Influence of biofilm thickness on the removal of thirteen different organic micropollutants via a Membrane Aerated Biofilm Reactor (MABR).

The presence of organic micropollutants (OMPs) in natural water bodies has become an emerging concern due to their fast dissemination into natural water sources, high persistence, ubiquitous nature, and detrimental impact on the environment and human health. This study evaluated the Membrane Aerated Biofilm Reactor (MABR) efficiency in the removal of 13 OMPs commonly reported in water. Results demonstrated that OMPs removal is dependent on biofilm thickness and bacterial cell density, microbial community composition and physicochemical properties of OMPs. Effective removals of ammonium and organic carbon (COD, >50%), acetaminophen (70%) and triclosan (99%) were obtained even at early stages of biofilm development (thickness < 0.33 mm, 2.9 ×105 cell mL-1). An increase in biofilm thickness and cell density (1.02 mm, 2.2 ×106 cell mL-1) enhanced the system performance. MABR achieved over 90% removal of nonpolar, hydrophobic and hydrophilic OMPs and 22-69% removal of negatively charged and acidic OMPs. Relative abundances of Zoogloea, Aquabacterium, Leucobacter, Runella, and Paludilbaculum bacteria correlated with the removal of certain OMPs. In addition, MABR achieved up to 96% nitrification and 80% overall COD removal by the end of the experiment. The findings from this study demonstrated MABRs to be a feasible option to treat municipal wastewater polluted by OMPs.

Transition from unclassified Ktedonobacterales to Actinobacteria during amorphous silica precipitation in a quartzite cave environment.

The orthoquartzite Imawarì Yeuta cave hosts exceptional silica speleothems and represents a unique model system to study the geomicrobiology associated to silica amorphization processes under aphotic and stable physical-chemical conditions. In this study, three consecutive evolution steps in the formation of a peculiar blackish coralloid silica speleothem were studied using a combination of morphological, mineralogical/elemental and microbiological analyses. Microbial communities were characterized using Illumina sequencing of 16S rRNA gene and clone library analysis of carbon monoxide dehydrogenase (coxL) and hydrogenase (hypD) genes involved in atmospheric trace gases utilization. The first stage of the silica amorphization process was dominated by members of a still undescribed microbial lineage belonging to the Ktedonobacterales order, probably involved in the pioneering colonization of quartzitic environments. Actinobacteria of the Pseudonocardiaceae and Acidothermaceae families dominated the intermediate amorphous silica speleothem and the final coralloid silica speleothem, respectively. The atmospheric trace gases oxidizers mostly corresponded to the main bacterial taxa present in each speleothem stage. These results provide novel understanding of the microbial community structure accompanying amorphization processes and of coxL and hypD gene expression possibly driving atmospheric trace gases metabolism in dark oligotrophic caves.

Evaluation of two autoinducer-2 quantification methods for application in marine environments.

AIM: This study evaluated two methods, namely high performance liquid chromatography with fluorescence detection (HPLC-FLD) and Vibrio harveyi BB170 bioassay, for autoinducer-2 (AI-2) quantification in marine samples. Using both methods, the study also investigated the stability of AI-2 in varying pH, temperature and media, as well as quantified the amount of AI-2 signals in marine samples. METHODS AND RESULTS: HPLC-FLD method showed a higher level of reproducibility and precision compared to V. harveyi BB170 bioassay. Alkaline pH (>8) and high temperature (>37°C) increased the instability of AI-2. The AI-2 concentrations in seawater were low, c. 3·2-27·6 pmol l-1 , whereas 8-week-old marine biofilm grew on an 18·8 cm2 substratum accumulated c. 0·207 nmol of AI-2. CONCLUSION: Both methods have pros and cons for AI-2 quantification in marine samples. Regardless, both methods reported a ubiquitous presence of AI-2 in both planktonic and biomass fractions of seawater, as well as in marine biofilm. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, AI-2 signals were for the first time enumerated in marine samples to reveal the ubiquitous presence of AI-2 in this environment. The findings suggest a possible role of AI-2 in biofilm formation in marine environment, and the contribution of AI-2 in biofilm-associated problems such as biofouling and biocorrosion.

[Incidence of venous air embolism in parturients during cesarean section with regional anesthesia].

The purpose of the study is to probe the situation of venous air embolism (VAE) and the accompanying complications occurring in Chinese parturients in Taiwan during Cesarean section. Sixty ASA physical status class I-II parturients who were subjected to cesarean section under regional anesthesia were evaluated. The sensor of the Doppler device was placed on the anterior chest to detect the rumbles of air when it came to pass, and simultaneously the signs and symptoms following VAE were observed. Our results demonstrated that the usual or normal Doppler heart sound changed in 38 parturients out of 60 (63.3%), and the alteration occurred very often when the uterus was being incised (81.6%), or sutured (97.4%), and concurred strong correlation with such signs and symptoms such as chest tightness or precordial pain (78.9%), shortness of breath (60.5%), and change of heart rate or blood pressure (86.8%). The method of anesthesia (spinal or epidural block) did not have effect on the occurrence of VAE, but different surgical approaches and different positions in which the patients were posed during operation did apparently bring about VAE of variable degree. Besides, supplying of oxygen could mitigate the symptoms produced by VAE. Consequently, the application of Doppler monitor during Cesarean section can detect VAE earlier and more efficiently and thus provides information timely treatment.

Comparison of lower concentrations of lidocaine to suppress bucking before extubation during recovery of general anesthesia.

Thirty females, aged 25-50 years old, scheduled for abdominal total hysterectomy were randomly divided to two groups. For patients in group I, 2 mL 1% lidocaine solution was injected through the catheter on the tube to desensitize the trachea while surgeon started to close the peritoneum. In group II, 2 mL 2% lidocaine was used. The peak cuff pressures generated in the awakening group I patients were 49.0 +/- 2.5 cmH2 O (mean +/- SD) which shows greater than that in group II (27.9 +/- 7.2 cmH2 O), p less than 0.01. Bucking before awakening was also evaluated clinically. One hundred % (15/15) in group I patients bucked compared with 13.3% (2/15) in group II patients (p less than 0.01). Gag reflex was preserved in all patients and none suffered from aspiration postoperatively. Intratracheal administration of two mL 2% lidocaine through the catheter of modified endotracheal tube showed significant effect for suppressing bucking during recovery of general anesthesia.