Nosiheptide is a typical thiopeptide antibiotic displaying potent activity toward various drug-resistant strains of Gram-positive pathogens.Although nosiheptide lacks in vivo activity, and good water-solubility with a series of uncontrollable analogues, which may limit its clinical application, glycosylated analogues may overcome problem of low activity and may improve its druggability.In search of novel glycosylated nosiheptide producers, we applied a genome mining strategy that identified Actinoalloteichus sp.AHMU CJ021 that contains all genes required.However, despite the presence of a predicted glycosyltransferase, glycosylated derivatives of nosiheptide were not detected, after following one strain many compounds (OSMAC) strategy and heterologous expression of a regulatory protein NocP.Nevertheless, nosiheptide produced by this strain was remarkably pure, and further experiments were conducted to improve its production by optimization of the culture medium.Under optimal conditions, 58.73 mg/L nosiheptide was produced, representing an almost 6-fold improvement compared to the original fermentation medium.Therefore, we consider Actinoalloteichus sp.AHMU CJ021 a suitable potential candidate for industrial production of nosiheptide, which provides the basis for solving the problem of nosiheptide structural analogues.

Objective To investigate the screening strategy of group B streptococcus (GBS) in the reproductive tract of women in the third trimester and analyze its impact on pregnancy outcome. Methods A total of 85 461 pregnant women in 35-37 weeks of gestation from Bao′an Maternity and Child Health Hospital, Jinan University from January 2011 to June 2018 were enrolled. They were divided into 3 periods according to different GBS screening strategies, the unscreened period included 31 384 cases (36.72%), 33 267 cases (38.93%) were included in partial screening period, 20 810 cases (24.35%) were included in screening period. All GBS screening positive pregnant women were given intrapartum antibiotic prophylaxis (IAP). The impact on pregnancy outcomes, and the impact of different GBS collection transport and culture methods on the positive rate of GBS screening were analyzed. Results (1) The incidence of neonatal early onset GBS disease (EOGBSD) in unscreened period was 0.03% (11/31 773), in partial screening period was 0.02%(6/33 887), and in screening period, the incidence of neonatal EOGBSD decreased to 0, the difference was statistically significant (χ2=7.86, P=0.02).(2) The incidence of hematogenous infection of GBS in pregnant women was 0.02%(6/33 887) in partial screening period, and there was none in screening period, there was no significant difference (adjusted χ2=3.75, P=0.05). (3) In the screening period, the positive rate of GBS was 14.08%(2 719/19 306), which was significantly higher than the positive rate of GBS in the partial screening period (11.48%, 2 058/17 920; χ2=56.12, P=0.00). (4) Antibiotic sensitivity tests of 4 777 GBS strains showed that the antibiotics with higher resistance rate were tetracycline (81.52%, 3 896/4 777), erythromycin (66.59%, 3 181/4 777), and clindamycin (64.31%, 3 072/4 777). The combination of erythromycin, clindamycin and tetracycline was the most common resistant pattern, accounting for 48.80% (2 331/4 777). No penicillin, ceftriaxone or vancomycin resistant strains was found. Conclusions GBS screening strategy in different regions could combine the local neonatal EOGBSD incidence rate, maternal GBS colonization rate, and the socioeconomic factors to determine whether universal GBS screening or screening for high-risk maternal women. GBS screening positive rate is related to the population, scope of the investigation, the sample collection, delivery and culture methods. The multi-drug resistance rate of GBS is high.[Key words] Streptococcus agalactiae; Streptococcal infections; Neonatal sepsis; Prenatal diagnosis; Pregnancy trimester, third; Pregnancy outcome

Microbial secondary metabolites have always been one of the important sources of discovery and development of new drugs due to their remarkable biological activities. The explosion of genome sequences has revealed that Streptomyces harbor an immensely untapped biosynthetic potential. However, the number of active secondary metabolites with new skeletons or structural units found from Streptomyces is much lower than that of biosynthetic gene clusters(BGCs), mainly due to the fact that many BGCs are either expressed weakly or transcriptionally silent under conventional laboratory conditions. Beginning with the bioinformatics tools for BGCs prediction, this review focuses on the classical approaches to activate silent BGCs of Streptomyces in native and heterologous hosts. Moreover, several new strategies including transcriptional factors decoy, reporter-guided high-throughput selection and muliplexed CRISPR-TAR were detailed, which provide methodological references for mining new secondary metabolites from Streptomyces.

