The mechanisms of in vivo commensal control of Clostridioides difficile virulence

We define multiple mechanisms by which commensals protect against or worsen Clostridioides difficile infection. Using a systems-level approach we show how two species of Clostridia with distinct metabolic capabilities modulate the pathogen’s virulence to impact host survival. Gnotobiotic mice colonized with the amino acid fermenter Clostridium bifermentans survived infection, while colonization with the butyrate-producer, Clostridium sardiniense, more rapidly succumbed. Systematic in vivo analyses revealed how each commensal altered the pathogen’s carbon source metabolism, cellular machinery, stress responses, and toxin production. Protective effects were replicated in infected conventional mice receiving C. bifermentans as an oral bacteriotherapeutic that prevented lethal infection. Leveraging a systematic and organism-level approach to host-commensal-pathogen interactions in vivo, we lay the groundwork for mechanistically-informed therapies to treat and prevent this disease.

Municipal sludge management and disposal in South Korea: Status and a new sustainable approach

Based on figures from 2002, 5,216 ton/d of the municipal sludge is produced from 184 large municipal wastewater treatment plants in 111 cities with total treatment capacity of 19,229,745 m3/d. Even though the large amount of sludge disposal has depended greatly on ocean disposal and landfills until recently, the fraction of sludge reuse has gradually increased from 2.7% to 7%, since 1991. Due to a need of resources recovery from the sludge, high cost requirement of incineration and legislative regulation, recent new research is mainly focused on resources recovery and its reuse from the municipal sludge, such as high performance acid fermenter with pathogen reduction, crystallization (struvite and hydroxyapatite) using waste lime, cofermentation of municipal sludge with food waste, aerobic composting with P crystallization, vermistabilization, lime treatment, etc. Current research and practical activities with some efforts for the new technical development as well as environmental law and regulation are reviewed.

Use of a new anaerobic-aerobic sequencing batch reactor system to enhance biological phosphorus removal

A two-stage anaerobic-aerobic sequencing batch reactor (SBR) system (PAF-SBR) was developed to enhance biological phosphorus removal in the sequencing batch reactors. The system performance was evaluated against a conventional SBR system in parallel lab-scale reactors at room temperature, using the degritted raw wastewater as the feed. The SRT for the anaerobic SBR which is named PAF (Primary Acid Fermenter) was 12 days, and for both the BNR reactors was 10 days. All reactors were run at 3 cycles per day. A significant difference (P=0.01) was observed between the performances of the two systems. The Ortho-P concentration in the effluent from the PAF-SBR was mostly below 0.5 mg/L while in the conventional SBR was generally above 1.5 mg/L. Lack of availability of carbon (mean VFA/PSol.=1.1) and long anoxic/anaerobic period were the major causes of inefficient removal of phosphorus in the conventional SBR system. The use of anaerobic stage however increased the mean VFA/PSol. to 11.3 which enhanced Bio-P removal in the PAF-SBR system. Prefermentation also improved the sludge consistency and settleability in the following SBR unit. The results indicated that by using the perfermentation step, the anoxic/anaerobic period in the BNR-SBR could be controlled and reduced to less than 50 minutes, which would reduce the total cycle time from 8 hr to 6 hr.

Comparison of glycolysis and glutaminolysis in Onchocerca volvulus and Brugia pahangi by 13C nuclear magnetic resonance spectroscopy

SummaryComparison of glycolysis in Brugia pahangi and Onchocerca volvulus by C nuclear magnetic resonance (NMR) spectroscopy showed that the former organism is predominantly a lactate fermenter and the latter resembles more closely the metabolism of a mixed acid fermenter producing lactate, succinate, acetate, ethanol, formate and carbon dioxide. Both organisms synthesize glycogen as a storage carbohydrate. Glutaminolysis in both organisms proceeds by the δ-aminobutyrate shunt to produce succinate which is then further metabolized to acetate and carbon dioxide as end-products.