No2, established biofilms grew much more slowly than freely suspended cells, as has been found in other studies of attached ammonia oxidizer populations [1,11].…”

Section: Discussionsupporting

confidence: 58%

Inhibition of biofilm populations of Nitrosomonas europaea

Powell

Prosser

1992

Microb Ecol

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The influence of surface attachment and growth on inhibition of the ammonia oxidizing bacterium, Nitrosomonas europaea, by nitrapyrin was investigated in liquid culture in the presence and absence of glass slides. Significant attachment to glass slides occurred in the absence of ammonia, but the extent of attachment was not affected by nitrapyrin, nor by previous culture of cells in medium containing nitrapyrin. The presence of glass slides affected neither the specific growth rate of N. europaea, measured by changes in nitrite concentration, nor inhibition by nitrapyrin. Inhibitory effects of nitrapyrin on increases in nitrite concentration and in free cell concentration were similar, but greater effects were observed on changes in attached cell concentration. Established biofilms on glass slides grew at a lower specific growth rate than freely suspended cells. Both biofilm cells, and those detached from the biofilm, were protected from inhibition. A mechanism for protection of biofilm populations is proposed involving reduced sensitivity of slowly growing cells producing extracellular polymeric material.

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Section: Discussionsupporting

confidence: 58%

Inhibition of biofilm populations of Nitrosomonas europaea

Powell

Prosser

1992

Microb Ecol

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“…AMO activity in whole cells is sensitive to copper-selective chelating agents, including allylthiourea (14,15,32,33), xanthates (52,53), carbon disulfide (21), ct, ao'-dipyridyl (15), and cyanide (15). Light is also a potent and specific inactivator of AMO (16,42).…”

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confidence: 99%

In vitro activation of ammonia monooxygenase from Nitrosomonas europaea by copper

1993

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The effect of copper on the in vivo and in vitro activity of ammonia monooxygenase (AMO) from the nitrifying bacterium Nitrosomonas europaea was investigated. The addition of CuCl2 to cell extracts resulted in 5-to 15-fold stimulation of ammonia-dependent 02 consumption, ammonia-dependent nitrite production, and hydrazine-dependent ethane oxidation. AMO activity was further stimulated in vitro by the presence of stabilizing agents, including serum albumins, spermine, or MgCl2. In contrast, the addition of CuCl2 and stabilizing agents to whole-cell suspensions did not result in any stimulation of AMO activity. The use of the AMO-specific suicide substrate acetylene revealed two populations of AMO in cell extracts. The low, copper-independent (residual) AMO activity was completely inactivated by acetylene in the absence of exogenously added copper. In contrast, the copper-dependent (activable) AMO activity was protected against acetylene inactivation in the absence of copper. However, in the presence of copper both populations of AMO were inactivated by acetylene. ['4Clacetylene labelling of the 27-kDa polypeptide of AMO revealed the same extent of label incorporation in both whole cells and optimally copper-stimulated cell extracts. In the absence of copper, the label incorporation in cell extracts was proportional to the level of residual AMO activity. Other metal ions tested, including Zn2+, Co2+, Ni2+, Fe2+, Fe3+, Ca2+, Mg2+, Mn2+, Cr3+, and Ag+, were ineffective at stimulating AMO activity or facilitating the incorporation of 14C label from [14C]acetylene into the 27-kDa polypeptide. On the basis of these results, we propose that loss of AMO activity upon lysis of N.europaea results from the loss of copper from AMO, generating a catalytically inactive, yet stable and activable, form of the enzyme.The chemolithoautotrophic ammonia-oxidizing bacterium Nitrosomonas europaea obtains all of its energy for growth from the oxidation of ammonia to nitrite (55). The initial oxidation of ammonia, which yields hydroxylamine as the product, is a reductant-and 02-dependent reaction catalyzed by ammonia monooxygenase (AMO):NH3 + 02 + 2e-+ 2H+ --NH20H + H20(1)Hydroxylamine is further oxidized to nitrite by hydroxylamine oxidoreductase (HAO):Two of the four electrons generated from hydroxylamine oxidation are used to support the oxidation of additional ammonia molecules, while the other two electrons enter the electron transfer chain and are used to support CO2 reduction and ATP biosynthesis (55). Despite the key role AMO plays in initiating biological nitrification, the enzyme has not been purified, and consequently, little is known about its structure, enzymatic mechanism, or the identity and function of its cofactors. This can be largely attributed to the difficulty of working with and assaying the enzyme in cell-free systems. The most convenient assays for measuring AMO activity are to monitor ammonia-dependent 02 consumption or nitrite production.These assays require a high degree of coupling: the hydroxylamine forme...

