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Water Research Jun 2024The development of continuous flow reactors (CFRs) employing aerobic granular sludge (AGS) for the retrofit of existing wastewater treatment plants (WWTPs) using a...
The development of continuous flow reactors (CFRs) employing aerobic granular sludge (AGS) for the retrofit of existing wastewater treatment plants (WWTPs) using a continuous-flow activated sludge (CFAS) system has garnered increasing interest. This follows the worldwide adoption of AGS technology in sequencing batch reactors (SBRs). The better settleability of AGS compared to AS allows for process intensification of existing wastewater treatment plants without the difficult conversion of often relatively shallow CFRs to deeper AGS-SBRs. To retrofit existing CFAS systems with AGS, achieving both increased hydraulic capacity and enhanced biological nutrient removal necessitates the formation of granular sludge based on the same selective pressures applied in AGS-SBRs. Previous efforts have focussed mainly on the selective wasting of flocculent sludge and retaining granular sludge to drive aerobic granulation. In this study a pilot-scale CFR was developed to best mimic the implementation of the granulation mechanisms of full-scale AGS-SBRs. The pilot-scale reactor was fed with pre-settled municipal wastewater. We established metrics to assess the degree to which the proposed mechanisms were implemented in the pilot-scale CFR and compared them to data from full-scale AGS-SBRs, specifically with respect to the anaerobic distribution of granule forming substrates (GFS). The selective pressures for granular sludge formation were implemented through inclusion of anaerobic upflow selectors with a water depth of 2.5 meters, which yielded a sludge with properties similar to AGS from full-scale SBRs. In comparison to the CFAS system at Harnaschpolder WWTP treating the same pre-settled wastewater, a more than twofold increase in volumetric removal capacity for both phosphorus and nitrogen was achieved. The use of a completely mixed anaerobic selector, as opposed to an anaerobic upflow selector, caused a shift in EBPR activity from the largest towards the smallest size class, while nitrification was majorly unaffected. Anaerobic selective feeding via bottom-feeding is, therefore, favorable for the long-term stability of AGS, especially for less acidified wastewater. The research underlines the potential of AGS for enhancing the hydraulic and biological treatment capacity of existing CFAS systems.
Topics: Sewage; Bioreactors; Anaerobiosis; Aerobiosis; Waste Disposal, Fluid; Wastewater; Pilot Projects
PubMed: 38701553
DOI: 10.1016/j.watres.2024.121531 -
PloS One 2024Bacteria are exposed to reactive oxygen and nitrogen species that provoke oxidative and nitrosative stress which can lead to macromolecule damage. Coping with stress...
Bacteria are exposed to reactive oxygen and nitrogen species that provoke oxidative and nitrosative stress which can lead to macromolecule damage. Coping with stress conditions involves the adjustment of cellular responses, which helps to address metabolic challenges. In this study, we performed a global transcriptomic analysis of the response of Pseudomonas extremaustralis to nitrosative stress, induced by S-nitrosoglutathione (GSNO), a nitric oxide donor, under microaerobic conditions. The analysis revealed the upregulation of genes associated with inositol catabolism; a compound widely distributed in nature whose metabolism in bacteria has aroused interest. The RNAseq data also showed heightened expression of genes involved in essential cellular processes like transcription, translation, amino acid transport and biosynthesis, as well as in stress resistance including iron-dependent superoxide dismutase, alkyl hydroperoxide reductase, thioredoxin, and glutathione S-transferase in response to GSNO. Furthermore, GSNO exposure differentially affected the expression of genes encoding nitrosylation target proteins, encompassing metalloproteins and proteins with free cysteine and /or tyrosine residues. Notably, genes associated with iron metabolism, such as pyoverdine synthesis and iron transporter genes, showed activation in the presence of GSNO, likely as response to enhanced protein turnover. Physiological assays demonstrated that P. extremaustralis can utilize inositol proficiently under both aerobic and microaerobic conditions, achieving growth comparable to glucose-supplemented cultures. Moreover, supplementing the culture medium with inositol enhances the stress tolerance of P. extremaustralis against combined oxidative-nitrosative stress. Concordant with the heightened expression of pyoverdine genes under nitrosative stress, elevated pyoverdine production was observed when myo-inositol was added to the culture medium. These findings highlight the influence of nitrosative stress on proteins susceptible to nitrosylation and iron metabolism. Furthermore, the activation of myo-inositol catabolism emerges as a protective mechanism against nitrosative stress, shedding light on this pathway in bacterial systems, and holding significance in the adaptation to unfavorable conditions.
