Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs

ABSTRACT Ammonia availability due to chloramination can promote the growth of nitrifying organisms, which can deplete chloramine residuals and result in operational problems for drinking water utilities. In this study, we used a metagenomic approach to determine the identity and functional potential...

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Autores principales:	Sarah C. Potgieter, Zihan Dai, Stephanus N. Venter, Makhosazana Sigudu, Ameet J. Pinto
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	chloramination drinking water systems metagenomics nitrification nitrogen metabolism Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/abf510dfa10046bcbef8e0a9007c857e
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spelling	oai:doaj.org-article:abf510dfa10046bcbef8e0a9007c857e2021-11-15T15:29:17ZMicrobial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs10.1128/mSphere.00274-202379-5042https://doaj.org/article/abf510dfa10046bcbef8e0a9007c857e2020-04-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00274-20https://doaj.org/toc/2379-5042ABSTRACT Ammonia availability due to chloramination can promote the growth of nitrifying organisms, which can deplete chloramine residuals and result in operational problems for drinking water utilities. In this study, we used a metagenomic approach to determine the identity and functional potential of microorganisms involved in nitrogen biotransformation within chloraminated drinking water reservoirs. Spatial changes in the nitrogen species included an increase in nitrate concentrations accompanied by a decrease in ammonium concentrations with increasing distance from the site of chloramination. This nitrifying activity was likely driven by canonical ammonia-oxidizing bacteria (i.e., Nitrosomonas) and nitrite-oxidizing bacteria (i.e., Nitrospira) as well as by complete-ammonia-oxidizing (i.e., comammox) Nitrospira-like bacteria. Functional annotation was used to evaluate genes associated with nitrogen metabolism, and the community gene catalogue contained mostly genes involved in nitrification, nitrate and nitrite reduction, and nitric oxide reduction. Furthermore, we assembled 47 high-quality metagenome-assembled genomes (MAGs) representing a highly diverse assemblage of bacteria. Of these, five MAGs showed high coverage across all samples, which included two Nitrosomonas, Nitrospira, Sphingomonas, and Rhizobiales-like MAGs. Systematic genome-level analyses of these MAGs in relation to nitrogen metabolism suggest that under ammonia-limited conditions, nitrate may be also reduced back to ammonia for assimilation. Alternatively, nitrate may be reduced to nitric oxide and may potentially play a role in regulating biofilm formation. Overall, this study provides insight into the microbial communities and their nitrogen metabolism and, together with the water chemistry data, improves our understanding of nitrogen biotransformation in chloraminated drinking water distribution systems. IMPORTANCE Chloramines are often used as a secondary disinfectant when free chlorine residuals are difficult to maintain. However, chloramination is often associated with the undesirable effect of nitrification, which results in operational problems for many drinking water utilities. The introduction of ammonia during chloramination provides a potential source of nitrogen either through the addition of excess ammonia or through chloramine decay. This promotes the growth of nitrifying microorganisms and provides a nitrogen source (i.e., nitrate) for the growth for other organisms. While the roles of canonical ammonia-oxidizing and nitrite-oxidizing bacteria in chloraminated drinking water systems have been extensively investigated, those studies have largely adopted a targeted gene-centered approach. Further, little is known about the potential long-term cooccurrence of complete-ammonia-oxidizing (i.e., comammox) bacteria and the potential metabolic synergies of nitrifying organisms with their heterotrophic counterparts that are capable of denitrification and nitrogen assimilation. This study leveraged data obtained for genome-resolved metagenomics over a time series to show that while nitrifying bacteria are dominant and likely to play a major role in nitrification, their cooccurrence with heterotrophic organisms suggests that nitric oxide production and nitrate reduction to ammonia may also occur in chloraminated drinking water systems.Sarah C. PotgieterZihan DaiStephanus N. VenterMakhosazana SiguduAmeet J. PintoAmerican Society for Microbiologyarticlechloraminationdrinking water systemsmetagenomicsnitrificationnitrogen metabolismMicrobiologyQR1-502ENmSphere, Vol 5, Iss 2 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	chloramination drinking water systems metagenomics nitrification nitrogen metabolism Microbiology QR1-502
