• Energy Research

A facultative anaerobic bacterium, designated as strain SCS5, was isolated from the anodic biofilm of a mediator-less microbial fuel cell using acetate as the electron donor and α-FeOOH as the electron acceptor. The isolate was Gram-negative, motile, and shaped as short rods (0.9-1.3 μm in length and 0.4-0.5 μm in width). A phylogenetic analysis of the 16S rRNA, gyrB, and rpoD genes suggested that strain SCS5 belonged to the Aeromonas genus in the Aeromonadaceae family and exhibited the highest 16S rRNA gene sequence similarity (99.45%) with Aeromonas jandaei ATCC 49568. However, phenotypic, cellular fatty acid profile, and DNA G+C content analyses revealed that there were some distinctions between strain SCS5 and the type strain A. jandaei ATCC 49568. The optimum growth temperature, pH, and NaCl (%) for strain SCS5 were 35°C, 7.0, and 0.5% respectively. The DNA G+C content of strain SCS5 was 59.18%. The isolate SCS5 was capable of reducing insoluble iron oxide (α-FeOOH) and transferring electrons to extracellular material (the carbon electrode). The electrochemical activity of strain SCS5 was corroborated by cyclic voltammetry and a Raman spectroscopic analysis. The cyclic voltammogram of strain SCS5 revealed two pairs of oxidation-reduction peaks under anaerobic and aerobic conditions. In contrast, no redox pair was observed for A. jandaei ATCC 49568. Thus, isolated strain SCS5 is a novel exoelectrogenic bacterium phylogenetically related to A. jandaei, but shows distinct electrochemical activity from its close relative A. jandaei ATCC 49568.

The response of freshwater bacterial community to anthropogenic disturbance has been well documented, yet the studies of freshwater archaeal community are rare, especially in lotic environments. Here, we investigated planktonic and benthic archaeal communities in a human-perturbed watershed (Jiulong River Watershed, JRW) of southeast China by using Illumina 16S ribosomal RNA gene amplicon sequencing. The results of taxonomic assignments indicated that SAGMGC-1, Methanobacteriaceae, Methanospirillaceae, and Methanoregulaceae were the four most abundant families in surface waters, accounting for 12.65, 23.21, 18.58 and 10.97 % of planktonic communities, whereas Nitrososphaeraceae and Miscellaneous Crenarchaeotic Group occupied more than 49 % of benthic communities. The compositions of archaeal communities and populations in waters and sediments were significantly different from each other. Remarkably, the detection frequencies of families Methanobacteriaceae and Methanospirillaceae, and genera Methanobrevibacter and Methanosphaera in planktonic communities correlated strongly with bacterial fecal indicator, suggesting some parts of methanogenic Archaea may come from fecal contamination. Because soluble reactive phosphorus (SRP) and the ratio of dissolved inorganic nitrogen to SRP instead of nitrogen nutrients showed significant correlation with several planktonic Nitrosopumilus- and Nitrosotalea-like OTUs, Thaumarchaeota may play an unexplored role in biogeochemical cycling of river phosphorus. Multivariate statistical analyses revealed that the variation of α-diversity of planktonic archaeal community was best explained by water temperature, whereas nutrient concentrations and stoichiometry were the significant drivers of β-diversity of planktonic and benthic communities. Taken together, these results demonstrate that the structure of archaeal communities in the JRW is sensitive to anthropogenic disturbances caused by riparian human activities.

Influence of different pretreated sludge for electricity generation in microbial fuel cells (MFCs) was investigated in this study. Pre-treatment has shown significant improvement in MFC electricity productivity especially from microwave treated sludge. Higher COD reduction in the MFC has been revealed from microwave treated sludge with 55% for total and 85% for soluble COD, respectively. Nonetheless, longer ozonation treatment did not give additional advantage compared to the raw sludge. On the other hand, samples from anodes were analyzed using the 16S rRNA gene-based pyrosequencing technique for microbial community analysis. There was substantial difference in community compositions among MFCs fed with different pretreated sludge. Bacteroidetes was the abundant bacterial phylum dominated in anodes of higher productivity MFCs. These results demonstrate that using waste sludge as the substrate in MFCs could achieve both sludge reduction and electricity generation, and proper pre-treatment of sludge could improve the overall process performance.

Bench-scale decentralized wastewater treatment systems using microbial fuel cell (MFC) techniques were constructed for simultaneous removal of carbonaceous and nitrogenous pollutants and electricity production from wastewater. The MFC was operated in continuous mode and immobilized Paracoccus pantotrophus cells were added in the cathodic compartment to achieve simultaneous nitrification-denitrification. After 150-day operation, the MFC system could effectively remove >96% COD and 100% ammonium, with 60-80% total nitrogen removal and around 0.2V voltage production. The results of copper (Cu) shock load showed that although 125 mg L(-1) Cu (II) would deteriorate the effluent quality and completely inhibit the electricity production, the microbial populations restored their ability to treat wastewater and produce electricity after a period around 30 days. Community analysis by the 454 pyrosequencing technique showed that the microbial compositions were significantly different and decreased in diversity after the Cu shock load.

