Seeking key microorganisms for enhancing methane production in anaerobic digestion of waste sewage sludge

Efficient approaches for the utilization of waste sewage sludge have been widely studied. One of them is to use it for the bioenergy production, specifically methane gas which is well-known to be driven by complex bacterial interactions during the anaerobic digestion process. Therefore, it is important to understand not only microorganisms for producing methane but also those for controlling or regulating the process. In this study, azithromycin analogs belonging to macrolide, ketolide, and lincosamide groups were applied to investigate the mechanisms and dynamics of bacterial community in waste sewage sludge for methane production. The stages of anaerobic digestion process were evaluated by measuring the production of intermediate substrates, such as protease activity, organic acids, the quantification of bacteria and archaea, and its community dynamics. All azithromycin analogs used in this study achieved a high methane production compared to the control sample without any antibiotic due to the efficient hydrolysis process and the presence of important fermentative bacteria and archaea responsible in the methanogenesis stage. The key microorganisms contributing to the methane production may be Clostridia, Cladilinea, Planctomycetes, and Alphaproteobacteria as an accelerator whereas Nitrosomonadaceae and Nitrospiraceae may be suppressors for methane production. In conclusion, the utilization of antibiotic analogs of macrolide, ketolide, and lincosamide groups has a promising ability in finding the essential microorganisms and improving the methane production using waste sewage sludge

Tunable hysteresis effect for perovskite solar cells

Perovskite solar cells (PSCs) usually suffer from a hysteresis effect in current–voltage measurements, which leads to an inaccurate estimation of the device e fficiency. Although ion migration, charge trapping/ detrapping, and accumulation have been proposed as a b asis for the hysteresis, the origin of the hysteresis has not been apparently unraveled. Herein we reporte d a tunable hysteresis effect based uniquely on open- circuit voltage variations in printable mesos copic PSCs with a simplified triple-layer TiO 2 /ZrO 2 /carbon architecture. The electrons are collected by the compact TiO 2 /mesoporous TiO 2 (c-TiO 2 /mp-TiO 2 )bilayer, and the holes are collected by the carbon layer. By adj usting the spray deposition cycles for the c-TiO 2 layer andUV-ozonetreatment,weachievedhysteresis-norm al, hysteresis-free, and hysteresis-inverted PSCs. Such unique trends of tunable hysteresis are anal yzed by considering the polarization of the TiO 2 /perovskite interface, which can accumulate positive charges reversibly. Successfully tuning of the hysteresis effect clarifies the critical importance of the c-TiO 2 /perovskite interface in controlling the hysteretic trends observed, providing important insights towards the understanding of this rapidly developing photovoltaic technology

Influence of pretreated activated sludge for electricity generation in microbial fuel cell application.

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

Croceicoccus bisphenolivorans sp. nov., a bisphenol A- degrading bacterium isolated from seawater

A bisphenol A- degrading bacterium, designated as strain H4T, was isolated from surface seawater, which was sampled from the Jiulong River estuary in southeast PR China. Strain H4T is Gram- stain- negative, aerobic, short rod- shaped, lacking bacteriochlorophyll a, motile with multifibrillar stalklike fascicle structures and capable of degrading bisphenol A. Growth of strain H4T was observed at 24?45 ?C (optimum, 32 ?C), at pH 5.5?9 (optimum, pH 7.0) and in 0?7 % NaCl (optimum, 2 %; w/v) . The 16S rRNA gene sequence of strain H4T showed highest similarity to Croceicoccus pelagius Ery9T (98.7 %), Croceicoccus sediminis (98.3 %), Croceicoccus naphthovorans PQ-2T (98.1 %) and Croceicoccus ponticola GM-16T (97.6 %), followed by Croceicoccus marinus E4A9T (96.7 %) and Croceicoccus mobilis Ery22T (96.0 %). Phylogenetic analysis revealed that strain H4T fell within a clade comprising the type strains of Croceicoccus species and formed a phyletic line with them that was distinct from other members of the family Erythrobacteraceae. The sole respiratory quinone was quinone 10 (Q-10). The predominant fatty acids (>5 % of the total fatty acids) of strain H4T were summed feature 8 (C18:1 ?6c and/or C18: 1 ?7c), summed feature 3 (C16:1 ?6c and/or C16: 1 ?7c), C17: 1 ?6c and C14:02- OH. The genomic DNA G+C content was 62.8 mol%. In the polar lipid profile, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, two unidentified phospholipids, two sphingoglycolipids and three unknown lipids were the major compounds. Based on the genotypic and phenotypic data, strain H4T represents a novel species of the genus Croceicoccus, for which the name Croceicoccus bisphenolivorans sp. nov. is proposed. The type strain is H4T (=DSM 102182T=MCCC1 K02301T)

Community Structure and Function of Planktonic Crenarchaeota: Changes with Depth in the South China Sea

