Cell extracts of butyrate-forming clostridia have been shown to catalyze acetyl-coenzyme A (acetyl-CoA)-and ferredoxin-dependent formation of H 2 from NADH. It has been proposed that these bacteria contain an NADH:ferredoxin oxidoreductase which is allosterically regulated by acetyl-CoA. We report here that ferredoxin reduction with NADH in cell extracts from Clostridium kluyveri is catalyzed by the butyryl-CoA dehydrogenase/Etf complex and that the acetyl-CoA dependence previously observed is due to the fact that the cell extracts catalyze the reduction of acetyl-CoA with NADH via crotonyl-CoA to butyryl-CoA. The cytoplasmic butyryl-CoA dehydrogenase complex was purified and is shown to couple the endergonic reduction of ferredoxin (E 0 ‫؍‬ ؊410 mV) with NADH (E 0 ‫؍‬ ؊320 mV) to the exergonic reduction of crotonyl-CoA to butyryl-CoA (E 0 ‫؍‬ ؊10 mV) with NADH. The stoichiometry of the fully coupled reaction is extrapolated to be as follows: 2 NADH ؉ 1 oxidized ferredoxin ؉ 1 crotonyl-CoA ‫؍‬ 2 NAD ؉ ؉ 1 ferredoxin reduced by two electrons ؉ 1 butyryl-CoA. The implications of this finding for the energy metabolism of butyrate-forming anaerobes are discussed in the accompanying paper.Clostridium kluyveri is a strictly anaerobic gram-positive endospore-forming bacterium (2). Among the clostridia this organism is unique in fermenting ethanol and acetate to butyrate, caproate, and H 2 (38, 49) and in deriving a large portion (30%) of its cell carbon from CO 2 (52). Both its energy metabolism and its pathways of biosynthesis have therefore been the subject of many investigations (26, 39a). In particular, understanding the energy metabolism of C. kluyveri remains a challenge for microbiologists, and one of the pertinent questions is how this organism generates H 2 (36, 39a, 48).

Single-atom catalysts anchoring offers a desirable pathway for efficiency maximization and cost-saving for photocatalytic hydrogen evolution. However, the single-atoms loading amount is always within 0.5% in most of the reported due to the agglomeration at higher loading concentrations. In this work, the highly dispersed and large loading amount (>1 wt%) of copper single-atoms were achieved on TiO2, exhibiting the H2 evolution rate of 101.7 mmol g−1 h−1 under simulated solar light irradiation, which is higher than other photocatalysts reported, in addition to the excellent stability as proved after storing 380 days. More importantly, it exhibits an apparent quantum efficiency of 56% at 365 nm, a significant breakthrough in this field. The highly dispersed and large amount of Cu single-atoms incorporation on TiO2 enables the efficient electron transfer via Cu2+-Cu+ process. The present approach paves the way to design advanced materials for remarkable photocatalytic activity and durability.

Cu single-atom catalysts could be promising non-noble catalysts towards oxygen reduction for fuel cell applications.

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Cultivated soybean ( Glycine max) is an economically important crop that is grown for its oil and protein products. A better knowledge of its genetic diversity will be valuable for the utilization, conservation, and management of germplasm collections. Using the database of the National Germplasm Evaluation Program of China (NGEPC), we studied the geographical distribution of accessions, the genetic diversity of 15 qualitative and quantitative characters, and the genetic diversity centers of cultivated soybean in China using variation in these 15 traits and genetic diversity indexes (Shannon index). Cultivated soybean is widely distributed throughout China. As an indication of its distribution, a line can be roughly drawn from the Daxinganling mountains in northeastern China to the Qingzang plateaus in southwestern China based on the abundance of accessions and locations of the collections. Of the 22,637 known accessions in China, the 20,570 collected over a vast area between latitudes 18 degrees and 53 degrees N and longitudes 80 degrees and 136 degrees E were used in this study. The Shannon indexes of various morphological traits were calculated. Cultivated soybean accessions were found to exhibit a higher genetic diversity in the area between 34 degrees -41 degrees N and 110 degrees -115 degrees E. On the basis of the geographical distribution of a number of accessions, and their genetic diversity, one genetic diversity center-downstream of the Yellow River Valley-is proposed. Based on these results and on Vavilov's theory on crop origins, one possible diversity center was proposed.