BackgroundAnaerobic, mesophilic, and cellulolytic Clostridium papyrosolvens produces an efficient cellulolytic extracellular complex named cellulosome that hydrolyzes plant cell wall polysaccharides into simple sugars. Its genome harbors two long cellulosomal clusters: cip-cel operon encoding major cellulosome components (including scaffolding) and xyl-doc gene cluster encoding hemicellulases. Compared with works on cip-cel operon, there are much fewer studies on xyl-doc mainly due to its rare location in cellulolytic clostridia. Sequence analysis of xyl-doc revealed that it harbors a 5′ untranslated region (5′-UTR) which potentially plays a role in the regulation of downstream gene expression. Here, we analyzed the function of 5′-UTR of xyl-doc cluster in C. papyrosolvens in vivo via transformation technology developed in this study.ResultsIn this study, we firstly developed an electrotransformation method for C. papyrosolvens DSM 2782 before the analysis of 5′-UTR of xyl-doc cluster. In the optimized condition, a field with an intensity of 7.5–9.0 kV/cm was applied to a cuvette (0.2 cm gap) containing a mixture of plasmid and late cell suspended in exponential phase to form a 5 ms pulse in a sucrose-containing buffer. Afterwards, the putative promoter and the 5′-UTR of xyl-doc cluster were determined by sequence alignment. It is indicated that xyl-doc possesses a long conservative 5′-UTR with a complex secondary structure encompassing at least two perfect stem-loops which are potential candidates for controlling the transcriptional termination. In the last step, we employed an oxygen-independent flavin-based fluorescent protein (FbFP) as a quantitative reporter to analyze promoter activity and 5′-UTR function in vivo. It revealed that 5′-UTR significantly blocked transcription of downstream genes, but corn stover can relieve its suppression.ConclusionsIn the present study, our results demonstrated that 5′-UTR of the cellulosomal xyl-doc cluster blocks the transcriptional activity of promoter. However, some substrates, such as corn stover, can relieve the effect of depression of 5′-UTR. Thus, it is speculated that 5′-UTR of xyl-doc was a putative riboswitch to regulate the expression of downstream cellulosomal genes, which is helpful to understand the complex regulation of cellulosome.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1040-0) contains supplementary material, which is available to authorized users.
A flower-like metallic Bi-modified Bi2WO6/BiOI heterojunction was fabricated by a two-step approach of hydrothermal method and in situ ethylene glycol reduction method. The ternary system was confirmed by structural analysis and surface and morphological studies. Compared with Bi2WO6, BiOI, and their binary nanomaterials, the catalyst exhibits excellent photocatalytic performance for the degradation of ciprofloxacin (CIP) and levofloxacin (LEV) under visible light irradiation. The improvement of photocatalytic performance was ascribed to the synergistic effect between metal Bi nanoparticles and Bi2WO6/BiOI p-n heterojunction, which enhanced the light absorption capacity and the separation efficiency of photogenerated carriers. By studying the effect of solution pH on CIP degradation, it was found that when pH = 10 , the degradation efficiency of the catalyst on ciprofloxacin reached 100% within 40 min. It provides a new idea for the design and synthesis of ternary photocatalysts for purification of alkaline domestic sewage.
Roscoea tibetica is a most widespread and extensively phenotypic-variable alpine ginger species. Here, we reported the complete chloroplast (cp) genome sequence of R. tibetica. The complete chloroplast genome is 163,515 base pairs (bp) in length, containing two inverted repeat (IRa and IRb) regions of 29,781 bp, which was separated by a large single-copy (LSC) region of 88,090 bp and a small singlecopy (SSC) region of 15,863 bp. The overall GC content of the plastid genome was 36.06%. In total, 113 unique genes were annotated, including 79 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. Phylogenetic analysis based on 22 chloroplast genomes indicates that R. tibetiaca is closely related to R. humeana, forming a monophyletic group with high value.
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