Dataset Information

Physicochemical characterization of Pseudomonas stutzeri UFV5 and analysis of its transcriptome under heterotrophic nitrification/aerobic denitrification pathway induction condition.

ABSTRACT: Biological ammonium removal via heterotrophic nitrification/aerobic denitrification (HN/AD) presents several advantages in relation to conventional removal processes, but little is known about the microorganisms and metabolic pathways involved in this process. In this study, Pseudomonas stutzeri UFV5 was isolated from an activated sludge sample from oil wastewater treatment station and its ammonium removal via HN/AD was investigated by physicochemical and molecular approaches to better understand this process and optimize the biological ammonium removal in wastewater treatment plants. Results showed that P. stutzeri UFV5 removed all the ammonium in 48-72?hours using pyruvate, acetate, citrate or sodium succinate as carbon sources, C/N ratios 6, 8, 10 and 12, 3-6% salinities, pH 7-9 and temperatures of 20-40?°C. Comparative genomics and PCR revealed that genes encoding the enzymes involved in anaerobic denitrification process are present in P. stutzeri genome, but no gene that encodes enzymes involved in autotrophic nitrification was found. Furthermore, transcriptomics showed that none of the known enzymes of autotrophic nitrification and anaerobic denitrification had their expression differentiated and an upregulation of the biosynthesis machinery and protein translation was observed, besides several genes with unknown function, indicating a non-conventional mechanism involved in HN/AD process.

SUBMITTER: Silva LCF

PROVIDER: S-EPMC7010759 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Physicochemical characterization of Pseudomonas stutzeri UFV5 and analysis of its transcriptome under heterotrophic nitrification/aerobic denitrification pathway induction condition.

Silva Lívia Carneiro Fidélis LCF Lima Helena Santiago HS Mendes Tiago Antônio de Oliveira TAO Sartoratto Adilson A Sousa Maira Paula MP de Souza Rodrigo Suhett RS de Paula Sérgio Oliveira SO de Oliveira Valéria Maia VM Silva Cynthia Canedo CC

Scientific reports 20200210 1

Biological ammonium removal via heterotrophic nitrification/aerobic denitrification (HN/AD) presents several advantages in relation to conventional removal processes, but little is known about the microorganisms and metabolic pathways involved in this process. In this study, Pseudomonas stutzeri UFV5 was isolated from an activated sludge sample from oil wastewater treatment station and its ammonium removal via HN/AD was investigated by physicochemical and molecular approaches to better understan ...[more]

PMID: 32042029

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Project description:The expression of denitrification by a facultatively anaerobic bacterium requires as exogenous signals a low oxygen tension concomitant with an N oxide. We have studied the role of nitric oxide (NO), nitrous oxide (N2O), and nitrite as signal molecules for the expression of the denitrification apparatus of Pseudomonas stutzeri. Transcriptional kinetics of structural genes were monitored by Northern blot analysis in a 60-min time frame after cells were exposed to an N oxide signal. To differentiate the inducer role of NO from that of nitrite, mRNA kinetics were monitored under anoxic conditions in a nirF strain, where NO generation from nitrite is prevented because of a defect in heme D(1) biosynthesis. NO-triggered responses were monitored from the nirSTB operon (encoding cytochrome cd(1) nitrite reductase), the norCB operon (encoding NO reductase), nosZ (encoding nitrous oxide reductase), and nosR (encoding a putative regulator). Transcription of nirSTB and norCB was activated by 5 to 50 nM NO, whereas the nosZ promoter required about 250 nM. Nitrite at 5 to 50 nM elicited no response. At a threshold concentration of 650 nM N2O, we observed in the anoxic cell the transient appearance of nosZ and nosR transcripts. Constant levels of transcripts of both genes were observed in an anoxic cell sparged with N2O. NO at 250 nM stimulated in this cell type the expression of nos genes severalfold. The transcription factor DnrD, a member of the FNR-CRP family, was found to be part of the NO-triggered signal transduction pathway. However, overexpression of dnrD in an engineered strain did not result in NirS synthesis, indicating a need for activation of DnrD. NO modified the transcriptional pattern of the dnrD operon by inducing the transcription of dnrN and dnrO, located upstream of dnrD. Insertional mutagenesis of dnrN altered the kinetic response of the nirSTB operon towards nitrite. Our data establish NO and DnrD as key elements in the regulatory network of denitrification in P. stutzeri. The NO response adds to the previously identified nitrate-nitrite response mediated by the NarXL two-component system for the expression of respiratory nitrate reductase encoded by the narGHJI operon.

Project description:Simultaneous nitrification-denitrification (SND) is, in theory, a key advantage of aerobic granular sludge systems over conventional activated sludge systems. But practical experience and literature suggests that SND and thus total nitrogen removal are limited during treatment of municipal wastewater using AGS systems. This study thus aims at quantifying the extent and understanding the mechanisms of SND during treatment of municipal wastewater with aerobic granular sludge (AGS) systems. Experiments (long-term and batch-tests) as well as mathematical modelling were performed. Our experimental results demonstrate that SND is significantly limited during treatment of low-strength municipal wastewater with AGS systems (14-39%), while almost full SND is observed when treating synthetic influent containing only diffusible substrate (90%). Our simulations demonstrate that the main mechanisms behind limited SND are (1) the dynamics of anoxic zone formation inside the granule, (2) the diffusibility and availability of electron-donors in those zones and (3) the aeration mode. The development of anoxic zones is driven by the utilisation of oxygen in the upper layers of the granule leading to transport limitations of oxygen inside the granule; this effect is closely linked to granule size and wastewater composition. Development of anoxic zones during the aerobic phase is limited for small granules at constant aeration at bulk dissolved oxygen (DO) concentration of 2 mgO2 L-1, and anoxic zones only develop during a brief period of the aerated phase for large granules. Modelling results further indicate that a large fraction of electron-donors are actually utilised in aerobic rather than anoxic redox zones - in the bulk or at the granule surface. Thus, full SND cannot be achieved with AGS treating low strength municipal wastewater if a constant DO is maintained during the aeration phase. Optimised aeration strategies are therefore required. 2-step and alternating aeration are tested successfully using mathematical modelling and increase TN removal to 40-79%, without compromising nitrification, and by shifting electron-donor utilisation towards anoxic redox conditions.

Dataset Information

Physicochemical characterization of Pseudomonas stutzeri UFV5 and analysis of its transcriptome under heterotrophic nitrification/aerobic denitrification pathway induction condition.

Publications

Physicochemical characterization of Pseudomonas stutzeri UFV5 and analysis of its transcriptome under heterotrophic nitrification/aerobic denitrification pathway induction condition.

Similar Datasets

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