一株柠檬内生细菌Z10的分离鉴定及其抑菌活性的发酵条件优化

【背景】 近年来,从植物内生菌的发酵产物中挖掘抑菌活性成分已成为寻找新型生物活性成分的重要途径。【目的】寻找新的具有高效抗菌活性的植物内生菌,并探究其产生抗菌活性物质的最优发酵条件和抑菌机制。【方法】 利用组织分离法和划线法从柠檬皮和籽核中分离内生菌株,按照滤纸片和牛津杯法筛选对病原菌具有较强抑制作用的菌株,通过形态观察和16S rRNA基因序列分析确定活性菌株的分类地位,基于微孔板法检测活性菌株发酵液提取液(B02c)的抑菌效果,以单因素试验和响应面试验设计对发酵条件进行优化,并通过碘化丙啶/SYTO-9探针标记结合流式细胞术检测B02c对检定菌细胞膜的影响。【结果】 从柠檬籽核中筛选出一株对金黄色葡萄球菌(Staphylococcus aureus)具有显著抑制作用的菌株Z10,鉴定为芽孢杆菌(Bacillus sp.);菌株Z10的最佳发酵条件为柑橘皮渣添加量1.6 g/100 mL、pH 6.8、接种量10.0%、转速172 r/min、培养时间36 h,优化后B02c的抑菌率达到84.36%,较优化前提升16.36%;B02c对金黄色葡萄球菌的最低抑制浓度(minimum inhibitory concentration, MIC)为3.125 mg/mL,其能够破坏金黄色葡萄球菌细胞膜的完整性。【结论】 柠檬内生菌Z10在优化发酵条件后获得的B02c对金黄色葡萄球菌具有良好的抑菌效果,在新型、高效的天然抑菌活性物质筛选及其工业化生产中具有一定应用前景。     

A new DNA methyltransferase M.BstC8I forms 5'-G(M5C)NNGC-3'. Studying of restriction endonuclease sensitivity to M.BstC8I-methylation

Bacillus stearothermophilus C8 was grown up on the Luria agar at 37 degrees C. A new DNA-methylase was determined in cellular lysate. The methylation of the DNAs of bacteriophages lambda and T7 in the region of 5'-G(m5C)NNGC-3' blocked the activity of BstC8I. Specificity of M.BstC8I was analyzed on methylated lambda DNA. For this purpose, we used computer modeling and the data on the sensitivity of restrictases BstC8I, BsuRI, AjnI, and PvuII to methylation. The sensitivity of some restrictases to new methylation was studied. The results may be used for DNA methylation studying.     

BtrI, a novel restriction endonuclease, recognises the non-palindromic sequence 5′-CACGTC(-3/-3)-3′

The recognition sequence and cleavage positions of a new restriction endonuclease BtrI isolated from Bacillus stearothermophilus SE-U62 have been determined. BtrI belongs to a rare type IIQ of restriction endonucleases, which recognise non-palindromic nucleotide sequences and cleave DNA symmetrically within them.     

Determination of substrate specificity of restriction endonuclease FauI

The recognition sequence and cleavage point of restriction endonuclease FauI have been determined as 5'-CCCGC(4/6). Not being isoschisomer of any known restriction endonuclease, this enzyme may be used in genetic engineering.     

POTENTIATION OF CAFFEINEINDUCED CONTRACTURE BY RAISING EXTRACELLULAR POTASSIUM IN FROG SKELETAL MUSCLE

用蛙胫前肌小束为材料,研究了提高胞外钾［Ｋ＋］Ｏ对咖啡因挛缩的作用。［Ｋ＋］Ｏ从２ｍｍｏｌ／Ｌ提高到１０或２５ｍｍｏｌ／Ｌ,由３ｍｍｏｌ／Ｌ咖啡因引起的挛缩明显增强。以ＰＫＣ／ＰＣ（ＰＫＣ和ＰＣ分别为在高钾和正常钾条件下的咖啡因挛缩）表示的咖啡因挛缩增强,依赖［Ｋ＋］Ｏ和高钾作用时间。随着１０ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用时间延长,直至１０ｍｉｎ,增强逐渐增加。但是,２５ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用１ｍｉｎ时增强达到最大,然后下降到对照。ＰＫＣ／ＰＣ变化时程不能用高钾引起的去极化解释,而与由相似［Ｋ＋］Ｏ引起的胞浆自由钙变化时程相符。提示,至少在蛙骨骼肌,高钾引起的咖啡因挛缩增强主要是由胞浆自由钙升高引起的。     

Type II SsrI restriction endonuclease from Staphylococcus saprophyticus

The recognition sequence and cleavage site for restriction endonuclease SsrI have been determined, the latter being 5'-GTT decreases AAC-3'. The enzyme was isolated from Staphylococcus saprophyticus strain and may be used in DNA investigation instead of its isoshizomer HpaI.     

Structural Composition of Myocardial Infarction Scar in Middle-aged Male and Female Rats: Does Sex Matter?

The present study was designed to determine whether the structural composition of the scar in middle-aged post–myocardial infraction (MI) rats is affected by the biological sex of the animals. A large MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. Four weeks after the MI, rats with transmural infarctions, greater than 50% of the left ventricular (LV) free wall, were evaluated. The extent of LV remodeling and fractional volumes of fibrillar collagen (FC), myofibroblasts, vascular smooth muscle (SM) cells, and surviving cardiac myocytes (CM) in the scars were compared between the two sexes. The left ventricle of post-MI male and female rats underwent a similar degree of remodeling as evidenced by the analogous scar thinning ratio (0.46 ± 0.02 vs. 0.42 ± 0.05) and infarct expansion index (1.06 ± 0.07 vs. 1.12 ± 0.08), respectively. Most important, the contents of major structural components of the scar revealed no evident difference between M-MI and F-MI rats (interstitial FC, 80.74 ± 2.08 vs. 82.57 ± 4.53; myofibroblasts, 9.59 ± 1.68 vs.9.56 ± 1.15; vascular SM cells, 2.27 ± 0.51 vs. 3.38 ± 0.47; and surviving CM, 3.26 ± 0.39 vs. 3.05 ± 0.38, respectively). Our data are the first to demonstrate that biological sex does not influence the structural composition of a mature scar in middle-aged post-MI rats.