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      Growth of Nitrosococcus-Related Ammonia Oxidizing Bacteria Coincides with Extremely Low pH Values in Wastewater with High Ammonia Content

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          Abstract

          Ammonia oxidation decreases the pH in wastewaters where alkalinity is limited relative to total ammonia. The activity of ammonia oxidizing bacteria (AOB), however, typically decreases with pH and often ceases completely in slightly acidic wastewaters. Nevertheless, nitrification at low pH has been reported in reactors treating human urine, but it has been unclear which organisms are involved. In this study, we followed the population dynamics of ammonia oxidizing organisms and reactor performance in synthetic fully hydrolyzed urine as the pH decreased over time in response to a decrease in the loading rate. Populations of the β-proteobacterial Nitrosomonas europaea lineage were abundant at the initial pH close to 6, but the growth of a possibly novel Nitrosococcus-related AOB genus decreased the pH to the new level of 2.2, challenging the perception that nitrification is inhibited entirely at low pH values, or governed exclusively by β-proteobacterial AOB or archaea. With the pH shift, nitrite oxidizing bacteria were not further detected, but nitrous acid (HNO 2) was still removed through chemical decomposition to nitric oxide (NO) and nitrate. The growth of acid-tolerant γ-proteobacterial AOB should be prevented, by keeping the pH above 5.4, which is a typical pH limit for the N. europaea lineage. Otherwise, the microbial community responsible for high-rate nitrification can be lost, and strong emissions of hazardous volatile nitrogen compounds such as NO are likely.

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          Most cited references47

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          The diversity and biogeography of soil bacterial communities.

          For centuries, biologists have studied patterns of plant and animal diversity at continental scales. Until recently, similar studies were impossible for microorganisms, arguably the most diverse and abundant group of organisms on Earth. Here, we present a continental-scale description of soil bacterial communities and the environmental factors influencing their biodiversity. We collected 98 soil samples from across North and South America and used a ribosomal DNA-fingerprinting method to compare bacterial community composition and diversity quantitatively across sites. Bacterial diversity was unrelated to site temperature, latitude, and other variables that typically predict plant and animal diversity, and community composition was largely independent of geographic distance. The diversity and richness of soil bacterial communities differed by ecosystem type, and these differences could largely be explained by soil pH (r(2) = 0.70 and r(2) = 0.58, respectively; P < 0.0001 in both cases). Bacterial diversity was highest in neutral soils and lower in acidic soils, with soils from the Peruvian Amazon the most acidic and least diverse in our study. Our results suggest that microbial biogeography is controlled primarily by edaphic variables and differs fundamentally from the biogeography of "macro" organisms.
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            Ubiquity and diversity of ammonia-oxidizing archaea in water columns and sediments of the ocean.

            Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, occurs in a wide variety of environments and plays a central role in the global nitrogen cycle. Catalyzed by the enzyme ammonia monooxygenase, the ability to oxidize ammonia was previously thought to be restricted to a few groups within the beta- and gamma-Proteobacteria. However, recent metagenomic studies have revealed the existence of unique ammonia monooxygenase alpha-subunit (amoA) genes derived from uncultivated, nonextremophilic Crenarchaeota. Here, we report molecular evidence for the widespread presence of ammonia-oxidizing archaea (AOA) in marine water columns and sediments. Using PCR primers designed to specifically target archaeal amoA, we find AOA to be pervasive in areas of the ocean that are critical for the global nitrogen cycle, including the base of the euphotic zone, suboxic water columns, and estuarine and coastal sediments. Diverse and distinct AOA communities are associated with each of these habitats, with little overlap between water columns and sediments. Within marine sediments, most AOA sequences are unique to individual sampling locations, whereas a small number of sequences are evidently cosmopolitan in distribution. Considering the abundance of nonextremophilic archaea in the ocean, our results suggest that AOA may play a significant, but previously unrecognized, role in the global nitrogen cycle.
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              The influence of soil pH on the diversity, abundance and transcriptional activity of ammonia oxidizing archaea and bacteria.

              Autotrophic ammonia oxidation occurs in acid soils, even though laboratory cultures of isolated ammonia oxidizing bacteria fail to grow below neutral pH. To investigate whether archaea possessing ammonia monooxygenase genes were responsible for autotrophic nitrification in acid soils, the community structure and phylogeny of ammonia oxidizing bacteria and archaea were determined across a soil pH gradient (4.9-7.5) by amplifying 16S rRNA and amoA genes followed by denaturing gradient gel electrophoresis (DGGE) and sequence analysis. The structure of both communities changed with soil pH, with distinct populations in acid and neutral soils. Phylogenetic reconstructions of crenarchaeal 16S rRNA and amoA genes confirmed selection of distinct lineages within the pH gradient and high similarity in phylogenies indicated a high level of congruence between 16S rRNA and amoA genes. The abundance of archaeal and bacterial amoA gene copies and mRNA transcripts contrasted across the pH gradient. Archaeal amoA gene and transcript abundance decreased with increasing soil pH, while bacterial amoA gene abundance was generally lower and transcripts increased with increasing pH. Short-term activity was investigated by DGGE analysis of gene transcripts in microcosms containing acidic or neutral soil or mixed soil with pH readjusted to that of native soils. Although mixed soil microcosms contained identical archaeal ammonia oxidizer communities, those adapted to acidic or neutral pH ranges showed greater relative activity at their native soil pH. Findings indicate that different bacterial and archaeal ammonia oxidizer phylotypes are selected in soils of different pH and that these differences in community structure and abundances are reflected in different contributions to ammonia oxidizer activity. They also suggest that both groups of ammonia oxidizers have distinct physiological characteristics and ecological niches, with consequences for nitrification in acid soils.
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                Author and article information

                Journal
                Environ Sci Technol
                Environ. Sci. Technol
                es
                esthag
                Environmental Science & Technology
                American Chemical Society
                0013-936X
                1520-5851
                16 May 2017
                20 June 2017
                : 51
                : 12
                : 6857-6866
                Affiliations
                []Eawag, Swiss Federal Institute of Aquatic Science and Technology , 8600 Dübendorf, Switzerland
                []Eawag, Swiss Federal Institute of Aquatic Science and Technology , 6047 Kastanienbaum, Switzerland
                [§ ]Institute of Environmental Engineering, ETH Zürich , 8093 Zürich, Switzerland
                []Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University , 9100 Aalborg, Denmark
                []Department of Biotechnology, Delft University of Technology , Delft, 2629 HZ, The Netherlands
                []Department of Civil and Environmental Engineering, Northwestern University , Evanston, Illinois 60208, United States
                [# ]Laboratory for Air Pollution/Environmental Technology, Empa, Swiss Federal Laboratories for Materials Science and Technology , 8600 Dübendorf, Switzerland
                Author notes
                [* ]Phone: +41 58 765 5360; fax: +41 58 765 5808; e-mail: kai.udert@ 123456eawag.ch ; address: Process Engineering, Überlandstrasse 133, 8600 Dübendorf, Switzerland.
                Article
                10.1021/acs.est.7b00392
                5538757
                28509546
                007023eb-eedd-4a17-a31c-8be0e3d1dad1
                Copyright © 2017 American Chemical Society

                This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.

                History
                : 20 January 2017
                : 16 May 2017
                : 16 May 2017
                Categories
                Article
                Custom metadata
                es7b00392
                es-2017-00392x

                General environmental science
                General environmental science

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