Topics: Inositol; Pseudomonas; Nitrosative Stress; Gene Expression Regulation, Bacterial; S-Nitrosoglutathione; Aerobiosis; Bacterial Proteins; Gene Expression Profiling; Oxidative Stress
PubMed: 38696454
DOI: 10.1371/journal.pone.0301252 -
Water Research Jun 2024Phage emit communication signals that inform their lytic and lysogenic life cycles. However, little is known regarding the abundance and diversity of the genes...
Phage emit communication signals that inform their lytic and lysogenic life cycles. However, little is known regarding the abundance and diversity of the genes associated with phage communication systems in wastewater treatment microbial communities. This study focused on phage communities within two distinct biochemical wastewater environments, specifically aerobic membrane bioreactors (AeMBRs) and anaerobic membrane bioreactors (AnMBRs) exposed to varying antibiotic concentrations. Metagenomic data from the bench-scale systems were analyzed to explore phage phylogeny, life cycles, and genetic capacity for antimicrobial resistance and quorum sensing. Two dominant phage families, Schitoviridae and Peduoviridae, exhibited redox-dependent dynamics. Schitoviridae prevailed in anaerobic conditions, while Peduoviridae dominated in aerobic conditions. Notably, the abundance of lytic and lysogenic proteins varied across conditions, suggesting the coexistence of both life cycles. Furthermore, the presence of antibiotic resistance genes (ARGs) within viral contigs highlighted the potential for phage to transfer ARGs in AeMBRs. Finally, quorum sensing genes in the virome of AeMBRs indicated possible molecular signaling between phage and bacteria. Overall, this study provides insights into the dynamics of viral communities across varied redox conditions in MBRs. These findings shed light on phage life cycles, and auxiliary genetic capacity such as antibiotic resistance and bacterial quorum sensing within wastewater treatment microbial communities.
Topics: Bioreactors; Bacteriophages; Anaerobiosis; Phylogeny; Quorum Sensing; Drug Resistance, Microbial; Wastewater; Aerobiosis
PubMed: 38677036
DOI: 10.1016/j.watres.2024.121620 -
The Science of the Total Environment Jun 2024Drained peatlands in temperate climates are under threat from climate change and human activities. The resulting decomposition of organic matter plays a major role in...
Drained peatlands in temperate climates are under threat from climate change and human activities. The resulting decomposition of organic matter plays a major role in regulating the associated land subsidence rates, yet the determinants of aerobic and anaerobic peat decomposition rates are not fully understood. In this study, we sought to gain insight into the drivers of decomposition rates in botanically diverse peatlands (sedge, reed, wood, and moss dominant) under oxic and anoxic conditions. Peat samples were collected from the anoxic zone and incubated for 24 h (short) and 15 weeks (long) under either oxic or anoxic conditions. CO emissions, hydrolytic and oxidative exoenzyme potential activities, phenolic compound concentrations, and several edaphic factors were measured at the end of each incubation period. We found that 15 weeks of oxygen exposure of anoxic peat samples accelerated the average CO emissions by 3.9-fold. Reed and sedge peat respired more than wood and moss peat under anoxic conditions. Interestingly, CO emissions from anoxic peat layers under permanently anoxic conditions were substantial and given the thickness of peat deposits in the field, such activities may play an important role in long-term land subsidence rates and total CO emissions from drained peatlands. The results from the long-term incubations showed that decomposition rates appear to be also controlled by factors other than oxygen intrusion such as substrate availability. In summary, the botanical composition of the peat matrix, incubation conditions and time of incubation are all important factors that need to be considered when predicting peat decomposition and subsequent land subsidence rates.
