Effects of various COD/NO ratios on NOx removal performance and microbial communities in a BTF-ABR integrated system.

In this study, we investigated the removal performance of NOx and stability of the biotrickling filter-anaerobic baffled reactor (BTF-ABR) integrated system at various chemical oxygen demand (COD)/NO ratios (12.18, 6.71, and 4.63 in stages 1, 2, and 3, respectively) under 3.5% O2 and 50 ± 0.5 °C conditions for the first time. The results showed that the maximum elimination capacity of NOx was 4.46, 8.16, and 11.58 g/(m3·h) in stages 1, 2, and 3, respectively. The minimum operating cost in terms of glucose was 4.79 g of glucose/g of NO. However, a COD/NO ratio of 12.18 resulted in a wastage of carbon sources, while a COD/NO ratio of 4.63 led to about 20 mg/m3 N2O emission at the end of the study. Highly bacteria diversity and positive co-occurrence networks at the COD/NO ratio of 6.71 were the main reasons for no intermediate accumulation or N2O emission. Analysis of real-time polymerase chain reaction (PCR) indicated that nirS and norB were more sensitive to the changes in the COD/NO ratios than other denitrifying genes, and the denitrifiers with nirS filled more ecological niches as the NOx increased. Furthermore, although the decrease in COD/NO ratio significantly impacted the microbial community structure, the NOx RE was stabilized at over 90% because the micro-aerobic environment produced by ABR combined highly diverse microbes and functions in BTF, as well as the coordinated expression of denitrifying genes. Achieving efficient, stable, and low-cost denitrification is feasible in this BTF-ABR integrated system.

Cable bacteria accelerate the anaerobic removal of pyrene in black odorous river sediments.

Cable bacteria play an essential role in biogeochemical processes in sediments by long-distance electron transport (LDET). A potential relationship has been found between cable bacteria and organic contaminant removal; however, the mechanisms remain unclear. In this study, the response of cable bacteria to pyrene was investigated in sediments with and without pyrene, and the effect of cable bacteria on pyrene removal was explored by connecting and blocking the paths of cable bacteria to the suboxic zones. The results showed that pyrene significantly influenced the microbial community structure and the composition of cable bacteria. The pyrene removal efficiencies significantly increased with the enrichment of cable bacteria, while sulfur-reducing microorganisms and aromatic compound degraders were also significantly enriched and correlated with cable bacteria abundance. Metagenomic analysis showed that cable bacteria have a potential LDET-bound acetate/formate respiratory pathway to gain energy. The presence of pyrene probably selects and enriches cable bacteria with a high tolerance to organic contaminants and changes the related functional microbial community, leading to the acceleration of pyrene removal. This study provides new insights into the interaction mechanisms between contaminants and cable bacteria, shedding light on the applications of cable bacteria in the bioremediation of contaminants in sediments.

Water quality drives the distribution of freshwater cable bacteria.

Cable bacteria are a group of recently found filamentous sulfide-oxidizing Desulfobulbaceae that significantly impact biogeochemical cycling. However, the limited understanding of cable bacteria distribution patterns and the driving force hindered our abilities to evaluate and maximize their contribution to environmental health. We evaluated cable bacteria assemblages from ten river sediments in the Pearl River Delta, China. The results revealed a clear biogeographic distribution pattern of cable bacteria, and their communities were deterministically assembled through water quality-driven selection. Cable bacteria are diverse in the river sediments with a few generalists and many specialists, and the water quality IV and V environments are the "hot spot." We then provided evidence on their morphology, function, and genome to demonstrate how water quality might shape the cable bacteria assemblages. Reduced cell width, inhibited function, and water quality-related adaptive genomic traits were detected in sulfide-limited water quality III and contaminant-stressed water quality VI environments. Specifically, those genomic traits were contributed to carbon and sulfur metabolism in the water quality III environment and stress resistance in the water quality VI environment. Overall, these findings provided a helpful baseline in evaluating the contribution of cable bacteria in the freshwater ecosystem and suggested that their high diversity and flexibility in phylogeny, morphology, and genome allowed them to adapt and contribute to various environmental conditions.

