Estimation of 16S rRNA gene copy number in several probiotic Lactobacillus strains isolated from the gastrointestinal tract of chicken

The copy numbers of 16S rRNA genes in 12 probiotic Lactobacillus strains of poultry origin were analyzed. Genomic DNA of the strains was digested with restriction endonucleases that do not cut within the 16S rRNA gene of the strains. This was followed by Southern hybridization with a biotinylated probe complementary to the 16S rRNA gene. The copy number of the 16S rRNA gene within a Lactobacillus species was found to be conserved. From the hybridization results, Lactobacillus salivarius I 24 was estimated to have seven copies of the 16S rRNA gene, Lactobacillus panis C 17 to have five copies and Lactobacillus gallinarum strains I 16 and I 26 four copies. The 16S rRNA gene copy numbers of L. gallinarum and L. panis reported in the present study are the first record. Lactobacillus brevis strains I 12, I 23, I 25, I 211, I 218 and Lactobacillus reuteri strains C 1, C 10, C 16 were estimated to have at least four copies of the 16S rRNA gene. In addition, distinct rRNA restriction patterns which could discriminate the strains of L. reuteri and L. gallinarum were also detected. Information on 16S rRNA gene copy number is important for physiological, evolutionary and population studies of the bacteria.     

BldM对密旋链霉菌Act12形态发育及抗生素合成的调控

【目的】以多效生防菌株——密旋链霉菌(Streptomyces pactum) Act12为研究材料，探究转录因子BldM对生防链霉菌Act12形态发育及抗生素合成的调控作用。【方法】通过基因工程手段构建bldM基因缺失突变株△bldM及过表达突变株OE-bldM，利用扫描电镜观察、抑菌实验、高效液相色谱检测和实时荧光定量PCR探究缺失突变株△bldM及过表达突变株OE-bldM与野生型(wild) Act12在形态发育、生长速率、寡霉素产量及抗病原菌能力等方面的差异。【结果】经测序验证bldM基因缺失突变体△bldM及过表达突变体OE-bldM均构建成功，其中△bldM寡霉素D产量明显降低且无法形成气生菌丝，而过表达突变株OE-bldM的气生菌丝更加密集，产孢更为丰富。与野生型菌株相比，OE-bldM的寡霉素D产量增加了23%，编码寡霉素核心合成酶基因的转录水平上调了2-3倍，抑菌活性显著增强。【结论】全局性转录调控因子BldM不但能影响Act12气生菌丝及孢子形成，并且参与正调控Act12寡霉素的合成，本研究结果为转录因子BldM的调控功能进行了新的挖掘和补充，并为后续深入研究密旋...     

Enhancement of erythromycin A production with feeding available nitrogen sources in erythromycin biosynthesis phase

Effects of feeding different available nitrogen sources from 80 h in erythromycin biosynthesis phase on the erythromycin A (Er-A) production were investigated in 50 l fermenter. Feeding corn steep liquor and yeast extract, the Er-A production was enhanced, while the biotransformation from erythromycin C (Er-C) to Er-A had no increase. When ammonium sulphate was fed at high feeding rate, the maximal Er-A production and ratio of Er-A to Er-C were 7953 U/ml and 98.18:1 at 184 h, respectively, which were higher than that of the control (6742 U/ml and 5.47:1). The feeding ammonium sulphate process was successfully scaled up from 50 l to 25 m³ fermenter. The maximal Er-A production reached 7938 U/ml at 203 h, which was enhanced by 22.1% compared with the control (6501 U/ml at 192 h). The ratio of Er-A to Er-C was 24.05:1, which was higher than that of the control (4.77:1).     

WDR62 regulates spindle dynamics as an adaptor protein between TPX2/Aurora A and katanin

WDR62 is a microcephaly-related, microtubule (MT)-associated protein (MAP) that localizes to the spindle pole and regulates spindle organization, but the underlying mechanisms remain elusive. Here, we show that WDR62 regulates spindle dynamics by recruiting katanin to the spindle pole and further reveal a TPX2–Aurora A–WDR62–katanin axis in cells. By combining cellular and in vitro experiments, we demonstrate that WDR62 shows preference for curved segments of dynamic GDP-MTs, as well as GMPCPP- and paclitaxel-stabilized MTs, suggesting that it recognizes extended MT lattice. Consistent with this property, WDR62 alone is inefficient in recruiting katanin to GDP-MTs, while WDR62 complexed with TPX2/Aurora A can potently promote katanin-mediated severing of GDP-MTs in vitro. In addition, the MT-binding affinity of WDR62 is autoinhibited through JNK phosphorylation-induced intramolecular interaction. We propose that WDR62 is an atypical MAP and functions as an adaptor protein between its recruiting factor TPX2/Aurora A and the effector katanin to orchestrate the regulation of spindle dynamics.     

Antibacterial Δ1‐3‐Ketosteroids from the South China Sea Gorgonian Coral Subergorgia rubra

Three new Δ¹‐3‐ketosteroids characterized with a 9‐OH, subergosterones A–C ( 1 – 3 ), together with five known analogs 4 – 8 , were obtained from the gorgonian coral Subergorgia rubra collected from the South China Sea. The structures of 1 – 3 , including their absolute configurations, were determined by comprehensive spectroscopic methods and electronic circular dichroism (ECD) experiments. Compounds 2 and 3 exhibited inhibitory antibacterial activities against Bacillus cereus with MIC values of 1.56 μM .     

Similar or Totally Different: the Adjustment of the Twist Conformation Through Minor Structural Modification,and Dramatically Improved Performance for Dye‐Sensitized Solar Cell

A novel approach for enhancing the performance of dye‐sensitized solar cells is presented. It is based on the analysis of five sensitizers by utilizing triarylamine as donor, thiophene benzothiadiazole as chromophore and substituted thienyl linked with cyanoacrylic acid as the anchoring group (LI‐80‐LI‐84). Accompanied with the increasing steric hindrance of the substituents on the thienyl isolation group, the conformation of the dyes, in particular the angle between the chromophore and the anchoring group, becomes more and more twisted. Surprisingly, sensitizers with poorer conjugation effects (the higher twisted conformation) achieve better photovoltaic performances, showing a contrary trend to the traditional donor‐(π‐spacer)‐acceptor dyes with a better co‐planarity. On the basis of the preceding fundamental comprehensions, an empirical method is successfully applied to a new phenyl‐based system (LI‐85 and LI‐86) to improve their performances. The systematical investigation indicates that the twisted structures can contribute to the E_CB of the TiO₂ film, electron lifetime and resistance at the TiO₂/dye/electrolyte interface. Thereby, the efficiency of the initial LI‐80‐based cell has been dramatically improved to 2.45 times higher for LI‐86‐based cell, paving a new way for the design of better sensitizers with higher device performances.