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CRISPR-associated transposons (CASTs) exist in different groups of bacteria, including certain cyanobacteria, which contain type V-K CAST systems. These systems contain genes encoding Tn7-like transposase subunits and a divergent number of cargo genes. How the activity of these systems is controlled in situ has remained largely unknown but possibly regulatory genes within these elements are prime candidates. Deletion of the respective regulator gene alr3614 in the cyanobacterium Anabaena (Nostoc) sp. PCC 7120 led to the overexpression of CRISPR tracrRNA, precursor crRNAs and mRNAs encoding the Cas12k effector protein (all3613) and Tn7-like transposase subunits. Upon complementation, these same genes were repressed again. DNase I footprinting and electrophoretic mobility shift assays verified the direct interaction between Alr3614 and the promoter of cas12k and identified a widely conserved binding motif. Structural analysis of Alr3614 at 1.5 Å resolution revealed that it belongs to the MerR-type transcription factor family but with distinct dimerization and effector-binding domains. This protein assembles into a homodimer interacting with DNA through its N-terminal winged helix-turn-helix (wHTH) domain and binds an effector molecule through a C-terminal α-helical domain lacking a conserved cysteine. These results identify Alr3614 as a transcriptional repressor of the CAST system in Anabaena sp. PCC 7120. We suggest naming this family of repressors CvkR for Cas V-K repressors, which are at the core of a widely conserved regulatory mechanism that controls type V-K CAST systems.

To accurately explore the interaction mechanism between Escherichia coli and Staphylococcus aureus, we designed an ecological experiment to monoculture and co-culture E. coli and S. aureus. We co-cultured 45 strains of E. coli and S. aureus, as well as each species individually to measure growth over 36 h. We implemented a genome wide association study (GWAS) based on growth parameters (λ, R, A and s) to identify significant single nucleotide polymorphisms (SNPs) of the bacteria. Three commonly used growth regression equations, Logistic, Gompertz, and Richards, were used to fit the bacteria growth data of each strain. Then each equation’s Akaike’s information criterion (AIC) value was calculated as a commonly used information criterion. We used the optimal growth equation to estimate the four parameters above for strains in co-culture. By plotting the estimates for each parameter across two strains, we can visualize how growth parameters respond ecologically to environment stimuli. We verified that different genotypes of bacteria had different growth trajectories, although they were the same species. We reported 85 and 52 significant SNPs that were associated with interaction in E. coli and S. aureus, respectively. Many significant genes might play key roles in interaction, such as yjjW, dnaK, aceE, tatD, ftsA, rclR, ftsK, fepA in E. coli, and scdA, trpD, sdrD, SAOUHSC_01219 in S. aureus. Our study illustrated that there were multiple genes working together to affect bacterial interaction, and laid a solid foundation for the later study of more complex inter-bacterial interaction mechanisms.

Objective: The clinical efficacy and safety of verapamil combined with anti-tumor drugs through pleural perfusion in the malignant pleural effusion(MPE) were observed. Methods: From January 2013 to June 2019, 79 patients with MPE were randomized. There were 37 cases in control group and 42 cases in the treatment group. After MPE were completely drained, anti-tumor drugs or verapamil combined with anti-tumor drugs were perfused through indwelling pleural catheters(IPCs). In the control group: interleukin-2(IL-2) 3M units and cisplatin; In the treatment group: IL-2 3M units, cisplatin and verapamil. After 1 cycle of treatment, the clinical efficacy and toxic side response were evaluated as well as median survival and overall survival. Results: After treatment, 2 cases acquired complete remission (CR) and 17 cases acquired partial remission (PR). The efficacy (CR add PR) was 51.35% in the control group; 6 cases acquired CR and 28 cases acquired PR. The efficacy (CR add PR) was 80.95% in the treatment group; The efficacy was significantly different in the two group (p). Median survival was 4 months in the control group and 13 months in treatment group. The over survival(OS) was significantly different in the two group (p). After verapamib combined with chemotherapy were perfused, the patient had appeared Ⅰ~Ⅱ degree reaction and all were relieved in a short period of time. Among them, 17 cases appeared leukopenia (40.47%), 23 cases had nausea and vomiting (54.76%), 10 cases appeared diarrhea (23.80%), 6 cases appeared had hair loss (14.28%), 19 cases appeared fever (45.23%), 9 cases appeared liver impairment (21.42%). The toxic side reactions and adverse cardiovascular effects in treatment group was no significant different from them of in the control group. Conclusion: The therapy of verapamil combined with anti-tumor drugs through IPC is effective and safe in the MEP.