Novosphingobium percolationis sp. nov. and Novosphingobium huizhouense sp. nov., isolated from landfill leachate of a domestic waste treatment plant.

Two strains designated as c1T and c7T, were isolated from the landfill leachate of a domestic waste treatment plant in Huizhou City, Guangdong Province, PR China. The cells of both strains were aerobic, rod-shaped, non-motile and formed yellow colonies on Reasoner's 2A agar plates. Strain c1T grew at 10-42 °C (optimum, 30 °C), pH 4.5-10.5 (optimum, pH 7.0) and 0-2.0 % (w/v) NaCl (optimum, 0-0.5 %). Strain c7T grew at 10-42 °C (optimum, 30 °C), pH 4.5-10.5 (optimum, pH 6.0) and 0-2.0 % (w/v) NaCl (optimum, 0-0.5 %). Phylogenetic analyses revealed that strains c1T and c7T belong to the genus Novosphingobium. The 16S rRNA gene sequence similarities of strains c1T and c7T to the type strains of Novosphingobium species were 94.5-98.2 % and 94.3-99.1 %, respectively. The calculated pairwise average nucleotide identity values among strains c1T, c7T and the reference strains were in the range of 75.2-85.9 % and the calculated pairwise average amino acid identity values among strains c1T, c7T and reference strains were in the range of 72.0-88.3 %. Their major respiratory quinone was Q-10, and the major cellular fatty acids were C18 : 1 ω7c, C18 : 0, C16 : 1 ω7c, C16 : 0 and C14 : 0 2OH. The major polar lipids of strains c1T and c7T were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, sphingoglycolipid, unidentified lipids and unidentified phospholipid. Based on phenotypic, chemotaxonomic, phylogenetic and genomic results from this study, strains c1T and c7T should represent two independent novel species of Novosphingobium, for which the names Novosphingobium percolationis sp. nov. (type strain c1T=GDMCC 1.2555T=KCTC 82826T) and Novosphingobium huizhouense sp. nov. (type strain c7T=GDMCC 1.2556T=KCTC 82827T) are proposed. The gene function annotation results of strains c1T and c7T suggest that they could play an important role in the degradation of organic pollutants.

Evaluation of NOx removal from flue gas and Fe(II)EDTA regeneration using a novel BTF-ABR integrated system.

A promising process is under development for the removal of NOx and regeneration of Fe(II)EDTA in a novel biotrickling filter-anaerobic baffled reactor (BTF-ABR) integrated system at 50 ± 0.5 â„ƒ. In this work, we investigated the NOx removal capacity of a BTF under different O2 concentrations (7.0 vol%, 5.25 vol% and 3.5 vol%), and tested the effect of an ABR on NOx removal and regeneration of Fe(II)EDTA. The results showed that the NOx removal capacity was significantly increased with the O2 concentration reduced from 7.0% to 3.5%. The microoxygen environment produced by the BTF-ABR integrated system was more conducive to the removal of NOx and regeneration of Fe(II)EDTA compared with that in the BTF. Real-time polymerase chain reaction (PCR) analysis showed that the coordinated expression of denitrification genes was the major reason for no N2O emission, along with no nitrate and nitrite accumulation. The 16S rRNA gene amplicon sequencing analysis showed that the cooperation of denitrifying bacteria (Klebsiella, Petrimonas, Rhodococcus and Ochrobactium) and iron-reducing bacteria (Klebsiella, Geobacter and Petrimonas) in the system was the key to the stable and efficient removal of NOx and the regeneration of Fe(II)EDTA simultaneously.

Cable bacteria extend the impacts of elevated dissolved oxygen into anoxic sediments.