Mogrosides, the main sweet components isolated from Siraitia grosvenorii, are a family of cucurbitane-type tetracyclic triterpenoid saponins. Given that the high sweetness, low calorie and excellent taste, mogrosides have become the important resource for the development of natural non-nutritive sweeteners. As reported, 11α-hydroxyl group in the structural skeleton of mogrosides was closely related to sweetness and taste, but it had not been confirmed experimentally. In this work, we used mogroside IIIE as a model compound, which was 300 times sweeter than 5% sucrose and tasted better, and modified its 11α-hydroxyl group through glycosyltransferase to elucidate the relations between structure and sweetness of mogroside compounds. The glycosyltransferase HXSW-GT-2 was obtained to regio-selectively glycosylate the 11α-hydroxyl group of mogroside IIIE through the screening of glycosyltransferase library. And then, the soluble expression of HXSW-GT-02 in Escherichia coli was efficiently achieved by optimizing the induction conditions. Subsequently, the yield of glycosylated mogroside IIIE(MG-IIIE-Glu)was increased to > 85% through optimizing reaction pH, temperature, UDP-G dosage and biocatalyst loading. The product MG-IIIE-Glu was bio-prepared at a 0. 5 L scale and the final purity was 97. 8%. A “mouth feel” test showed that MG-IIIE-Glu had no sweetness and displayed obvious bitterness through the comparison with mogroside IIIE and 5% sucrose. In conclusion, the function of the 11α-hydroxyl group of mogrosides in sweetness and taste was preliminarily elucidated which would be beneficial for the structural modification and development of mogroside sweeteners.

The aim was to develop the simple preparation method of mogroside ⅢE,and to lay the foundation for the development of the mogroside sweeteners. In the present study,the glycosidase CPU-GH17,which can regio-selectively biosynthesize mogroside ⅢE from mogroside V,was screened from the established library of glycosi-dases. Then,the soluble expression condition of CPU-GH17 in E. coli was exploited by investigating isopropyl β-D-thiogalactoside (IPTG)concentration,culture temperature and induction time,and 0. 4 mmol/L IPTG,15 °C and 12 h was used as optimal condition. The result showed that mogroside V could be completely converted into mogroside ⅢE under the conditions of pH 6. 0,45 °C,3 U/mL enzyme loading,5 mg/mL substrate concentration for 20 h. In conclusion,a biosynthetic system for the regio-selective preparation of mogroside ⅢE by recombinant CPU-GH17 was successfully established and verified at a preparative scale.

Microbial secondary metabolites have been a major source for drug discovery and development due to their structural novelty and diversity. Microbial secondary metabolites, typically encoded by specific biosynthetic gene cluster(BGC), are non-essential for the growth and propagation of the microbes. Despite the abundant existence of microbes, the majority of them are unculturable under laboratory conditions. Moreover, given that most of the BGCs from culturable microbes are silent, the discovery of novel microbial secondary metabolites has been hampered. Recently, the heterologous expression of BGCs has become an attractive approach to discover various microbial secondary metabolites, among which TAR-based heterologous expression is one of the important tools. This review summarized the principle of TAR, the applications and the advanced strategies of TAR-based methods for heterologous expression of secondary metabolites, which may help the advancements of drug discovery and development from microbial sources.

A new method for determining transaminase activity based on the color change of the reaction solution was established, by using alanine-dependent transaminase VfTA from Vibrio fluvialis JS17 as the research object coupled with pyruvate oxidase and horseradish peroxidase. After the optimization of the conditions, the linear relationship between VfTA activity units and the absorbance at 400 nm was investigated. This method was also applied to determine the activity of commercial transaminase ATA117. The results showed that the detection limit of transaminase VfTA activity was up to 0. 45 U/mL and the detection limit of ATA117 activity was up to 0. 5 U/mL. The transaminase activity could be quickly judged according to the color depth of the reaction solution.

