Competition between two nitrite-oxidizing bacterial populations: a model for studying the impact of wastewater treatment plant discharge on nitrification in sediment

Abstract

Nitrobacter, a ubiquitous nitrite oxidizer in natural and anthropized environments, is commonly studied as the model genus performing the second stage of nitrification. In rivers, wastewater treatment plant discharges may affect the nitrite-oxidizing activity and the responsible genera that are largely associated with sediment. We used a laboratory batch culture approach with Nitrobacter wynogradskyi ssp. agilis strain AG and Nitrobacter hamburgensis strain X(14) to characterize the possible stress effect of wastewater effluent on these populations and to study the possible competition between an effluent strain (X(14)) and a sediment strain (AG) over a 42-day incubation time. Immunofluorescence enumerations of each strain showed that they both survived and settled in the sediment, indicating that there was no significant stress effect due to chemical changes caused by the effluent. The development of the strains' density and activity was directly correlated with the available nitrite concentration. Nevertheless, the potential specific activity was not constant along the so-called mixotrophic (non-limiting nitrite concentration) and heterotrophic (nitrite depletion) conditions. This illustrates the inducibility of the nitrite oxidoreductase and indicates the metabolic versatility of the strains. In our experimental conditions, the preferentially autotrophic AG strain appeared more competitive than the preferentially mixo- or heterotrophic X(14) strain, including in heterotrophic environment.

Shifts between Nitrospira‐ and Nitrobacter‐like nitrite oxidizers underlie the response of soil potential nitrite oxidation to changes in tillage practices

“…The key role of mineral N supply for understanding the response of PNO to tillage practices in agricultural soils is consistent with the strong correlation between the activity of two Nitrobacter strains and NO 2 ‐ concentrations observed in batch cultures (Feray and Montuelle, 2002). Similarly, in microcosms of sterile soils inoculated with Nitrobacter strains, Degrange and colleagues (1997) have reported a strong increase in PNO after NO 2 ‐ supply, whereas the supply of organic carbon had a weaker effect on NOB activity.…”

“…More generally, PNO has been reported to be related to Nitrobacter abundance in sterile soil microcosms inoculated with Nitrobacter strains (Degrange et al. , 1997), batch cultures of Nitrobacter strains (Feray and Montuelle, 2002) and river water (Cebron et al. , 2003).…”

“…from 200 to 1300 μg of N‐ NO 2 ‐ g −1 dry soil or sediment for Degrange et al. , 1997 or Feray and Montuelle, 2002). Furthermore, the observed NO 2 ‐ oxidation rate in our study was constant during the 30 h incubation period, although the level of remaining NO 2 ‐ could reach 1 μg of N‐NO 2 ‐ g −1 dry soil.…”

Diversidade bacteriana em solos da Amazônia: variabilidade dos gêneros associados ao processo de nitrificação

“…Diversos estudos abordaram o metabolismo, meio de sobrevivência e crescimento dos oxidadores de nitrito (NOB) em ambientes submetidos à presença de substâncias poluidoras (FÉRAY;MONTUELLE, 2002;FÉRAY;MONTUELLE, 2003;LÓPES-FIUZA et al, 2002), porém poucos examinaram populações naturais de Nitrobacter no solo. Embora a conversão biológica de nitrito em nitrato seja um processo bem conhecido, estudos de populações de Nitrobacter ficam prejudicados pelos métodos inadequados de detecção e contagem.…”