In recent years, the emergence of next generation sequencing (NGS) makes it possible to obtain the data of microbial genome accurately in a short period of time, and it has become a powerful tool for microbial molecular ecology research. NGS has the advantage of non-sequence dependence and it can simultaneously detect nearly all culturable and non-culturable microorganisms which have high or low contents. With the explosion of sequencing data generated by NGS and multi-omics techniques, there is a growing need for the powerful genetic statistical models to generate meaningful hypotheses about the mechanisms underlying biological interaction. In this paper, we mainly discuss the application and prospect of NGS combined with the genetic statistical models in microbial molecular ecology. The combination of the two in promoting the study of microbial interspecific interaction is discussed. Then we analyze the application of the combination in the study of bacterial phenotypic plasticity. Finally, we describe its application in constructing gene regulatory network of microbe-plant interaction, which aims to identify key genes to enhance the disease resistance of plants.

The lovastatin hydrolase PcEST from the fungus Penicillium chrysogenum exhibits enormous potential for industrial-scale applications in single-step production of monacolin J, the key precursor for synthesis of the cholesterol-lowering drug simvastatin. This enzyme specifically and efficiently catalyzes the conversion of lovastatin to monacolin J but cannot hydrolyze simvastatin. Understanding the catalytic mechanism and the structure–function relationship of PcEST is therefore important for further lovastatin hydrolase screening, engineering, and commercial applications. Here, we solved four X-ray crystal structures, including apo PcEST (2.3 Å), PcEST in complex with monacolin J (2.48 Å), PcEST complexed with the substrate analog simvastatin (2.4 Å), and an inactivated PcEST variant (S57A) with the lovastatin substrate (2.3 Å). Structure-based biochemical analyses and mutagenesis assays revealed that the Ser57 (nucleophile)–Tyr170 (general base)–Lys60 (general acid) catalytic triad, the hydrogen-bond network (Trp344 and Tyr127) around the active site, and the specific substrate-binding tunnel together determine efficient and specific lovastatin hydrolysis by PcEST. Moreover, steric effects on nucleophilic attack caused by the 2′,2-dimethybutyryl group of simvastatin resulted in no activity of PcEST on simvastatin. On the basis of structural comparisons, we propose several indicators to define lovastatin esterases. Furthermore, using structure-guided enzyme engineering, we developed a PcEST variant, D106A, having improved solubility and thermostability, suggesting a promising application of this variant in industrial processes. To our knowledge, this is the first report describing the mechanism and structure–function relationship of lovastatin hydrolase and providing insights that may guide rapid screening and engineering of additional lovastatin esterase variants.

Hyperspectral imagery has been widely used in precision agriculture due to its rich spectral characteristics. With the rapid development of remote sensing technology, the airborne hyperspectral imagery shows detailed spatial information and temporal flexibility, which open a new way to accurate agricultural monitoring. To extract crop types from the airborne hyperspectral images, we propose a fine classification method based on multi-feature fusion and deep learning. In this research, the morphological profiles, GLCM texture and endmember abundance features are leveraged to exploit the spatial information of the hyperspectral imagery. Then, the multiple spatial information is fused with the original spectral information to generate classification result by using the deep neural network with conditional random field (DNN+CRF) model. Specifically, the deep neural network (DNN) is a deep recognition model which can extract depth features and mine the potential information of data. As a discriminant model, conditional random field (CRF) considers both spatial and contextual information to reduce the misclassification noises while keeping the object boundaries. Moreover, three multiple feature fusion approaches, namely feature stacking, decision fusion and probability fusion, are taken into account. In the experiments, two airborne hyperspectral remote sensing datasets (Honghu dataset and Xiong’an dataset) are used. The experimental results show that the classification performance of the proposed method is satisfactory, where the salt and pepper noise is decreased, and the boundary of the ground object is preserved.