Objective To compare intramedullary nailing assisted by minimally invasive cerclage with simple intramedullary nailing in the treatment of femoral long oblique subtrochanteric fractures.Methods From April 2010 to September 2015,our department treated 39 patients with femoral long oblique subtrochanteric fracture.Of them,16 were treated by cephalomedullary nailing combined with minimally invasive cerclage (observation group of 11 males and 5 females with an average age of 42.8 ± 13.2 years) and 23 by simple cephalomedullary nailing (control group of 17 males and 6 females with an average age of 46.2 ± 10.1 years).Their operation time,intraoperative blood loss,radiologic results (union time and alignment) and functional results [Visual Analog Scale (VAS) and Harris hip score] were compared between the 2 groups.Results The 39 patients were followed up from 12 to 30 months (average,15 months).For the observation group,the varus angle (2.2°± 1.4°) was significantly smaller than for the control group(4.1°±2.2°),the VAS scores at 1 and 3 months postoperatively (3.43 ± 1.54,1.13 ± 1.20) were significantly lower than for the control group (5.61 ± 1.41,3.34 ± 1.82),and the clinical union ratio at 3 months postoperatively(87.5％,14/16) significantly higher than for the control group (47.8％,11/23) (P ＜ 0.05).There were no significant differences between the 2 groups in terms of operation time,intraoperative blood loss,Harris hip score at one year postoperatively,VAS score at 6 months postoperatively,or clinical union ratio at 6 or 12 months postoperatively(P ＞ 0.05).Conclusions Cephalomedullary nailing is effective for the treatment of femoral long oblique subtrochanteric fractures no matter it is assisted by minimally invasive cerclage or not.However,since minimally invasive cerclage has the advantage of improving reduction and mechanical stability,combination of minimally invasive cerclage and cephalomedullary nailing may be more advantageous in early pain-relieving and functional recovery.

Natural products are one of the most important sources for druggable lead compounds given their diverse structures and activities.Nevertheless,very few of them can be directly developed to drugs.The undesirable druggability of natural products result from their weaker activity,lower aqueous solubility and poorer stability.Since improving druggability by chemical modifications is restricted by the limited access to the complex structures of natural products,enzymatic modification has gradually become one of important tools for the structural modification of natural products.Meanwhile,since enzymatic glycosylation by glycosyltransferases has shown certain advantages such as excellent regio-and stereo-selectivity,high catalytic efficiency and mild conditions.It has been a promising route for the improvement of druggability for natural products.In the present review,we summarize different glycosyltransferases and their application for structural modification of natural products as well as the challenges issues involved in the glycosylation,which provides a general perspective on the enzymatic modification of natural products for the improvement of their draggability.

BACKGROUND:For the treatment of distal tibial fractures, open reduction and plate fixation, minimal y invasive percutaneous plate fixation and intramedul ary nail fixation are effective, but each has advantages and disadvantages. OBJECTIVE:To compare the effects of intramedul ary nail combined with blocking screws versus minimal y invasive percutaneous plate fixation in treating distal tibial fractures. METHODS:Fifty-one cases of distal tibial fractures were divided into two groups. The blocking screw group (23 cases) was treated with closed reduction and internal fixation with interlocking nail combined with blocking screws. The plate fixation group (28 cases) was treated with minimal y invasive percutaneous plate fixation. Fracture healing time, recovery of tibial function and complication occurrence were observed during fol ow-up. RESULTS AND CONCLUSION:Al patients were fol owed up for 8 to 32 months. (1) Except one patient in the plate fixation group, the other patients had bony union. The healing time was (4.6±1.7) months in the blocking screw group and (6.9±2.3) months in the plate fixation group. Significant differences in healing time were detected between the two groups (P<0.05). (2) The excel ent and good rate of tibial function recovery was significantly higher in the blocking screw group (100%) than in the plate fixation group (82%) (P<0.05). (3) No significant difference in the incidence of adverse events was determined between the blocking screw group (13%) and plate fixation group (18%) (P>0.05). (4) Results suggested that interlocking intramedul ary nail combined with blocking screw fixation in the treatment of distal tibial fractures can promote fracture healing and joint function recovery.