Multiple self-splicing introns in the 16S rRNA genes of giant sulfur bacteria

The gene encoding the small subunit rRNA serves as a prominent tool for the phylogenetic analysis and classification of Bacteria and Archaea owing to its high degree of conservation and its fundamental function in living organisms. Here we show that the 16S rRNA genes of not-yet-cultivated large sulfur bacteria, among them the largest known bacterium Thiomargarita namibiensis, regularly contain numerous self-splicing introns of variable length. The 16S rRNA genes can thus be enlarged to up to 3.5 kb. Remarkably, introns have never been identified in bacterial 16S rRNA genes before, although they are the most frequently sequenced genes today. This may be caused in part by a bias during the PCR amplification step that discriminates against longer homologs, as we show experimentally. Such length heterogeneity of 16S rRNA genes has so far never been considered when constructing 16S rRNA-based clone libraries, even though an elongation of rRNA genes due to intervening sequences has been reported previously. The detection of elongated 16S rRNA genes has profound implications for common methods in molecular ecology and may cause systematic biases in several techniques. In this study, catalyzed reporter deposition-fluorescence in situ hybridization on both ribosomes and rRNA precursor molecules as well as in vitro splicing experiments were performed and confirmed self-splicing of the introns. Accordingly, the introns do not inhibit the formation of functional ribosomes.     

应用变性梯度凝胶电泳分析牙周基础治疗前后龈下菌群的变化

目的:应用变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)方法观察比较牙周基础治疗前后龈下菌群微生态的总体变化,为临床诊疗方案的确定提供实验依据。方法:选取6例慢性牙周炎患者,观察牙周基础治疗前和治疗后6周时的临床指标变化,并采集治疗前后同一位点的龈下菌斑,提取总DNA,扩增不同的16S rDNA片段,DGGE分离,硝酸银染色,对图像进行聚类分析,并绘出聚类树形图。结果:所有患者经过治疗后,与基线相比,牙周状况均明显改善。基线和治疗后6周时,2个区间的DNA片段的条带数目无显著差异。通过聚类分析,证实同一患者基线时和基础治疗后6周时的龈下菌群具有较高的相似性,且不同的DNA片段所得到的条带图谱聚类树形图存在类似结果。结论:同一患者在基础治疗后形成的龈下菌群有类似于治疗前水平的趋势。DGGE能够观察龈下菌群的组成变化,适用于分析大量微生物标本的结构改变。     

Antibiotic effects on bacterial profile in osteonecrosis of the jaw

Oral Diseases (2011) 18 , 85–95 Objective: Oral infection is considered to play a critical role in the pathogenesis of bisphosphonate‐related osteonecrosis of the jaw (BRONJ), and antibiotic therapy has become a mainstay of BRONJ therapy. This study was aimed to investigate the effect of antibiotics on bacterial diversity in BRONJ tissues. Materials and methods: The bacterial profile from soft tissues associated with the BRONJ lesion was determined using 16S rRNA‐based denaturing gradient gel electrophoresis (DGGE) and sequencing. Twenty BRONJ subjects classified as stage 0–2 were enrolled in this study, and patient groups were divided into an antibiotic cohort (n = 10) treated with systemic antibiotic and a non‐antibiotic cohort (n = 10) with no prior antibiotic therapy. Results: The DGGE fingerprints indicated no significant differences in bacterial diversity of BRONJ tissue samples. Patients on antibiotics had higher relative abundance of phylum Firmicutes with bacterial species, Streptococcus intermedius, Lactobacillus gasseri, Mogibacterium timidum, and Solobacterium moorei, whereas patients without antibiotics had greater amounts of Parvimonas micra and Streptococcus anginosus. Thirty percent of bacterial populations were uncultured (yet‐to be cultured) phylotypes. Conclusion: This study using limited sample size indicated that oral antibiotic therapy may have a limited efficacy on the bacterial population associated with BRONJ lesions.     