spellingShingle	chloramination drinking water systems metagenomics nitrification nitrogen metabolism Microbiology QR1-502 Sarah C. Potgieter Zihan Dai Stephanus N. Venter Makhosazana Sigudu Ameet J. Pinto Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
description	ABSTRACT Ammonia availability due to chloramination can promote the growth of nitrifying organisms, which can deplete chloramine residuals and result in operational problems for drinking water utilities. In this study, we used a metagenomic approach to determine the identity and functional potential of microorganisms involved in nitrogen biotransformation within chloraminated drinking water reservoirs. Spatial changes in the nitrogen species included an increase in nitrate concentrations accompanied by a decrease in ammonium concentrations with increasing distance from the site of chloramination. This nitrifying activity was likely driven by canonical ammonia-oxidizing bacteria (i.e., Nitrosomonas) and nitrite-oxidizing bacteria (i.e., Nitrospira) as well as by complete-ammonia-oxidizing (i.e., comammox) Nitrospira-like bacteria. Functional annotation was used to evaluate genes associated with nitrogen metabolism, and the community gene catalogue contained mostly genes involved in nitrification, nitrate and nitrite reduction, and nitric oxide reduction. Furthermore, we assembled 47 high-quality metagenome-assembled genomes (MAGs) representing a highly diverse assemblage of bacteria. Of these, five MAGs showed high coverage across all samples, which included two Nitrosomonas, Nitrospira, Sphingomonas, and Rhizobiales-like MAGs. Systematic genome-level analyses of these MAGs in relation to nitrogen metabolism suggest that under ammonia-limited conditions, nitrate may be also reduced back to ammonia for assimilation. Alternatively, nitrate may be reduced to nitric oxide and may potentially play a role in regulating biofilm formation. Overall, this study provides insight into the microbial communities and their nitrogen metabolism and, together with the water chemistry data, improves our understanding of nitrogen biotransformation in chloraminated drinking water distribution systems. IMPORTANCE Chloramines are often used as a secondary disinfectant when free chlorine residuals are difficult to maintain. However, chloramination is often associated with the undesirable effect of nitrification, which results in operational problems for many drinking water utilities. The introduction of ammonia during chloramination provides a potential source of nitrogen either through the addition of excess ammonia or through chloramine decay. This promotes the growth of nitrifying microorganisms and provides a nitrogen source (i.e., nitrate) for the growth for other organisms. While the roles of canonical ammonia-oxidizing and nitrite-oxidizing bacteria in chloraminated drinking water systems have been extensively investigated, those studies have largely adopted a targeted gene-centered approach. Further, little is known about the potential long-term cooccurrence of complete-ammonia-oxidizing (i.e., comammox) bacteria and the potential metabolic synergies of nitrifying organisms with their heterotrophic counterparts that are capable of denitrification and nitrogen assimilation. This study leveraged data obtained for genome-resolved metagenomics over a time series to show that while nitrifying bacteria are dominant and likely to play a major role in nitrification, their cooccurrence with heterotrophic organisms suggests that nitric oxide production and nitrate reduction to ammonia may also occur in chloraminated drinking water systems.
format	article
author	Sarah C. Potgieter Zihan Dai Stephanus N. Venter Makhosazana Sigudu Ameet J. Pinto
author_facet	Sarah C. Potgieter Zihan Dai Stephanus N. Venter Makhosazana Sigudu Ameet J. Pinto
author_sort	Sarah C. Potgieter
title	Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
title_short	Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
title_full	Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
title_fullStr	Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
title_full_unstemmed	Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs
title_sort	microbial nitrogen metabolism in chloraminated drinking water reservoirs
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/abf510dfa10046bcbef8e0a9007c857e
work_keys_str_mv	AT sarahcpotgieter microbialnitrogenmetabolisminchloraminateddrinkingwaterreservoirs AT zihandai microbialnitrogenmetabolisminchloraminateddrinkingwaterreservoirs AT stephanusnventer microbialnitrogenmetabolisminchloraminateddrinkingwaterreservoirs AT makhosazanasigudu microbialnitrogenmetabolisminchloraminateddrinkingwaterreservoirs AT ameetjpinto microbialnitrogenmetabolisminchloraminateddrinkingwaterreservoirs
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Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs

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