Exploration and enrichment of methane-oxidizing bacteria derived from a rice paddy field emitting highly concentrated methane

Metabolic diversity shapes vegetation-enhanced methane oxidation in landfill covers: Multi-omics study of rhizosphere microorganisms

Vegetation root exudates have the ability to shape soil microbial community structures, thereby enhancing CH4 bio-oxidation capacity in landfill cover systems. In this study, the CH4 oxidation capacity of indigenous vegetation rhizosphere microorganisms within operational landfill covers in Chongqing, China, was investigated for the first time, with the objective of identifying suitable plant candidates for CH4 mitigation initiatives within landfill cover systems. Furthermore, a multi-omics methodology was employed to explore microbial community structures and metabolic variances within the rhizospheric environment of diverse vegetation types. The primary aim was to elucidate the fundamental factors contributing to divergent CH4 oxidation capacities observed in rhizosphere soils. The findings demonstrated that herbaceous vegetation predominated in landfill covers. Notably, Rumex acetosa exhibited the highest CH4 oxidation capacity in the rhizosphere soil, approximately 20 times greater than that in non-rhizosphere soil. Root exudates played a crucial role in inducing the colonization of CH4-oxidizing functional microorganisms in the rhizosphere, subsequently prompting the development of specific metabolic pathways. This process, in turn, enhanced the functional activity of the microorganisms while concurrently bolstering their tolerance to microbial pollutants. Consequently, the addition of substances like Limonexic acid strengthened the CH4 bio-oxidation process, thereby underscoring the suitability of Rumex acetosa and similar vegetation species as preferred choices for landfill cover vegetation restoration.

Microaerophilic Activated Sludge System for Ammonia Retention toward 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 and organic carbon removal 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 (<0.2 mg/L) and short solids retention times (SRTs) (<5 days) eliminated nitrifying bacteria. The two parallel MASs were successfully operated for 300 days 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, the quantitative polymerase chain reaction of functional genes, and fluorescence in situ hybridization of β-proteobacteria AOB. The microbial analyses also uncovered that filamentous bacteria were positively correlated with effluent turbidity. Together, controlling DO and SRT achieved organic carbon removal and successful ammonia retention, mainly by suppressing AOM activity. This process represents a new nitrogen management paradigm.

Toward sustainable remediation of oil sands fine Tailings-A review

Significant quantities of tailings are produced during the extraction of bitumen from oil sands. Tailings are stored in tailings ponds for several years before they can be appropriately managed. Current fine tailings management approaches include mechanical and/or chemical amendments of fine tailings (FT) to speed up tailings reclamation. However, complex structures of fine tailings, stringent tailings management regulations, failure in production of trafficable deposits with current FT reclamation technologies and biogenic gas (e.g., CH₄) generations have prompted the re-evaluation of current FT remediation technologies and exploration of alternative biological treatments (e.g., bioaugmentation and biostimulation). Biological treatments have proven to effectively remediate environmental pollutants by creating favourable environments for the desire microorganisms. Thus their effects on FT reclamation have been increasingly investigated in the last two decades. Many of these studies confirmed that biological treatments can improve FT dewatering and densification. However, other studies found that not all biological treatments can effectively suppress CH₄ generations or they may lead to the generation of other biogenic gases (e.g., H₂S, N₂O, NO). Therefore, it is critical to identify potential environmental risks associated with the biological treatments before their full-scale applications. This review revolved around two questions. First, whether bioaugmentation and biostimulation methods can improve FT reclamation. Secondly, what are the potential environmental issues that may arise from the applications of biological treatments. To address these questions, the existing peer-reviewed documents on fine tailings management were carefully reviewed to provide an introduction to the currently practiced FT reclamation technologies. Further discussions on biological treatments and their potentials and limitations were also presented. Finally, the review highlighted the knowledge gap in the area of biological treatments of FT and provided recommendations for future research.

Complete Genome Sequence of Methylosinus sp. Strain C49, a Methane-Oxidizing Bacterium Harboring phaABC Genes for Polyhydroxyalkanoate Synthesis

We report a complete genome sequence of Methylosinus sp. strain C49, a methane-oxidizing bacterium (MOB) in the class Alphaproteobacteria, isolated from MOB-enriched biomass. The genome encodes the functional genes for methane oxidation (pmoA) and polyhydroxyalkanoate (PHA) biosynthesis (phaABC). Deciphering the genome will help research toward PHA production by MOB.