Biology subjects

Terada, A.

Publications and source records attributed to Terada, A..

3 recordsLinked to original sources

bioRxiv2024

Meta-omic insights into active bacteria mediating N2O mitigation and dissimilatory nitrate reduction to ammonium in an ammonia recovery bioreactor

Shifting from ammonia removal to recovery is the current strategy in wastewater treatment management. We recently developed a microaerophilic activated sludge (MAS) system for retaining ammonia while removing organic carbon with minimal N2O emissions. A comprehensive understanding of nitrogen metabolisms in the MAS system is essential to optimize system performance. Here, we employed metagenomics and metatranscriptomics analyses to characterize the microbial community structure and activity during the transition from a microaerophilic to an aerobic condition. A hybrid approach of high-quality Illumina short reads and Nanopore long reads recovered medium-to high-quality 98 non-redundant metagenome-assembled genomes (MAGs) from the MAS communities. The suppressed bacterial ammonia monooxygenase (amoA) expression was upregulated after shifting from a microaerophilic to an aerobic condition. The 73 MAGs (>74% of the total) from 11 bacterial phyla harbored genes encoding proteins involved in nitrate respiration; 39 MAGs ([~]53%) carried N2O reductase (nosZ) genes with the predominance of clade II nosZ (31 MAGs), and 24 MAGs ([~]33%) possessed nitrite reductase (ammonia forming) genes (nrfA). Clade II nosZ and nrfA genes exhibited the highest and second-highest expressions among nitrogen metabolism genes, indicating robust N2O consumption and ammonification. Non-denitrifying clade II nosZ bacteria, Cloacibacterium spp., in the most abundant and active phylum Bacteroioda, were likely major N2O sinks. Elevated dissolved oxygen (DO) concentration inhibited clade II nosZ expression but not nrfA expression, potentially switching phenotypes from N2O reduction to ammonification. Collectively, the multi-omics analysis illuminated vital bacteria responsible for N2O reduction and ammonification in microaerophilic and aerobic conditions, facilitating high-performance ammonia recovery.

ecology↗

bioRxiv2023

Potential survival strategies of novel comammox and nitrite-oxidizing Nitrospira present in a reactor treating high-ammonia brackish landfill leachate

Nitrification is mediated by numerous different microorganisms, but knowledge of their ecophysiologies is insufficient. Leachate in the late stages of landfill operation provides a brackish environment with a high ammonia concentration, and methanol is added as an electron donor for denitrification. Such a unique environment may contain novel nitrifiers. Here, we present metagenomic analysis of the microbiome from a closed landfill leachate treatment facility to investigate the identity and functions of nitrifiers. Using a genome-centric approach with metagenomic analysis, we retrieved draft genomes for a novel complete ammonia-oxidizing (comammox) bacterium Nitrospira LAS72; and canonical Nitrospira LAS18, clustered within a novel sub-lineage VII of Nitrospira; Candidatus Nitrosocosmicus LAS21 and Nitrosarchaeum LAS73, belonging to the ammonia-oxidizing archaea (AOA). This is the first evidence of comammox Nitrospira in a high-ammonia-containing brackish environment. Canonical ammonia-oxidizing bacteria were not detected. Given the brackish environment and supplementation of methanol used in the facility, we also investigated the methanol metabolism of these nitrifiers and their potential to produce compatible solutes as osmoprotectants. Uniquely among Nitrospira, comammox Nitrospira LAS72 possesses genes associated with formaldehyde reductase and glycine betaine biosynthesis. Thus, Nitrospira LAS72 may proliferate because of the availability of formaldehyde upstream of carbon metabolism and adapt to fluctuating osmotic pressure by producing a variety of compatible solutes. The discovery of this novel comammox Nitrospira, and canonical Nitrospira forming a new sub-lineage VII in an ammonia-concentrated brackish environment broadens our knowledge of the diversity and functions of nitrifying microorganisms.

microbiology↗

bioRxiv2022

Microaerophilic activated sludge system for ammonia recovery from high-strength nitrogenous wastewater: Performance and microbial communities

A transition to ammonia recovery from wastewater has started; however, a technology for sustainable nitrogen retention in the form of ammonia is still in development. This study validated a microaerophilic activated sludge (MAS) system to efficiently retain ammonia from high-strength nitrogenous wastewater. The MAS is based on conventional activated sludge (CAS) with aerobic and settling compartments. Low dissolved oxygen (DO) concentrations (<0.1 mg/L) and short solid retention times (SRTs) (<5 d) eliminated nitrifying bacteria. The two parallel MASs were successfully operated for 300 d and had ammonia retention of 101.7 {+/-} 24.9% and organic carbon removal of 85.5 {+/-} 8.9%. The MASs mitigated N2O emissions with an emission factor of <0.23%, much lower than the default value of CAS (1.6%). A short-term step-change test demonstrated that N2O indicated the initiation of nitrification and the completion of denitrification in the MAS. The parallel MASs had comparable microbial diversity, promoting organic carbon oxidation while inhibiting ammonia-oxidizing microorganisms (AOMs), as revealed by 16S rRNA gene amplicon sequencing, qPCR of functional genes, and fluorescent in situ hybridization of {beta}-Proteobacteria AOB. The microbial analyses also uncovered that filamentous bacteria were positively correlated with effluent turbidity. Together, controlling DO and SRT achieved successful ammonia retention, mainly by suppressing AOM activity. This process represents a new nitrogen management paradigm. SynopsisMoving from nitrogen removal to nitrogen recovery is critical for establishing a sustainable society. We provided proof-of-the-concept for a novel ammonia retention technology by retrofitting an activated sludge system.

microbiology↗