MOST [2007CB815900]; NSFC [40632013, 40821063, 91028005]; SOA [200805068]; State Key Laboratory of Marine Environmental Science at Xiamen University [MELRS1026]Marine Crenarchaeota represent a widespread and abundant microbial group in marine ecosystems. Here, we investigated the abundance, diversity, and distribution of planktonic Crenarchaeota in the epi-, meso-, and bathypelagic zones at three stations in the South China Sea (SCS) by analysis of crenarchaeal 16S rRNA gene, ammonia monooxygenase gene amoA involved in ammonia oxidation, and biotin carboxylase gene accA putatively involved in archaeal CO(2) fixation. Quantitative PCR analyses indicated that crenarchaeal amoA and accA gene abundances varied similarly with archaeal and crenarchaeal 16S rRNA gene abundances at all stations, except that crenarchaeal accA genes were almost absent in the epipelagic zone. Ratios of the crenarchaeal amoA gene to 16S rRNA gene abundances decreased similar to 2.6 times from the epi- to bathypelagic zones, whereas the ratios of crenarchaeal accA gene to marine group I crenarchaeal 16S rRNA gene or to crenarchaeal amoA gene abundances increased with depth, suggesting that the metabolism of Crenarchaeota may change from the epi- to meso- or bathypelagic zones. Denaturing gradient gel electrophoresis profiling of the 16S rRNA genes revealed depth partitioning in archaeal community structures. Clone libraries of crenarchaeal amoA and accA genes showed two clusters: the "shallow" cluster was exclusively derived from epipelagic water and the "deep" cluster was from meso- and/or bathypelagic waters, suggesting that niche partitioning may take place between the shallow and deep marine Crenarchaeota. Overall, our results show strong depth partitioning of crenarchaeal populations in the SCS and suggest a shift in their community structure and ecological function with increasing depth

Dynamics of Autotrophic Marine Planktonic Thaumarchaeota in the East China Sea

NSFC [41106096, 41191021]; SOA project [201105021]; Science and Technology Planning Project of Xiamen, China [3502Z20102017]; State Key Laboratory of Marine Environmental Science at Xiamen University [MELRS1026]The ubiquitous and abundant distribution of ammonia-oxidizing Thaumarchaeota in marine environments is now well documented, and their crucial role in the global nitrogen cycle has been highlighted. However, the potential contribution of Thaumarchaeota in the carbon cycle remains poorly understood. Here we present for the first time a seasonal investigation on the shelf region (bathymetry <= 200 m) of the East China Sea (ECS) involving analysis of both thaumarchaeal 16S rRNA and autotrophy-related genes (acetyl-CoA carboxylase gene, accA). Quantitative PCR results clearly showed a higher abundance of thaumarchaeal 16S and accA genes in late-autumn (November) than summer (August), whereas the diversity and community structure of autotrophic Thaumarchaeota showed no statistically significant difference between different seasons as revealed by thaumarchaeal accA gene clone libraries. Phylogenetic analysis indicated that shallow ecotypes dominated the autotrophic Thaumarchaeota in the ECS shelf (86.3% of total sequences), while a novel non-marine thaumarchaeal accA lineage was identified in the Changjiang estuary in summer (when freshwater plumes become larger) but not in autumn, implying that Changjiang freshwater discharge played a certain role in transporting terrestrial microorganisms to the ECS. Multivariate statistical analysis indicated that the biogeography of the autotrophic Thaumarchaeota in the shelf water of the ECS was influenced by complex hydrographic conditions. However, an in silico comparative analysis suggested that the diversity and abundance of the autotrophic Thaumarchaeota might be biased by the 'universal' thaumarchaeal accA gene primers Cren529F/Cren981R since this primer set is likely to miss some members within particular phylogenetic groups. Collectively, this study improved our understanding of the biogeographic patterns of the autotrophic Thaumarchaeota in temperate coastal waters, and suggested that new accA primers with improved coverage and sensitivity across phylogenetic groups are needed to gain a more thorough understanding of the role of the autotrophic Thaumarchaeota in the global carbon cycle

Understanding gaseous nitrogen removal through direct measurement of dissolved N2 and N2O in a subtropical river-reservoir system

Dam construction within a river basin modifies hydrology and affects nitrogen (N) removal during transport to coast. In this study, direct measurements of dissolved N2 and N2O were carried out in a subtropical river reservoir (Xipi) in southeast China to understand the effectiveness of reservoirs in removal of fixed N by N gas fluxes. Results showed that larger excess N2 and N2O emissions were found in the riverine zone where effluents from the upper dam mix with the shallow river. Excess N2, mainly derived from denitrification, occurred in the sediment below deep water, while N2O was largely produced from nitrification in the water column, particularly in dry season. Seasonal variation of excess N2 was associated with temperature and DO level, while N2O production was controlled by DIN concentration. The gaseous N dynamics and distribution in the studied reservoir reflected an interactive effect of hydrology, geomorphology and biogeochemistry. In the reservoir lacustrine zone, gaseous N removal accounted for 85% of total retention and less than 1% of DIN loads. The negligible retention of N by the reservoir highlights the importance of appropriate watershed management practices to reduce N losses from terrestrial systems. ? 2014 Elsevier B.V