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“…Beyond the anecdotal nature of this discovery, the significance of the potent effects of CS2 on nitrification is perhaps more widespread than is generally appreciated, since the action of many other compounds that inhibit nitrification can also potentially be rationalized in terms of the mode of action of CS2. These inhibitory compounds include thiosulfates (18), thiocarbonates (1, 2), thiocarbamates (12,18), xanthates (such as potassium ethylxanthate) (18,29,30), sulfur-containing amino acids such 4776 HYMAN ET AL.…”

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confidence: 99%

Inhibition of ammonia monooxygenase in Nitrosomonas europaea by carbon disulfide

1990

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Carbon disulfide has long been recognized as a potent inhibitor of nitrification, and it is the likely active component in several nitrification inhibitors suitable for field use. The effects of this compound on Nitrosomonas europaea have been investigated, and the site of action has been determined. Low concentrations of CS2 (<400 ,uM) produced a time-dependent inhibition of ammonia-dependent O2 uptake but did not inhibit hydrazineoxidizing activity. CS2 also produced distinct changes in difference spectra of whole cells. These results suggest that ammonia monooxygenase (AMO) is the site of action of CS2. Unlike the case for thiourea and acetylene, saturating concentrations of CS2 did not fully inhibit AMO, and the inhibition resulted in a low but significant rate of ammonia-dependent 02 uptake. The effects of CS2 were not competitive with respect to ammonia concentration, and the inhibition by CS2 did not require the turnover of AMO to take effect. The ability of CS2-treated cells to incorporate [14C]acetylene into the 28-kilodalton polypeptide of AMO was used to demonstrate that the effects of CS2 are compatible with a mode of action which involves a reduction of the rate of turnover of AMO without effects on the catalytic mechanism. It is proposed that CS2 may act on AMO by reversibly reacting with a suitable nucleophilic amino acid in close proximity to the active site copper.The major process in microbial nitrification is the oxidation of ammonia to nitrite, followed by the oxidation of nitrite to nitrate. These reactions are predominantly catalyzed by specialized autotrophic bacteria characterized by such species as the ammonia-oxidizing bacterium Nitrosomonas europaea and the nitrite-oxidizing bacterium Nitrobacter winogradskyi, respectively. Although our understanding of the biochemistry and enzymology of individual reactions in the nitrification process is far from complete, there is a considerable general interest in nitrification because it plays an important role in controlling the balance between fixed and mobile forms of nitrogen in soil and water systems. For example, in agriculture, nitrification can lead to substantial losses of costly ammonia-based fertilizer (and urea-based fertilizer, which hydrolyzes to ammonia) because both nitrification products, nitrite and nitrate, are easily leached from soils by water. In addition, nitrate is the major substrate for denitrifying bacteria that generate gaseous products (N20, NO, and N2) which are lost to the atmosphere. These same reactions, while detrimental to agriculture, are regarded as positive benefits in water treatment regimens, in which the objective is to reduce the nitrogen content of waste waters (22).Because it is ammonia-oxidizing bacteria that initiate nitrification as a whole, there has been considerable research into the inhibition of this process. Ammonia oxidation by N. europaea is a two-stage process that is now thought to involve the initial oxidation of ammonia to hydroxylamine by a membrane-bound enzyme known as ammonia monooxyge...

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Inhibition and Stimulation of Nitrification by Potassium Ethyl Xanthate

Cited by 4 publications

References 14 publications

Inhibition of biofilm populations of Nitrosomonas europaea

Inhibition of biofilm populations of Nitrosomonas europaea

In vitro activation of ammonia monooxygenase from Nitrosomonas europaea by copper

Inhibition of ammonia monooxygenase in Nitrosomonas europaea by carbon disulfide

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