Topics: Soil; Anaerobiosis; Wetlands; Aerobiosis; Environmental Monitoring; Climate Change; Carbon Dioxide
PubMed: 38670365
DOI: 10.1016/j.scitotenv.2024.172639 -
Applied Microbiology and Biotechnology Apr 2024Poly-hydroxybutyrate (PHB) is an environmentally friendly alternative for conventional fossil fuel-based plastics that is produced by various microorganisms. Large-scale...
Poly-hydroxybutyrate (PHB) is an environmentally friendly alternative for conventional fossil fuel-based plastics that is produced by various microorganisms. Large-scale PHB production is challenging due to the comparatively higher biomanufacturing costs. A PHB overproducer is the haloalkaliphilic bacterium Halomonas campaniensis, which has low nutritional requirements and can grow in cultures with high salt concentrations, rendering it resistant to contamination. Despite its virtues, the metabolic capabilities of H. campaniensis as well as the limitations hindering higher PHB production remain poorly studied. To address this limitation, we present HaloGEM, the first high-quality genome-scale metabolic network reconstruction, which encompasses 888 genes, 1528 reactions (1257 gene-associated), and 1274 metabolites. HaloGEM not only displays excellent agreement with previous growth data and experiments from this study, but it also revealed nitrogen as a limiting nutrient when growing aerobically under high salt concentrations using glucose as carbon source. Among different nitrogen source mixtures for optimal growth, HaloGEM predicted glutamate and arginine as a promising mixture producing increases of 54.2% and 153.4% in the biomass yield and PHB titer, respectively. Furthermore, the model was used to predict genetic interventions for increasing PHB yield, which were consistent with the rationale of previously reported strategies. Overall, the presented reconstruction advances our understanding of the metabolic capabilities of H. campaniensis for rationally engineering this next-generation industrial biotechnology platform. KEY POINTS: A comprehensive genome-scale metabolic reconstruction of H. campaniensis was developed. Experiments and simulations predict N limitation in minimal media under aerobiosis. In silico media design increased experimental biomass yield and PHB titer.
Topics: Halomonas; Nitrogen; Hydroxybutyrates; Polyesters; Metabolic Networks and Pathways; Biomass; Glucose; Polyhydroxybutyrates
PubMed: 38662130
DOI: 10.1007/s00253-024-13111-8 -
Nature Communications Apr 2024Paddy fields are hotspots of microbial denitrification, which is typically linked to the oxidation of electron donors such as methane (CH) under anoxic and hypoxic...
Paddy fields are hotspots of microbial denitrification, which is typically linked to the oxidation of electron donors such as methane (CH) under anoxic and hypoxic conditions. While several anaerobic methanotrophs can facilitate denitrification intracellularly, whether and how aerobic CH oxidation couples with denitrification in hypoxic paddy fields remains virtually unknown. Here we combine a ~3300 km field study across main rice-producing areas of China and CH-DNA-stable isotope probing (SIP) experiments to investigate the role of soil aerobic CH oxidation in supporting denitrification. Our results reveal positive relationships between CH oxidation and denitrification activities and genes across various climatic regions. Microcosm experiments confirm that CH and methanotroph addition promote gene expression involved in denitrification and increase nitrous oxide emissions. Moreover, CH-DNA-SIP analyses identify over 70 phylotypes harboring genes associated with denitrification and assimilating C, which are mostly belonged to Rubrivivax, Magnetospirillum, and Bradyrhizobium. Combined analyses of C-metagenome-assembled genomes and C-metabolomics highlight the importance of intermediates such as acetate, propionate and lactate, released during aerobic CH oxidation, for the coupling of CH oxidation with denitrification. Our work identifies key microbial taxa and pathways driving coupled aerobic CH oxidation and denitrification, with important implications for nitrogen management and greenhouse gas regulation in agroecosystems.
Topics: Methane; Oryza; Denitrification; Soil Microbiology; Oxidation-Reduction; China; Soil; Aerobiosis; Bacteria; Nitrous Oxide; Phylogeny; Carbon Isotopes; Metagenome
PubMed: 38658559
DOI: 10.1038/s41467-024-47827-y -
Poultry Science Jun 2024The formation of Campylobacter jeuni biofilms on processing surfaces is a significant concern in poultry processing, contributing to food safety risks. This study...