UAV hyperspectral imagery has been widely applied in the fine classification of crops because of its high spectral resolution and high spatial resolution. As the crops in hyperspectral image show complicated characteristics, only the spectral information is insufficient to distinguish them. Therefore, we use multiple feature fusion method for fine classification of crops in UAV hyperspectral imagery. In our work, the GLCM texture, morphological profile, and endmember abundance feature, are extracted. Meanwhile, three fusion strategies, namely decision fusion, probability fusion, and stacking fusion, are employed to obtain the classification results. The experimental results illustrate the superiority of the multiple fusion approaches in the crop fine classification with hyperspectral imagery.

Background: To understand the willingness of nurses from Tangshan City to undergo Coronavirus disease 2019 (COVID-19) vaccination and identify its influencing factors.Methods: In January 2021, 255 nurses from five medical institutions across Tangshan City were investigated through convenience sampling on a network platform of Sojump. Furthermore, SPSS Statistics v24.0 software was used for general descriptive analysis, rank-sum test and binary logistic regression analysis to analyse willingness rates for COVID-19 vaccination and corresponding influencing factors.Results: A total of 255 valid questionnaires were collected (recovery rate, 85.71%). Among the 255 nurses surveyed, the willingness rate was 67.8%. The major reasons for willingness to undergo COVID-19 vaccination included a high-risk work environment necessitating COVID-19 vaccination (87.9%), expected benefits to themselves and others (72.8%) and worries regarding COVID-19 infection (66.5%). Meanwhile, reasons for unwillingness to undergo COVID-19 vaccination in 82 nurses included concerns regarding safety (89.0%), effectiveness (62.2%) and the possibility of fake vaccines (32.9%). Furthermore, among the 255 nurses, 43.9% were willing to recommend COVID-19 vaccination (n = 112), with the main reasons being prevention of COVID-19 infection (100.0%) and herd immunity via universal vaccination (90.2%). Moreover, the main reasons for unwillingness to recommend COVID-19 vaccination included poor popularity and wait-and-see attitude (85.3%) and hesitancy to recommend given the absence of COVID-19 vaccines (67.1%). With regard to attitude towards COVID-19 vaccine marketing, 149 (58.5%) nurses expressed favour, 101 (39.6%) nurses took a neutral position and 5 (1.9%) expressed displeasure. Univariate analysis revealed that male nurses, as well as those who actively inquired and sought information on COVID-19 vaccines, had significantly higher willingness for vaccination compared to female nurses and those not actively seeking information (P < 0.05). Meanwhile, binary logistic regression analysis indicated that gender, degree of education, working years and active inquiry or search for vaccine information were associated with willingness for COVID-19 vaccination (P < 0.05).Conclusion: This study highlights the need for further improving the willingness of nurses from Tangshan City to undergo and recommend COVID-19 vaccination. Relevant departments should therefore publicise information regarding COVID-19 vaccines for medical staff to ensure the safe and effective promotion thereof.

Additional file 5: Table S4. Fitting R2 of growth curves in E. coli and S. aureus in co-culture.

