Nitrification Nitrosomonas

Flnoromethane has been nsed as a selective inhibitor of ammoninm oxidation and nitrification-linked synthesis of N2O in Nitrosomonas europaea (Miller et al.l993), while difluoromethane has been proposed as a reversible inhibitor of methanotrophs (Miller et al. 1998). 

Aerobic The reactions carried out by Nitrosomonas and Nitrobacter (reactions b and c, autotrophic respectively) are known as nitrification, while those carried out by Beggiatoa and Thiobacillus thiooxidans (reactions d and e, respectively) are examples of sulfur oxidation ... 

Konig et al. [80-84] demonstrated that microbial sensors are suitable for the summary quantification of nitrifiable compounds (see also Sect. 3.3.1) as well as for the detection of nitrification inhibiting effects. Such biosensors, which contain a mixed population of the nitrifying bacteria Nitrosomonas sp. and Nitrobacter sp., exhibit a specific supplementary metabolic capacity. This enables the amperometric determination of ammonia according the following scheme of nitrification ... 

For the most part, nitrification involves the activity of two very different classes of bacteria (Wallace and Nicholas, 1969 Kuenen and Robertson, 1987). The first step, the 6-electron oxidation of NH, to nitrite (NO2 ), is carried out by a small numbet of genera of autotrophic bacteria, exemplified by Nitrosomonas the second step, the 2-electron oxidation of nitrite to nitrate (NO3 ) by a sim-... 

The oxidation of ammonia to nitrite, in the process of nitrification, is brought about mainly by autotrophic bacteria such as Nitrosomonas species. The oxidation of nitrite to nitrate is due to the action of Nitrobacter species. 

Nitrification. In biological nitrification ammonium nitrogen is oxidized into nitrite by means of Nitrosomonas species, and nitrite is oxidized to nitrate by the Nitrobacter species. 

Nitrification is carried out by unique specialized bacteria in a two-step reaction. The first step, oxidation of ammonium (NH4) to nitrite (NOp, is catalyzed by a few species of bacteria that have names beginning with nitroso-, for example, nitrosomonas and nitrosospira. The reaction is as follows ... 

Based on Reactions 8.14 and 8.15, nitrification is energetically favorable (overall AG° = -84 kcal). The intermediate nitrogen form, NO , rarely accumulates in significant concentrations because nictrobacter normally acts as fast or faster than the N02-producing bacteria. However, nitrobacter is more sensitive to ammonia than nitrosomonas, and for this reason nitrite may accumulate under high concentrations of NH (Fig. 8.5) but not under low concentrations of NH4 (Fig. 8.6)... 

Various soil processes also contribute to soil acidity. Decaying organic matter releases a number of organic acids, as indeed do plant roots. Nitrification, the microbial oxidation of ammonium ions to nitrate by Nitrosomonas and Nitrobacter, occurs in slightly acidic to neutral soils and releases H" " ions ... 

The reactions in the nitrification process are mediated by two types of autotrophic bacteria Nitrosomonas and Nitrobacter. The ammonia comes from the nitrogen content of any organic substance, such as proteins, that contains about 16% nitrogen. As soon as the ammonia has been hydrolyzed from the organic substance, Nitrosomonas consumes it and in the process also consumes oxygen according to... 

The Nitrosomonas and the Nitrobacter reactions may now be added to produce the overall nitrification reaction as shown next. 

Based partly on anecdotal evidence from culture work, observations in waste water treatment systems with very high particulate loads, the tendency of nitrifiers to grow in aggregates in bioreactor biofilms, and the prevalence of small particles in natural waters, it has been suggested that nitrification occurs mainly on particles and is mediated by particle-attached bacteria (Hagopian and Riley, 1998). Nitrifier sequences were found both associated with particles and in the bulk seawater phase in the northwestern Mediterranean Sea. In the clone library of 16S rRNA sequences, Nitrosomonas-like sequences were preferentially associated with particles and Nitrosospira-]ike sequences dominated in clones from the planktonic phase (PhiUips et al, 1999). This may indicate niche preference by the different groups on the basis of attachment to particles, substrate concentration or other physical/... 

Zart, D., and Bock, E. (1998). High rate of aerobic nitrification and denitrification by Nitrosomonas eutropha grown in a fermentor with complete biomass retention in the presence of gaseous NO2 or NO. Archives of Microbiology 169, 282—286. 

---