The formation of Campylobacter jeuni biofilms on processing surfaces is a significant concern in poultry processing, contributing to food safety risks. This study focused on assessing the biofilm forming capabilities of 12 field isolates of C. jejuni of different aerotolerance categories on stainless steel surfaces, a prevalent material in poultry processing environments. Working cultures of each isolate were prepared to approximately 6 log CFU/mL and incubated on stainless steel coupons under microaerobic or aerobic conditions at room temperature or 42°C for 72 h. Biofilm attached cells were enumerated using direct plating and biofilm density was measured using a crystal violet assay by measuring the optical density (OD) a. Data analysis was conducted using the PROC GLIMMIX procedure in SAS 9.4 with a significance level of 0.05. The study revealed a notable interaction between aerotolerance categories and temperature (P < 0.039) impacting the number of biofilms attached C. jejuni cells on stainless steel coupons. All isolates had significantly higher counts when incubated at 42°C compared to room temperature, regardless of oxygen level (P < 0.001). Furthermore, stronger biofilm density was observed at 42°C compared to room temperature, regardless of oxygen level. These findings underscore the influence of temperature on the biofilm forming ability of C. jejuni. The ability of these field isolates to form biofilms under various environmental conditions suggests a heightened potential for surface colonization and increased infection risk in poultry processing facilities.
Topics: Biofilms; Campylobacter jejuni; Stainless Steel; Temperature; Aerobiosis; Animals; Food Microbiology
PubMed: 38652947
DOI: 10.1016/j.psj.2024.103753 -
PeerJ 2024The appropriate sample handling for human fecal microbiota studies is essential to prevent changes in bacterial composition and quantities that could lead to...
BACKGROUND
The appropriate sample handling for human fecal microbiota studies is essential to prevent changes in bacterial composition and quantities that could lead to misinterpretation of the data.
METHODS
This study firstly identified the potential effect of aerobic and anaerobic fecal sample collection and transport materials on microbiota and quantitative microbiota in healthy and fat-metabolic disorder Thai adults aged 23-43 years. We employed metagenomics followed by 16S rRNA gene sequencing and 16S rRNA gene qPCR, to analyze taxonomic composition, alpha diversity, beta diversity, bacterial quantification, Pearson's correlation with clinical factors for fat-metabolic disorder, and the microbial community and species potential metabolic functions.
RESULTS
Our study successfully obtained microbiota results in percent and quantitative compositions. Each sample exhibited quality sequences with a >99% Good's coverage index, and a relatively plateau rarefaction curve. Alpha diversity indices showed no statistical difference in percent and quantitative microbiota OTU richness and evenness, between aerobic and anaerobic sample transport materials. Obligate and facultative anaerobic species were analyzed and no statistical difference was observed. Supportively, the beta diversity analysis by non-metric multidimensional scale (NMDS) constructed using various beta diversity coefficients showed resembling microbiota community structures between aerobic and anaerobic sample transport groups ( = 0.86). On the other hand, the beta diversity could distinguish microbiota community structures between healthy and fat-metabolic disorder groups ( = 0.02), along with Pearson's correlated clinical parameters (., age, liver stiffness, GGT, BMI, and TC), the significantly associated bacterial species and their microbial metabolic functions. For example, genera such as and in healthy human gut provide functions in metabolisms of cofactors and vitamins, biosynthesis of secondary metabolites against gut pathogens, energy metabolisms, digestive system, and carbohydrate metabolism. These microbial functional characteristics were also predicted as healthy individual biomarkers by LEfSe scores. In conclusion, this study demonstrated that aerobic sample collection and transport (<48 h) did not statistically affect the microbiota and quantitative microbiota analyses in alpha and beta diversity measurements. The study also showed that the short-term aerobic sample collection and transport still allowed fecal microbiota differentiation between healthy and fat-metabolic disorder subjects, similar to anaerobic sample collection and transport. The core microbiota were analyzed, and the findings were consistent. Moreover, the microbiota-related metabolic potentials and bacterial species biomarkers in healthy and fat-metabolic disorder were suggested with statistical bioinformatics (., ).