Salinity is one of the most important abiotic factors in various natural habitats of microbes. Cyanobacteria are the most widely distributed family of photosynthetic microorganisms in environments with fluctuating salinity. In response to salt stress, many cyanobacteria de novo synthesize compatible solutes to maintain osmotic balance in the cell. However, the regulation of intracellular accumulation of these compounds is still not well understood. The freshwater cyanobacterium Synechococcus elongatus PCC 7942 (Syn7942) exclusively accumulates sucrose as a compatible solute upon salt stress and is thus an ideal model microorganism for studying the metabolism of compatible solute dynamics. Here, we focused on elucidating the regulatory mechanisms involved in salt-induced sucrose accumulation in Syn7942. Using a series of physiological and biochemical experiments, we showed that the ionic effect of salt stress plays an important role in inducing sucrose synthesis, whereby elevated ion concentration directly activates the sucrose-synthesizing enzyme sucrose-phosphate synthase and simultaneously inhibits the sucrose-degrading enzyme invertase, resulting in a rapid sucrose accumulation. Thus, we propose a novel mechanism for cyanobacterial adaption to salt stress and fluctuating salinity, i.e., the ion-induced synergistic modulation of the enzymes synthesizing and degrading compatible solutes. These findings greatly enhance our current understanding of microbial adaptation to salt.IMPORTANCE Most microbes de novo synthesize compatible solutes for adaptation to salt stress or fluctuating salinity environments. However, to date, one of the core questions involved in these physiological processes, i.e., the regulation of salt-induced compatible solute biosynthesis, is still not well understood. Here, this issue was systematically investigated by employing the model freshwater cyanobacterium Synechococcus elongatus PCC 7942. A novel mechanism for cyanobacterial adaption to salt stress and fluctuating salinity, i.e., the ion-induced synergistic modulation of key synthesizing and degrading enzymes of compatible solutes, is proposed. Because the ion-induced activation/inhibition of enzymes is a fast and efficient process, it may represent a common strategy of microbes for adaptation to environments with fluctuating salinity.

Salinity is one of the most important abiotic factors in various natural habitats of microbes. Cyanobacteria are the most widely distributed family of photosynthetic microorganisms in environments with fluctuating salinity. In response to salt stress, many cyanobacteria de novo synthesize compatible solutes to maintain osmotic balance in the cell. However, the regulation of intracellular accumulation of these compounds is still not well understood. The freshwater cyanobacterium Synechococcus elongatus PCC 7942 (Syn7942) exclusively accumulates sucrose as a compatible solute upon salt stress and is thus an ideal model microorganism for studying the metabolism of compatible solute dynamics. Here, we focused on elucidating the regulatory mechanisms involved in salt-induced sucrose accumulation in Syn7942. Using a series of physiological and biochemical experiments, we showed that the ionic effect of salt stress plays an important role in inducing sucrose synthesis, whereby elevated ion concentration directly activates the sucrose-synthesizing enzyme sucrose-phosphate synthase and simultaneously inhibits the sucrose-degrading enzyme invertase, resulting in a rapid sucrose accumulation. Thus, we propose a novel mechanism for cyanobacterial adaption to salt stress and fluctuating salinity, i.e., the ion-induced synergistic modulation of the enzymes synthesizing and degrading compatible solutes. These findings greatly enhance our current understanding of microbial adaptation to salt. IMPORTANCE Most microbes de novo synthesize compatible solutes for adaptation to salt stress or fluctuating salinity environments. However, to date, one of the core questions involved in these physiological processes, i.e., the regulation of salt-induced compatible solute biosynthesis, is still not well understood. Here, this issue was systematically investigated by employing the model freshwater cyanobacterium Synechococcus elongatus PCC 7942. A novel mechanism for cyanobacterial adaption to salt stress and fluctuating salinity, i.e., the ion-induced synergistic modulation of key synthesizing and degrading enzymes of compatible solutes, is proposed. Because the ion-induced activation/inhibition of enzymes is a fast and efficient process, it may represent a common strategy of microbes for adaptation to environments with fluctuating salinity.

