Inhibition of Bacterial Ammonia Oxidation by Organohydrazines in Soil Microcosms

Abstract

Hydroxylamine oxidation by hydroxylamine oxidoreductase (HAO) is a key step for energy-yielding in support of the growth of ammonia-oxidizing bacteria (AOB). Organohydrazines have been shown to inactivate HAO from Nitrosomonas europaea, and may serve as selective inhibitors to differentiate bacterial from archaeal ammonia oxidation due to the absence of bacterial HAO gene homolog in known ammonia-oxidizing archaea (AOA). In this study, the effects of three organohydrazines on activity, abundance, and composition of AOB and AOA were evaluated in soil microcosms. The results indicate that phenylhydrazine and methylhydrazine at the concentration of 100 μmol g−1 dry weight soil completely suppressed the activity of soil nitrification. Denaturing gradient gel electrophoresis fingerprinting and sequencing analysis of bacterial ammonia monooxygenase subunit A gene (amoA) clearly demonstrated that nitrification activity change is well paralleled with the growth of Nitrosomonas europaea-like AOB in soil microcosms. No significant correlation between AOA community structure and nitrification activity was observed among all treatments during the incubation period, although incomplete inhibition of nitrification activity occurred in 2-hydroxyethylhydrazine-amended soil microcosms. These findings show that the HAO-targeted organohydrazines can effectively inhibit bacterial nitrification in soil, and the mechanism of organohydrazine affecting AOA remains unclear.

Comparison of the Effects of Phenylhydrazine Hydrochloride and Dicyandiamide on Ammonia-Oxidizing Bacteria and Archaea in Andosols

“…Both PHH and DCD had limited effect on the community structure of AOB and no effect on the community structure of AOA. Based on our observation and a previous report ( Wu et al, 2012 ), PHH appears to have toxic effects on archaea although archaea lack hao ; thus, further studies are required to understand the mechanism underlying this phenomenon and to develop organohydrazine-based NIs targeting HAO.…”

“…Compared with the Control samples, a significantly lower abundance of AOB amoA was observed in the presence of DCD and PHH from days 6 to 14 ( Figure 2A ), indicating similar dynamics between the AOB population and the net nitrification rate ( Aarnio and Martikainen, 1992 ; Patra et al, 2006 ; Schauss et al, 2009 ; Di and Cameron, 2011 ; Wu et al, 2012 ; Liu et al, 2014 ). The inhibitory effect of PHH and DCD on AOA was similar to that observed in AOB.…”

“…Thus, if nitrification is inhibited because of the inactivation of HAO, the nitrification activity of AOA should not be affected. A recent report revealed that soil nitrification was completely suppressed by high concentration of organohydrazines (100 mmol⋅kg -1 soil) and correlated well with the AOB rather than AOA community structure ( Wu et al, 2012 ). Thus, organohydrazines have considerable potential for the development of next-generation NIs targeting HAO ( Nishigaya et al, 2016 ), even though most commercially available NIs target AMO.…”

Deammonification process start-up after enrichment of anammox microorganisms from reject water in a moving-bed biofilm reactor

“…Similarly to [12], organohydrazines at the concentration of 100 μmol g −1 dry weight soil nearly completely suppressed the soil NOB instead of AOB and ammonium oxidizing arhaea, latter have been shown to be tolerant to N 2 H 4 concentrations as they do not have HAO which hydrazine affects. Within 335-400 days, N 2 H 4 concentration increased from 14 to 150 μg N L −1 (NH 2 OH increased 30-50 μg N L −1 ), synchronously with the TN removal rate.…”

“…[9] Spiked addition of FA [9] into the reactor could more effectively diminish NOB activity than continuous feeding with high NH + 4 concentration. [11,12] The research question is whether the start-up period can be shortened by a better NOB control through first cultivating anammox biomass without the nitritation step and subsequently adding the aerobic treatment step. [10] In the deammonification via intermittent aeration in biofilm system, there has not yet been reported increased anammox intermediate N 2 H 4 concentration correlation with both increased TN removal and a decreased NO − 3 production rate for using it as a monitoring parameter.…”