Abstract Bacteria communities, as key drivers of energy flow and nutrient recycling in rivers, usually consist of a few abundant taxa and many rare taxa. During the last decades, rivers on the Tibetan Plateau have experienced dramatic land surface changes under climate change and anthropogenic disturbances. However, the responses of abundant and rare taxa to such changes and disturbances still remains unclear. In this study, we explored the biogeography and drivers of the abundant and rare bacteria in Yarlung Tsangpo River sediments on the Tibetan Plateau. Our study demonstrated that changes in surrounding land-use patterns, especially in forest land, bare land and cropland, had profound influences on the distribution of the abundant and rare sediment bacteria in the Yarlung Tsangpo River. Although both communities exhibited significant distance-decay patterns, dispersal limitation was the dominant process in the abundant community, while the rare community was mainly driven by heterogeneous selection. Our results also revealed that the abundant bacteria exhibited stronger adaptation across environmental gradients than the rare bacteria. The similar biogeographic patterns but contrasting assembly processes in abundant and rare communities may result from the differences in their environmental adaptation processes. This work provides valuable insights into the importance of land surface changes in influencing the biogeographic patterns of bacteria in fluvial sediments, which helps to predict their activities and patterns in Tibetan rivers under future global climate change and anthropogenic disturbances.

This study evaluates the efficiency of a sustainable technology represented in an integrated pilot-scale system, which includes a facultative pond (FP), a high-rate algal pond (HRAP), and a rock filter (RF) for wastewater treatment to produce water that complies with the Egyptian standards for treated wastewater reuse. Still, limited data are available on pathogen removal through HRAP systems. Thus, in this study, the performance of the integrated system was investigated for the removal of Escherichia coli (E. coli), coliform bacteria, eukaryotic pathogens (Cryptosporidium spp., Giardia intestinalis, and helminth ova), somatic coliphages (SOMCPH), and human adenovirus (HAdV). Furthermore, physicochemical parameters were determined in order to evaluate the performance of the integrated system. The principal component analysis and non-metric multidimensional scaling analysis showed a strong significant effect of the integrated system on changing the physicochemical and microbial parameters from inlet to outlet. The mean log10 removal values for total coliform, fecal coliform, and E. coli were 5.67, 5.62, and 5.69, respectively, while 0.88 log10 and 1.65 log10 reductions were observed for HAdV and SOMCPH, respectively. The mean removal of Cryptosporidium spp. and Giardia intestinalis was 0.52 and 2.42 log10, respectively. The integrated system achieved 100% removal of helminth ova. The results demonstrated that the system was able to improve the chemical and microbial characteristics of the outlet to acceptable levels for non-food crops irrigation. Such findings together with low operation and construction costs of HRAPs should facilitate wider implementation of these nature-based systems in remote and rural communities. Overall, this study provides a novel insight into the performance of such systems to eliminate multiple microbial pathogens from wastewater.

Carbon dioxide (CO2) is the main greenhouse gas; hence, processes are needed to remove it from the environment. Here, CO2 was used as the substrate to generate methane (CH4) by using enriched methanogens after anaerobic enrichment of waste activated sludge (WAS); therefore, we demonstrate that methanogens from WAS have significant potential for converting the greenhouse gas CO2 into the fuel methane. Methane production was found to increase 70 fold by active methanogens in the enriched methanogens culture after 3 days in the presence of H2 and CO2. Throughout the process, CO2 was completely consumed after 4 days of incubation in the vials after sparging with a mixture of H2 and CO2, resulting in significant biological CO2 sequestration by methanogens. Using a mixture of H2 and 13 CO2, we also demonstrated that the methane produced is due to the utilization of CO2. Microbial community studies via by quantitative real time PCR (qRT-PCR) indicate the dominance of archaea in the enriched methanogens culture of WAS. Archaeal community studies of the enriched methanogens via highthroughput 16S rRNA sequencing also showed that the archaea consist mainly of hydrogenotrophic and aceticlastic methanogens such as Methanobacteriaceae, Methanospirillaceae and Methanosarcinaceae spp. which are actively grown in H2 and CO2. We envision that CO2 gas from power plants can be directed to enriched methanogens of WAS to prevent release of this greenhouse gas while generating a useful biofuel (methane) or other valuable products using this single carbon atom.

Antibiotic resistance genes (ARGs) became an emerging contaminant, and were found to accumulate in natural and man-made environments. A comprehensive understanding of the diversity and abundance of ARGs in pristine environments is critical for defining the baseline levels of environmental ARGs. However, there is limited information available on the ARG profiles of pristine environments, especially for shallow-sea hydrothermal vents ecosystems. Here, we combined 16S rRNA gene full-length amplicon sequencing and high-throughput quantitative PCR (HT-qPCR) to study the bacterial communities, and ARG abundance and diversity in the shallow-sea hydrothermal vent ecosystem of the Kueishantao Islet. The results of the 16S rRNA gene amplicon sequencing showed that several sulfur-cycling related bacterial genera, including Thiomicrorhabdus, Thioreductor, Sulfurovum, Sulfurimonas and Lebetimonas, dominated in the water column of the shallow-sea system. Temperature was the significant factor shaping the bacterial communities. The results of HT-qPCR analysis showed that the Kueishantao shallow-sea system harbored the lowest diversity (average 10 ARG subtypes) and abundance (average 1.0 × 10−3 copy per bacterial cell) of ARGs compared with other pristine (i.e., Tibet lake sediments, marine water and sediments) and anthropogenic-disturbed (i.e., drinking water reservoirs, urban ponds and wastewater treatment plants) environments. Procrustes analysis demonstrated a concordant pattern between the compositions of bacterial communities and ARGs in the shallow-sea system, while variation partition analysis revealed that the shared effects of physicochemical and bacterial communities explained >80% of the variation in the composition of ARGs. These results suggest that the vent bacterial communities and local environmental factors played an important role in shaping the distribution of the ARG profiles. Our study provides the first comprehensive overview of the background level of ARGs in a shallow-sea hydrothermal vent ecosystem.