Topics: Humans; Adult; Gastrointestinal Microbiome; Feces; Thailand; Male; RNA, Ribosomal, 16S; Female; Young Adult; Specimen Handling; Anaerobiosis; Aerobiosis; Metagenomics; Southeast Asian People
PubMed: 38650647
DOI: 10.7717/peerj.17270 -
Brazilian Oral Research 2024This study aimed to identify and characterize the antimicrobial susceptibility profile of bacteria found in primary endodontic infections in the teeth of patients...
This study aimed to identify and characterize the antimicrobial susceptibility profile of bacteria found in primary endodontic infections in the teeth of patients treated at the Dental Clinic of the University of Ribeirão Preto, São Paulo, Brazil. From September to December 2019, samples were obtained from 21 patients with primary endodontic infections. The collections were carried out in triplicate using paper cones placed close to the total length of the root canal. Bacterial isolation was performed in Brain Heart Infusion agar, Blood agar, and other selective culture media cultured at 37°C for up to 48 h under aerobiosis and microaerophilic conditions. The bacterial species were identified using the Vitek 2 automated system. The disk diffusion method on agar Müeller-Hinton was used to assess antimicrobial susceptibility with the recommended antimicrobials for each identified bacterial species. A total of 49 antibiotics were evaluated. Fifteen of the 21 samples collected showed bacterial growth, and 17 bacterial isolates were found. There were 10 different bacterial species identified: Enterococcus faecalis (four isolates), Streptococcus mitis/oralis (three isolates), Streptococcus anginosus (three isolates) being the most common, followed by Staphylococcus epidermidis, Enterococcus faecium, Streptococcus constellatus, Streptococcus alactolyticus, Enterobacter cloacae, Klebsiella variicola, and Providencia rettgeri (one isolate of each species). The analysis demonstrated significant susceptibility to most of the tested antibiotics. However, some Enterococcus isolates resisted the antibiotic's erythromycin, ciprofloxacin, and tetracycline. A Staphylococcus epidermidis isolate was characterized as multidrug-resistant. Five Streptococcus isolates were non-susceptible to all antibiotics tested.
Topics: Humans; Agar; Microbial Sensitivity Tests; Brazil; Anti-Bacterial Agents; Enterococcus faecium; Culture Media; Anti-Infective Agents
PubMed: 38597544
DOI: 10.1590/1807-3107bor-2024.vol38.0024 -
The Science of the Total Environment May 2024In situ aerobic cometabolism of groundwater contaminants has been demonstrated to be a valuable bioremediation technology to treat many legacy and emerging contaminants... (Review)
Review
In situ aerobic cometabolism of groundwater contaminants has been demonstrated to be a valuable bioremediation technology to treat many legacy and emerging contaminants in dilute plumes. Several well-designed and documented field studies have shown that this technology can concurrently treat multiple contaminants and reach very low cleanup goals. Fundamentally different from metabolism-based biodegradation of contaminants, microorganisms that cometabolically degrade contaminants do not obtain sufficient carbon and energy from the degradation process to support their growth and require an exogenous growth supporting primary substrate. Successful applications of aerobic cometabolic treatment therefore require special considerations beyond conventional in situ bioremediation, such as competitive inhibition between growth-supporting primary substrate(s) and contaminant non-growth substrates, toxic effects resulting from contaminant degradation, and differences in microbial population dynamics exhibited by biostimulated indigenous consortia versus bioaugmentation cultures. This article first provides a general review of microbiological factors that are likely to affect the rate of aerobic cometabolic biodegradation. We subsequently review fourteen well documented field-scale aerobic cometabolic bioremediation studies and summarize the underlying microbiological factors that may affect the performance observed in these field studies. The combination of microbiological and engineering principles gained from field testing leads to insights and recommendations on planning, design, and operation of an in situ aerobic cometabolic treatment system. With a vision of more aerobic cometabolic treatments being considered to tackle large, dilute plumes, we present several novel topics and future research directions that can potentially enhance technology development and foster success in implementing this technology for environmental restoration.
Topics: Biodegradation, Environmental; Aerobiosis; Groundwater; Water Pollutants, Chemical
PubMed: 38485017
DOI: 10.1016/j.scitotenv.2024.171667