Background: Patients are often not actively involved in their acute pain management.Objectives: To understand the attitudes of patients, family caregivers and nurses to patient participation in pain management after their knee or hip joint replacement.Design: Q-methodological design.Methods: 45 participants were recruited, included 15 patients, 15 caregivers and 15 nurses. Forty-nine statements were rank-ordered in a Q-sort table.Results: Four factors which explained 65% of the variance were identified from factor analysis. They are named "Endurers", "Supporters", "Worriers" ,and "Wabblers".Conclusion: Each group have a significant knowledge deficit in pain management. Patients and caregivers were more likely to have a passive attitude and false cognition towards pain and analgesic drugs. Nurses often play a role as a supporter, however, it is hard for them to understand their important role in facilitating patient involvement in their pain management.

Monacolin J is a key precursor for the synthesis of simvastatin (Zocor), an important drug for treating hypercholesterolemia. Industrially, monacolin J is manufactured through alkaline hydrolysis of lovastatin, a fungal polyketide produced by Aspergillus terreus. Multistep chemical processes for the conversion of lovastatin to simvastatin are laborious, cost expensive and environmentally unfriendly. A biocatalysis process for monacolin J conversion to simvastatin has been developed. However, direct bioproduction of monacolin J has not yet been achieved. Here, we identified a lovastatin hydrolase from Penicillium chrysogenum, which displays a 232-fold higher catalytic efficiency for the in vitro hydrolysis of lovastatin compared to a previously patented hydrolase, but no activity for simvastatin. Furthermore, we showed that an industrial A. terreus strain heterologously expressing this lovastatin hydrolase can produce monacolin J through single-step fermentation with high efficiency, approximately 95% of the biosynthesized lovastatin was hydrolyzed to monacolin J. Our results demonstrate a simple and green technical route for the production of monacolin J, which makes complete bioproduction of the cholesterol-lowering drug simvastatin feasible and promising.

The precise classification of crop types is an important basis of agricultural monitoring and crop protection. With the rapid development of unmanned aerial vehicle (UAV) technology, UAV-borne hyperspectral remote sensing imagery with high spatial resolution has become the ideal data source for the precise classification of crops. For precise classification of crops with a wide variety of classes and varied spectra, the traditional spectral-based classification method has difficulty in mining large-scale spatial information and maintaining the detailed features of the classes. Therefore, a precise crop classification method using spectral-spatial-location fusion based on conditional random fields (SSLF-CRF) for UAV-borne hyperspectral remote sensing imagery is proposed in this paper. The proposed method integrates the spectral information, the spatial context, the spatial features, and the spatial location information in the conditional random field model by the probabilistic potentials, providing complementary information for the crop discrimination from different perspectives. The experimental results obtained with two UAV-borne high spatial resolution hyperspectral images confirm that the proposed method can solve the problems of large-scale spatial information modeling and spectral variability, improving the classification accuracy for each crop type. This method has important significance for the precise classification of crops in hyperspectral remote sensing imagery.

The removing of hexavalent chromium has received extensive attention. In this work, graphene oxide (GO) was modified by humic acid (HA), then the GO−HA composites were prepared using green methods. The sp2 carbon system was increased markedly and the reduced GO (rGO) that with rough and porous structure was formed in GO−HA composites. GO−HA has a band gap of 2.73 eV and owned an adequate aqueous dispersion. The modification of HA enhanced the performance of GO for Cr(VI) photoreduction at environmental relevant pH. GO−HA could trigger the separation of photo−generated electrons/holes under irradiation with the incident wavelength lower than 455 nm. Wherein rGO sheets, as an electron carrier, allowed photo−excited electrons quickly transferred to Cr(VI) and caused the reduction. The ∙ O 2 - that from the excitation of HA with irradiation also could reduce Cr(VI). Meanwhile, photo−generated holes have ability to combine HA and water molecules. Hence, the depletion of photo−generated electrons and holes would enhance its catalytic ability via the separation of charge carriers. These data indicate that the modification with organic molecules is a convenient strategy to obtain GO−based catalysts, which may pave a way to new developments of the GO−based materials.

