We demonstrate experimental data to elucidate the reason for the discrepancies of reported band gap energy (Eg) of Cu2ZnSnSe4 (CZTSe) thin films, i.e., 1.0 or 1.5 eV. Eg of the coevaporated CZTSe film synthesized at substrate temperature (Tsub) of 370 °C, which was apparently phase pure CZTSe confirmed by x-ray diffraction (XRD) and Raman spectroscopy, is found to be around 1 eV regardless of the measurement techniques. However, depth profile of the same sample reveals the formation of ZnSe at CZTSe/Mo interface. On the other hand, Eg of the coevaporated films increases with Tsub due to the ZnSe formation, from which we suggest that the existence of ZnSe, which is hardly distinguishable from CZTSe by XRD, is the possible reason for the overestimation of overall Eg.

Nitrous oxide (N 2 O) is a potent greenhouse gas with a strong potential to drive climate change (1, 2) and will continue to be the largest contributor to ozone depletion in the stratosphere (2, 3). Anthropogenic activities, predominantly, fertilizer application in agricultural production, have contributed to a steady increase in atmospheric N 2 O concentrations, and a continued upward trend is expected (4-6). Particularly troublesome are the findings of a recent study that concluded that without solutions for the N 2 O problem, carbon dioxide (CO 2 ) emission reductions even greater than those already proposed will be required to avoid climate change (7). Due to its environmental impact, the pathways leading to the generation and consumption of N 2 O have received heightened interest.In the environment, N 2 O is predominantly formed as an intermediate of denitrification and a nitrification by-product (8). Denitrification is the stepwise reduction of NO 3 Ϫ /NO 2 Ϫ to gaseous products (i.e., N 2 O, N 2 ), with each step being mediated by distinct enzyme systems (9). A kinetic imbalance in the rates of reactions producing and consuming N 2 O during denitrification leads to the release of N 2 O to the atmosphere (8, 10). In nitrification, N 2 O is generated by nitrifier denitrification and as a byproduct of ammonia oxidation (8,11,12). A recent report indicated that nitrifiers, rather than denitrifiers, may be the primary source of N 2 O in agricultural soils (12). Other processes contributing to N 2 O formation include respiratory ammonification (also known as dissimilatory nitrate/nitrite reduction to ammonium [DNRA]) and chemodenitrification (i.e., the abiotic reaction of NO 2 Ϫ with ferrous iron) (13,14). In contrast to the diverse pathways of N 2 O generation, the only known major biological pathway for the removal of N 2 O is by reduction to N 2 , catalyzed by the enzyme nitrous oxide reductase (NosZ) (8,(15)(16)(17)