Profound biogeochemical responses of anoxic sediments to the fluctuation of dissolved oxygen (DO) concentration in overlaying water are often observed, despite oxygen having a limited permeability in sediments. This contradiction is indicative of previously unrecognized mechanism that bridges the oxic and anoxic sediment layers. Using sediments from an urban river suffering from long-term polycyclic aromatic hydrocarbons (PAHs) contamination, we analyzed the physicochemical and microbial responses to artificially elevated DO (eDO) in the overlying water over 9 weeks of incubation. Significant changes in key environmental parameters and microbial diversity were detected over the 0-6 cm sediment depth, along with accelerated degradation of PAHs, despite that eDO only increased the porewater DO in the millimeter subfacial layer. The dynamics of physicochemical and microbial properties coincided well with significantly increased presence of centimeter-long sulfide-oxidizing cable bacteria filaments under eDO, and were predominantly driven by cable bacteria metabolic activities. Phylogenetic ecological network analyses further revealed that eDO reinforced cable bacteria associated interspecific interactions with functional microorganisms such as sulfate reducers, PAHs degraders, and electroactive microbes, suggesting enhanced microbial syntrophy taking advantage of cable bacteria metabolism for the regeneration of SO42- and long-distance electron transfer. Together, our results suggest cable bacteria may mediate the impacts of eDO in anaerobic sediments by altering sediment physiochemical properties and by reinforcing community interactions. Our findings highlight the ecological importance of cable bacteria in sediments.

Metagenomic insights into the metabolism and evolution of a new Thermoplasmata order (Candidatus Gimiplasmatales).

Thermoplasmata is a widely distributed and ecologically important archaeal class in the phylum Euryarchaeota. Because few cultures and genomes are available, uncharacterized Thermoplasmata metabolisms remain unexplored. In this study, we obtained four medium- to high-quality archaeal metagenome-assembled genomes (MAGs) from the filamentous fragments of black-odorous aquatic sediments (Foshan, Guangdong, China). Based on their 16S rRNA gene and ribosomal protein phylogenies, the four MAGs belong to the previously unnamed Thermoplasmata UBA10834 clade. We propose that this clade (five reference genomes from the Genome Taxonomy Database (GTDB) and four MAGs from this study) be considered a new order, Candidatus Gimiplasmatales. Metabolic pathway reconstructions indicated that the Ca. Gimiplasmatales MAGs can biosynthesize isoprenoids and nucleotides de novo. Additionally, some taxa have genes for formaldehyde and acetate assimilation, and the Wood-Ljungdahl CO2 -fixation pathway, indicating a mixotrophic lifestyle. Sulfur reduction, hydrogen metabolism, and arsenic detoxification pathways were predicted, indicating sulfur-, hydrogen-, and arsenic-transformation potentials. Comparative genomics indicated that the H4 F Wood-Ljungdahl pathway of both Ca. Gimiplasmatales and Methanomassiliicoccales was likely obtained by the interdomain lateral gene transfer from the Firmicutes. Collectively, this study elucidates the taxonomic and potential metabolic diversity of the new order Ca. Gimiplasmatales and the evolution of this subgroup and its sister lineage Methanomassiliicoccales.

Synergistic interactions of Desulfovibrio and Petrimonas for sulfate-reduction coupling polycyclic aromatic hydrocarbon degradation.

Microbial sulfate-reduction coupling polycyclic aromatic hydrocarbon (PAH) degradation is an important process for the remediation of contaminated sediments. However, little is known about core players and their mechanisms in this process due to the complexity of PAH degradation and the large number of microorganisms involved. Here we analyzed potential core players in a black-odorous sediment using gradient-dilution culturing, isolation and genomic/metagenomic approaches. Along the dilution gradient, microbial PAH degradation and sulfate consumption were not decreased, and even a significant (p = 0.003) increase was observed in the degradation of phenanthrene although the microbial diversity declined. Two species, affiliated with Desulfovibrio and Petrimonas, were commonly present in all of the gradients as keystone taxa and showed as the dominant microorganisms in the single colony (SB8) isolated from the highest dilution culture with 93.49% and 4.73% of the microbial community, respectively. Desulfovibrio sp. SB8 and Petrimonas sp. SB8 could serve together as core players for sulfate-reduction coupling PAH degradation, in which Desulfovibrio sp. SB8 could degrade PAHs to hexahydro-2-naphthoyl through the carboxylation pathway while Petrimonas sp. SB8 might degrade intermediate metabolites of PAHs. This study provides new insights into the microbial sulfate-reduction coupling PAH degradation in black-odorous sediments.