Sodium dodecyl sulfate (SDS) is a widely used anionic surfactant in industry and research settings, and is known to have a detrimental effect to the environment. The pathway of SDS degradation by bacteria is initiated by an alkylsulfatase and the oxidized product, 1-dodecanoic acid, subsequently enters into the beta-oxidation pathway and is used as a carbon source. In this work, we solved the crystal structure of Escherichia coli uncharacterized protein YjcS and identified that it belongs to the Type III alkylsulfatase with a signal peptide (residues 1-29) at the N terminus. YjcS hydrolyzed SDS and the double mutant D184N-H185A located in the conserved HXHXDH catalytic motif abolished this activity.

The fine classification of crops is critical for food security and agricultural management. There are many different species of crops, some of which have similar spectral curves. As a result, the precise classification of crops is a difficult task. Although the classification methods that incorporate spatial information can reduce the noise and improve the classification accuracy, to a certain extent, the problem is far from solved. Therefore, in this paper, the method of spatial–spectral fusion based on conditional random fields (SSF-CRF) for the fine classification of crops in UAV-borne hyperspectral remote sensing imagery is presented. The proposed method designs suitable potential functions in a pairwise conditional random field model, fusing the spectral and spatial features to reduce the spectral variation within the homogenous regions and accurately identify the crops. The experiments on hyperspectral datasets of the cities of Hanchuan and Honghu in China showed that, compared with the traditional methods, the proposed classification method can effectively improve the classification accuracy, protect the edges and shapes of the features, and relieve excessive smoothing, while retaining detailed information. This method has important significance for the fine classification of crops in hyperspectral remote sensing imagery.

It is important to obtain abundant sugar feedstocks economically and sustainably for bio-fermentation industry, especially for producing cheap biofuels and biochemicals. Besides plant biomass, photosynthetic cyanobacteria have also been considered to be potential microbe candidates for sustainable production of carbohydrate feedstocks. As the fastest growing cyanobacterium reported so far, Synechococcus elongatus UTEX 2973 (Syn2973) might have huge potential for bioproduction. In this study, we explored the potentials of this strain as photo-bioreactors for sucrose and glycogen production. Under nitrogen-replete condition, Syn2973 could accumulate glycogen with a rate of 0.75 g L(-1) day(-1) at the exponential phase and reach a glycogen content as high as 51 % of the dry cell weight (DCW) at the stationary phase. By introducing a sucrose transporter CscB, Syn2973 was endowed with an ability to secrete over 94 % sucrose out of cells under salt stress condition. The highest extracellular sucrose productivity reached 35.5 mg L(-1) h(-1) for the Syn2973 strain expressing cscB, which contained the similar amounts of intracellular glycogen with the wild type. Potassium chloride was firstly proved to induce sucrose accumulation as well as sodium chloride in Syn2973. By semi-continuous culturing, 8.7 g L(-1) sucrose was produced by the cscB-expressing strain of Syn2973 in 21 days. These results support that Syn2973 is a promising candidate with great potential for production of sugars.

Additional file 2: Codon-optimized gene sequence PMT1231 from P. marinus MIT 9313.

Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N=3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.

Biosynthesis of simvastatin, the active pharmaceutical ingredient of cholesterol-lowering drug Zocor, has drawn increasing global attention in recent years. Although single-step in vivo production of monacolin J, the intermediate biosynthetic precursor of simvastatin, has been realized by utilizing lovastatin hydrolase (PcEST) in our previous study, about 5% of residual lovastatin is still a problem for industrial production and quality control. In order to improve conversion efficiency and reduce lovastatin residues, modification of PcEST is carried out through directed evolution and a novel two-step high-throughput screening method. The mutant Q140L shows 18-fold improved whole-cell activity as compared to the wild-type, and one fold enhanced catalytic efficiency and 3 degrees C increased T-50(10) over the wild-type are observed by characterizing the purified protein. Finally, the engineered A. terreus strain overexpressing Q140L mutant exhibited the increased conversion efficiency and the reduced lovastatin residues by comparing with A. terreus strain overexpressing the wild-type PcEST, where almost 100% of the produced lovastatin is hydrolyzed to monacolin J. Therefore, this improved microbial cell factory can realize single-step bioproduction of monacolin J in a more efficient way, providing an attractive and eco-friendly substitute over the existing chemical synthetic routes of monacolin J and promoting complete bioproduction of simvastatin at industrial scale.