N 2 O-reducing organisms with nitrous oxide reductases (NosZ) are known as the only biological sink of N 2 O in the environment. Among the most abundant nosZ genes found in the environment are nosZ genes affiliated with the understudied Gemmatimonadetes phylum. In this study, a unique regulatory mechanism of N 2 O reduction in Gemmatimonas aurantiaca strain T-27, an isolate affiliated with the Gemmatimonadetes phylum, was examined. Strain T-27 was incubated with N 2 O and/or O 2 as the electron acceptor. Significant N 2 O reduction was observed only when O 2 was initially present. When batch cultures of strain T-27 were amended with O 2 and N 2 O, N 2 O reduction commenced after O 2 was depleted. In a long-term incubation with the addition of N 2 O upon depletion, the N 2 O reduction rate decreased over time and came to an eventual stop. Spiking of the culture with O 2 resulted in the resuscitation of N 2 O reduction activity, supporting the hypothesis that N 2 O reduction by strain T-27 required the transient presence of O 2 . The highest level of nosZ transcription (8.97 nosZ transcripts/recA transcript) was observed immediately after O 2 depletion, and transcription decreased ϳ25-fold within 85 h, supporting the observed phenotype. The observed difference between responses of strain T-27 cultures amended with and without N 2 O to O 2 starvation suggested that N 2 O helped sustain the viability of strain T-27 during temporary anoxia, although N 2 O reduction was not coupled to growth. The findings in this study suggest that obligate aerobic microorganisms with nosZ genes may utilize N 2 O as a temporary surrogate for O 2 to survive periodic anoxia.IMPORTANCE Emission of N 2 O, a potent greenhouse gas and ozone depletion agent, from the soil environment is largely determined by microbial sources and sinks. N 2 O reduction by organisms with N 2 O reductases (NosZ) is the only known biological sink of N 2 O at environmentally relevant concentrations (up to ϳ1,000 parts per million by volume [ppmv]). Although a large fraction of nosZ genes recovered from soil is affiliated with nosZ found in the genomes of the obligate aerobic phylum Gemmatimonadetes, N 2 O reduction has not yet been confirmed in any of these organisms. This study demonstrates that N 2 O is reduced by an obligate aerobic bacterium, Gemmatimonas aurantiaca strain T-27, and suggests a novel regulation mechanism for N 2 O reduction in this organism, which may also be applicable to other obligate aerobic organisms possessing nosZ genes. We expect that these findings will significantly advance the understanding of N 2 O dynamics in environments with frequent transitions between oxic and anoxic conditions.

No abstract

Methanotrophs synthesize methanobactin, a secondary metabolite that binds copper with an unprecedentedly high affinity. Such a strategy may provide methanotrophs a "copper monopoly" that can inhibit the activity of copper-containing enzymes of other microbes, e.g., copper-dependent NO reductases. Here, we show that methanobactin from Methylosinus trichosporium OB3b inhibited NO reduction in denitrifiers. When Pseudomonas stutzeri DCP-Ps1 was incubated in cocultures with M. trichosporium OB3b or with purified methanobactin from M. trichosporium OB3b, stoichiometric NO production was observed from NO reduction, whereas no significant NO accumulation was observed in cocultures with a mutant defective in methanobactin production. Copper uptake by P. stutzeri DCP-Ps1 was inhibited by the presence of purified methanobactin, leading to a significant downregulation of nosZ transcription. Similar findings were observed with three other denitrifier strains. These results suggest that in situ stimulation of methanotrophs can inadvertently increase NO emissions, with the potential for increasing net greenhouse gas emissions.

No abstract

The nitroheterocyclic 3-nitro-1,2,4-triazol-5-one (NTO) is an ingredient of insensitive explosives increasingly used by the military, becoming an emergent environmental pollutant. Cometabolic biotransformation of NTO occurs in mixed microbial cultures in soils and sludges with excess electron-donating substrates. Herein, we present the unusual energy-yielding metabolic process of NTO respiration, in which the NTO reduction to 3-amino-1,2,4-triazol-5-one (ATO) is linked to the anoxic acetate oxidation to CO2 by a culture enriched from municipal anaerobic digester sludge. Cell growth was observed simultaneously with NTO reduction, whereas the culture was unable to grow in the presence of acetate only. Extremely low concentrations (0.06 mg L–1) of the uncoupler carbonyl cyanide m-chlorophenyl hydrazone inhibited NTO reduction, indicating that the process was linked to respiration. The ultimate evidence of NTO respiration was adenosine triphosphate production due to simultaneous exposure to NTO and acetate. Metagenome sequencing revealed that the main microorganisms (and relative abundances) were Geobacter anodireducens (89.3%) and Thauera sp. (5.5%). This study is the first description of a nitroheterocyclic compound being reduced by anaerobic respiration, shedding light on creative microbial processes that enable bacteria to make a living reducing NTO.

The BNP concentration used for the diagnosis of CHF in Korean people is considerably higher than the normal cut-off value of 100 pg/mL. In the non-CHF patients, the BNP values of women were influenced less by underlying disease. This suggests that the factors that influence BNP values in women are different from those in men.