Aerobic methanotrophic bacteria consume methane as it diffuses away from methanogenic zones of soil and sediment. They act as a biofilter to reduce methane emissions to the atmosphere, and they are therefore targets in strategies to combat global climate change. No cultured methanotroph grows optimally below pH 5, but some environments with active methane cycles are very acidic. Here we describe an extremely acidophilic methanotroph that grows optimally at pH 2.0-2.5. Unlike the known methanotrophs, it does not belong to the phylum Proteobacteria but rather to the Verrucomicrobia, a widespread and diverse bacterial phylum that primarily comprises uncultivated species with unknown genotypes. Analysis of its draft genome detected genes encoding particulate methane monooxygenase that were homologous to genes found in methanotrophic proteobacteria. However, known genetic modules for methanol and formaldehyde oxidation were incomplete or missing, suggesting that the bacterium uses some novel methylotrophic pathways. Phylogenetic analysis of its three pmoA genes (encoding a subunit of particulate methane monooxygenase) placed them into a distinct cluster from proteobacterial homologues. This indicates an ancient divergence of Verrucomicrobia and Proteobacteria methanotrophs rather than a recent horizontal gene transfer of methanotrophic ability. The findings show that methanotrophy in the Bacteria is more taxonomically, ecologically and genetically diverse than previously thought, and that previous studies have failed to assess the full diversity of methanotrophs in acidic environments.

A novel, multi-walled carbon nanotubes (CNT) modified white C3N4 composite (CNT/white C3N4) with enhanced visible-light-response photoactivity was prepared. The white C3N4 and CNT combined together and formed the CNT/white C3N4 composite due to electrostatically-driven self-assembly with the hydrothermal method. The as-prepared white C3N4 and CNT/white C3N4 composite photocatalyst were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-vis absorption spectra, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photoelectrochemical i-t curves were tested using several on-off cycles of light irradiation. The photoactivity of the catalysts was evaluated by degrading methylene blue (MB) dye solution. The results showed that the photoactivity for the degradation of MB solution was in the following order: CNT/white C3N4 composite > C3N4 > the white C3N4. The photoactivity of the CNT/white C3N4 composite was 66.5% and 34.5% higher than that of the white C3N4 sample and that of the C3N4 at 1.5 h, respectively. The degradation rate of the CNT/white C3N4 photocatalyst was almost 8.1 times as high as that of the white C3N4. The results indicated that CNT played an important role, which led to the efficient separation of the photo-generated charge carriers. The reason why the photoactivity of the CNT/white C3N4 was much higher than that of C3N4 and the white C3N4 was discussed. A possible mechanism of CNT on the enhancement of composites' visible light performance was also proposed.

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Several studies have shown that soil microorganisms play a key role in the success of plant invasion. Thus, ecologists have become increasingly interested in understanding the ecological effects of biological invasion on soil microbial communities given continuing increase in the effects of invasive plants on native ecosystems. This paper aims to provide a relatively complete depiction of the characteristics of soil microbial communities under different degrees of plant invasion. Rhizospheric soils of the notorious invasive plant Wedelia trilobata with different degrees of invasion (uninvaded, low-degree, and high-degree using its coverage in the invaded ecosystems) were collected from five discrete areas in Hainan Province, P. R. China. Soil physicochemical properties and community structure of soil microorganisms were assessed. Low degrees of W. trilobata invasion significantly increased soil pH values whereas high degrees of invasion did not significantly affected soil pH values. Moreover, the degree of W. trilobata invasion exerted significant effects on soil Ca concentration but did not significantly change other indices of soil physicochemical properties. Low and high degrees of W. trilobata invasion increased the richness of the soil fungal community but did not pose obvious effects on the soil bacterial community. W. trilobata invasion also exerted obvious effects on the community structure of soil microorganisms that take part in soil nitrogen cycling. These changes in soil physicochemical properties and community structure of soil microbial communities mediated by different degrees of W. trilobata invasion may present significant functions in further facilitating the invasion process.

In enzymatic conversion of biomass, how to degrade cellulose into fermentable glucose in an economic, efficient, and clean way has become an important subject. As for the application of cellulase in cellulose degradation, the process optimization in enzyme engineering is urgently desired. The traditional multistep purification processes lead to rising production costs and reduced activity of cellulase; meanwhile, the difficulty in reusability of cellulase has also become a big baffle in the cost-effective application of cellulase in biomass degradation. In this paper, the biocatalyst Glu-linker-ELP-GB (GLEGB) containing binary tags, elastin-like polypeptide (ELP), and graphene-binding (GB), was constructed to simplify the purification and immobilization of βglucosidase (Glu) from Coptotermes formosanus. A high recovery rate (97.2%) and purification fold (18.7) of GLEGB was obtained by only one round of inverse transition cycling (ITC) with 0.5 M (NH 4 ) 2 SO 4 at 25 °C in a short incubating time of 10 min. The purification performance of the one-round ITC method is superior to the commonly used Ni-NTA resin affinity method. Furthermore, the high loading amounts of GLEGB immobilized on GO (698.2 mg g −1 ) and C 3 N 4 (527.3 mg g −1 ) were achieved by the synergistic effects of ELP and GB tags. The storage stability and thermal stability of GLEGB was significantly enhanced after immobilization. The recombinant GLEGB immobilized on GO, MGO, graphite, C 3 N 4 , C200, and C400 retained 71.4%, 69.5%, 75.1%, 61.2%, 73.5%, and 80.2% of their initial activities respectively after eight cycles. It is worth mentioning that the K m values of GLEGB immobilized on lamellar carbon materials including GO, MGO, and C 3 N 4 are very close to free GLEGB, showing a high affinity of recombinant GLEGB to substrate. To our knowledge, this is the first report on enzyme-linker-ELP-GB system with wide application prospect in the efficient purification and immobilization of enzyme, which can achieve the goal of reducing cost and improving efficiency of biocatalyst in enzymatic conversion of biomass.

How to improve the accessibility of immobilized cellulase to insoluble cellulose and recover immobilized enzyme from remaining insoluble substrate is a challenge to the efficient hydrolysis of cellulose into glucose. The objective of this work is to solve the problems mentioned above by the immobilization of cellulase onto poly(methacrylamide-coacrylic acid) (PMAAc), developing a reversibly soluble− insoluble biocatalyst with upper critical solution temperature (UCST) of 16 °C. The as-prepared PMAAc−cellulase with a new UCST of 19 °C exhibited significantly improved pH, temperature, storage, and operation stabilities compared with that of free catalyst, and about 82.4% of its original activity was retained even after ten cycles. Cellulase systems containing endo-β-1,4-glucanase (EG), cellobiohydrolase (CBH), and βglucosidase (β-G) are coimmobilized at an optimum ratio on PMAAc by adjusting the additive amount of β-G, which can obtain higher hydrolysis efficiency. It was found that the coimmobilization of cellulase and β-glucosidase at the optimum ratio of 2.5:1 (w/w) showed excellent performance for the hydrolysis of cellulose, and the yield of glucose was up to 89.1% at 50 °C (>UCST) after 24 h, which was 58.4% and 15.4% higher than that of PMAAc−cellulase and free cellulase and β-glucosidase, respectively. The coimmobilized PMAAc−cellulase and β-glucosidase still retained 61.48% of its original productivity after eight cycles of hydrolysis. This novel UCST-type polymer−enzyme catalytic system displays great potential in cellulose biorefining.

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