Toxin YafQ functions as a ribonuclease in the dinJ-yafQ toxin-antitoxin system of Escherichia coli. Antitoxin DinJ neutralizes YafQ-mediated toxicity by forming a stable protein complex. Here, crystal structures of the (DinJ)2-(YafQ)2 complex and the isolated YafQ toxin have been determined. The structure of the heterotetrameric complex (DinJ)2-(YafQ)2 revealed that the N-terminal region of DinJ folds into a ribbon-helix-helix motif and dimerizes for DNA recognition, and the C-terminal portion of each DinJ exclusively wraps around a YafQ molecule. Upon incorporation into the heterotetrameric complex, a conformational change of YafQ in close proximity to the catalytic site of the typical microbial ribonuclease fold was observed and validated. Mutagenesis experiments revealed that a DinJ mutant restored YafQ RNase activity in a tetramer complex in vitro but not in vivo. An electrophoretic mobility shift assay showed that one of the palindromic sequences present in the upstream intergenic region of DinJ served as a binding sequences for both the DinJ-YafQ complex and the antitoxin DinJ alone. Based on structure-guided and site-directed mutagenesis of DinJ-YafQ, we showed that two pairs of amino acids in DinJ were important for DNA binding; the R8A and K16A substitutions and the S31A and R35A substitutions in DinJ abolished the DNA binding ability of the DinJ-YafQ complex.

Study the effect of glycolaldehyde on DNA of mouse spleen lymphocytes.The DNA damage induced by different concentrations of glycolaldehyde was detected using single cell gel electrophoresis assay (SCGE).Glycolaldehyde at 0.01 mmol/L could induce lymphocyte DNA strand breakage and DNA damage rate was 8% and, the average migration distance of DNA was (14.32 +/- 2.84) micron. DNA damage rate and the average migration distance of DNA were increased in a concentration-dependent manner.glycolaldehyde could induce DNA damage in different concentration in this experiment.

Background Propane, a major component of liquid petroleum gas (LPG) derived from fossil fuels, has widespread applications in vehicles, cooking, and ambient heating. Given the concerns about fossil fuel depletion and carbon emission, exploiting alternative and renewable source of propane have become attractive. In this study, we report the construction of a novel propane biosynthetic pathway in Escherichia coli. Results We constructed an aldehyde reductases (ALR)-deprived E. coli strain BW25113(DE3) Δ13 via genetic engineering, which produced sufficient isobutyraldehyde precursors and finally achieved de novo synthesis of propane (91 μg/L) by assembling the engineered valine pathway and cyanobacterial aldehyde-deformylating oxygenase (ADO). Additionally, after extensive screening of ADO mutants generated by engineering the active center to accommodate branched-chain isobutyraldehyde, we identified two ADO mutants (I127G, I127G/A48G) which exhibited higher catalytic activity for isobutyraldehyde and improved propane productivity by three times (267 μg/L). Conclusions The propane biosynthetic pathway constructed here through the engineered valine pathway can produce abundant isobutyraldehyde for ADO and overcome the low availability of precursors in propane production. Furthermore, the rational design aiming at the ADO active center illustrates the plasticity and catalytic potential of ADO. These results together highlight the potential for developing a microbial biomanufacturing platform for propane. Electronic supplementary material The online version of this article (doi:10.1186/s13068-016-0496-z) contains supplementary material, which is available to authorized users.