Trifluoromethyl Rhodium-Carbynoid in [2+1+2] Cycloadditions.

Trifluoromethyl cationic carbyne (CF3 C+ :) possessing dual carbene-carbocation behavior emulated as trifluoromethyl metal-carbynoid (CF3 C+ =M) has not been explored yet, and its reaction characteristics are unknown. Herein, a novel α-diazotrifluoroethyl sulfonium salt was prepared and used in Rh-catalyzed three-component [2+1+2] cycloadditions for the first time with commercially available N-fused heteroarenes and nitriles, yielding a series of imidazo[1,5-a] N-heterocycles that are of interest in medicinal chemistry, in which the insertion of trifluoromethyl Rh-carbynoid (CF3 C+ =Rh) into C=N bonds of N-fused heteroarenes was involved. This strategy demonstrates synthetic applications in late-stage modification of pharmaceuticals, construction of CD3 -containing N-heterocycles, gram-scale experiments, and synthesis of phosphodiesterase 10A inhibitor analog. These highly valuable and modifiable imidazo[1,5-a] N-heterocycles exhibit good antitumor activity in vitro, thus demonstrating their potential applications in medicinal chemistry.

Phenol degradation and genotypic analysis of dioxygenase genes in bacteria isolated from sediments

Abstract The aerobic degradation of aromatic compounds by bacteria is performed by dioxygenases. To show some characteristic patterns of the dioxygenase genotype and its degradation specificities, twenty-nine gram-negative bacterial cultures were obtained from sediment contaminated with phenolic compounds in Wuhan, China. The isolates were phylogenetically diverse and belonged to 10 genera. All 29 gram-negative bacteria were able to utilize phenol, m-dihydroxybenzene and 2-hydroxybenzoic acid as the sole carbon sources, and members of the three primary genera Pseudomonas, Acinetobacter and Alcaligenes were able to grow in the presence of multiple monoaromatic compounds. PCR and DNA sequence analysis were used to detect dioxygenase genes coding for catechol 1,2-dioxygenase, catechol 2,3-dioxygenase and protocatechuate 3,4-dioxygenase. The results showed that there are 4 genotypes; most strains are either PNP (catechol 1,2-dioxygenase gene is positive, catechol 2,3-dioxygenase gene is negative, protocatechuate 3,4-dioxygenase gene is positive) or PNN (catechol 1,2-dioxygenase gene is positive, catechol 2,3-dioxygenase gene is negative, protocatechuate 3,4-dioxygenase gene is negative). The strains with two dioxygenase genes can usually grow on many more aromatic compounds than strains with one dioxygenase gene. Degradation experiments using a mixed culture representing four bacterial genotypes resulted in the rapid degradation of phenol. Determinations of substrate utilization and phenol degradation revealed their affiliations through dioxygenase genotype data.

Phenol degradation and genotypic analysis of dioxygenase genes in bacteria isolated from sediments.

The aerobic degradation of aromatic compounds by bacteria is performed by dioxygenases. To show some characteristic patterns of the dioxygenase genotype and its degradation specificities, twenty-nine gram-negative bacterial cultures were obtained from sediment contaminated with phenolic compounds in Wuhan, China. The isolates were phylogenetically diverse and belonged to 10 genera. All 29 gram-negative bacteria were able to utilize phenol, m-dihydroxybenzene and 2-hydroxybenzoic acid as the sole carbon sources, and members of the three primary genera Pseudomonas, Acinetobacter and Alcaligenes were able to grow in the presence of multiple monoaromatic compounds. PCR and DNA sequence analysis were used to detect dioxygenase genes coding for catechol 1,2-dioxygenase, catechol 2,3-dioxygenase and protocatechuate 3,4-dioxygenase. The results showed that there are 4 genotypes; most strains are either PNP (catechol 1,2-dioxygenase gene is positive, catechol 2,3-dioxygenase gene is negative, protocatechuate 3,4-dioxygenase gene is positive) or PNN (catechol 1,2-dioxygenase gene is positive, catechol 2,3-dioxygenase gene is negative, protocatechuate 3,4-dioxygenase gene is negative). The strains with two dioxygenase genes can usually grow on many more aromatic compounds than strains with one dioxygenase gene. Degradation experiments using a mixed culture representing four bacterial genotypes resulted in the rapid degradation of phenol. Determinations of substrate utilization and phenol degradation revealed their affiliations through dioxygenase genotype data.

[Antioxidative function of katG gene in Rhizobium leguminosarum].

OBJECTIVE: Catalase-peroxidase KatG can protect bacteria from damage of reactive oxygen species. This study investigated the antioxidative function of catalase - peroxidase gene katG in Rhizobium leguminosarum 3841. METHODS: katG mutant strain of R. leguminosarum was constructed by homologous recombination. The wild type, katG mutant and complementary strain were challenged by oxidative stress and symbiotic ability. RESULTS: Under free - living conditions, the katG mutant exhibited no generation time extension. However, cells of the katG strain were deficient in consumption oj high concentrations of H2O2and were vulnerable after aquick exposure to H2O2. The real-time qRT-PCR results showec that katG was expressed independently of exogenous H2O2. In contrast, the katG mutant strain displayed higher expres, level of ohrB gene and lower expression level of grxC than the wild type. With regard to symbiotic capacities with Pisum sativum, the katG mutant was indistinguishable in root nodule nitrogenase activity and competition nodule ability from the wild type. However, katG gene was expressed significantly lower in bacteroids than that in free-living strains. Besides, the colonization of the pea rhizosphere by the katG mutant was impaired compared to that of the wild type. CONCLUSION: ThE deletion of katG had nosignificant effect in 3841 under the free-living and symbiosis condition but was essential ir antioxidation and colonization of the pea rhizosphere. Although katG could not be induced by H2O2, it still played acentra role in antioxidation and symbiotic nitrogen fixation by regulating the antioxidant genes such as ohrB and grxC.

Paenibacillus enshidis sp. nov., Isolated from the Nodules of Robinia pseudoacacia L.

A Gram-positive, motile, endospore-forming, rod-shaped bacterium, designated RP-207(T), was isolated from the nodules of Robinia pseudoacacia L. plants planted in Enshi District, Hubei, PR China. Phylogenetic analyses based on the 16S rRNA gene sequence showed that the novel strain was affiliated to the genus Paenibacillus, with its closest relatives being Paenibacillus xylanilyticus XIL14(T) (95.6%), Paenibacillus peoriae DSM8320(T) (95.3%) and Paenibacillus polymyxa DSM 36(T) (95.3%). The DNA G+C content was 47.0 mol%. DNA-DNA hybridization value between strain RP-207(T) and P. xylanilyticus XIL14(T) was 40.1%. The diamino acid found in the cell wall peptidoglycan was meso-diaminopimelic. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unidentified amino-phospholipid and an unknown phospholipid. The predominant menaquinone was menaquinone-7 (MK-7), and the major fatty acid was anteiso-C15:0 and C16:0. On the basis of its physiological and biochemical characteristics and the level of DNA-DNA hybridization, strain RP-207(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus enshidis sp. nov. is proposed. The type strain is RP-207(T) (=CCTCC AB 2013275(T) = KCTC 33519(T)).