Immune activation and increased IL‐21R expression are associated with the loss of memory B cells during HIV‐1 infection

Abstract. Ruffin N, Lantto R, Pensieroso S, Sammicheli S, Hejdeman B, Rethi B, Chiodi F (Karolinska Institutet, Stockholm; and South Hospital, Stockholm, Sweden). Immune activation and increased IL‐21R expression are associated with the loss of memory B cells during HIV‐1 infection. J Intern Med 2012; 272: 492–503. Objectives. Microbial translocation and chronic immune activation were previously shown to be associated with impairment of T cell functions and disease progression during infection with human immunodeficiency virus type‐1 (HIV‐1); however, their impact on B cell function and number remains unknown. By measuring markers of immune activation and molecules involved in apoptosis regulation, we have evaluated the association between microbial translocation and loss of memory B cells in HIV‐1‐infected patients. Methods. Markers of activation [the interleukin‐21 receptor (IL‐21R) and CD38] and apoptosis (Bim, Bcl‐2 and annexin V) were measured in B cell subpopulations by multicolour flow cytometry. Levels of soluble CD14 (sCD14) and lipopolysaccharide (LPS), measures of microbial translocation, were determined in plasma. Purified B cells were also exposed in vitro to Toll‐like receptor (TLR) ligands. Results. IL‐21R expression was higher in cells from HIV‐1‐infected patients, compared with control subjects, with the highest levels in nontreated patients. An inverse correlation was observed between IL‐21R expression and percentages of circulating resting memory (RM) B cells. IL‐21R‐positive memory B cells were also more susceptible to spontaneous apoptosis and displayed lower levels of Bcl‐2. It is interesting that the levels of sCD14, which are increased during HIV‐1 infection, were correlated with decreased percentages of RM B cells and high IL‐21R expression. In the plasma of HIV‐1‐infected individuals, a correlation was found between sCD14 and LPS levels. TLR activation of B cells in vitro resulted in IL‐21R up‐regulation. Conclusions. Microbial translocation and the associated immune activation during HIV‐1 infection may lead to high expression levels of the IL‐21R activation marker in RM B cells, a feature associated with increased apoptosis and a reduced number of these cells in the circulation.     

轻型胰腺炎患者早期给予软食的临床研究

目的探讨轻型胰腺炎患者早期摄入软食的效果,为该类患者的营养支持提供参考。方法将72例轻型胰腺炎患者随机分为观察组与对照组各36例。对照组允许经口进食后按常规开始给予流质食物,观察组拟定饮食处方,早期给予低脂高热量高蛋白软食,比较两组营养状况、消化道症状、继发感染及住院时间。结果干预2周后,观察组血清蛋白显著高于对照组,肠道菌群失调发生率显著低于对照组,住院时间显著短于对照组,感染发生率显著低于对照组(P0.05,P0.01)。结论轻型胰腺炎患者早期进软食能提供充足营养素及能量,纠正营养不良状况,减少肠源性感染的发生,促进患者疾病转归和预后。     

HIV immunotherapy comes of age: implications for prevention,treatment and cure

Antiretroviral therapy (ART) has reshaped the lives of millions of individuals infected with human immunodeficiency virus (HIV). Patients initiating ART early in the course of infection benefit from a considerable reduction in the risks of acquired immune deficiency syndrome (AIDS) and HIV-related inflammatory events. However, the absence of cure and lifelong requirements of treatment highlight the need of a vaccine and an immunotherapeutic strategy. Like for cancer, a paradigm shift has occurred with the contribution of immune activation and microbial translocation priming aberrant systemic immunity in restricting the ability of the host to mount an effective immune response. The approaches of implementing an effective vaccine to prevent infection and inhibition of immune activation with breakage of viral latency followed by vaccination should lead to an HIV-free generation.     

海兔素对乳腺肿瘤大鼠肠道屏障损伤的保护作用△

目的 探讨海兔素对二甲基苯蒽(7,12-dimethylbenz(a)anthracene, DMBA)诱发的乳腺肿瘤大鼠肠道屏障损伤的保护作用。方法30只雌性SD大鼠按体质量随机分为正常对照组(C)、模型组(M)和海兔素干预组(A)。模型组及海兔素干预组大鼠右侧臀部皮下一次性注射100 mg/kg DMBA建立乳腺癌模型。观察各组大鼠乳腺癌发生率及抑瘤率;酶联免疫吸附实验(ELISA)检测血浆中IL-4、IL-10、IL-6、TNF-α 浓度及D-乳酸(D-LA)和二胺氧化酶(DAO)的水平;实时荧光定量PCR技术(Real-Time PCR)对大鼠粪便肠道菌群16s RDNA V3可变区进行定量分析。结果 与模型组比较,海兔素组大鼠肿瘤潜伏期延长,肿瘤发生率和平均瘤质量降低(P均<0.05),抑瘤率达到49.83%,且该组胸腺指数明显升高(P<0.05);ELISA结果显示,与模型组比较,海兔素干预组IL-4浓度显著升高(P<0.05),IL-6的浓度显著降低 (P<0.05),D-LA的浓度显著降低(P<0.05);RT-PCR结果显示,海兔素干预后,大肠杆菌显著性降低(P<0.05),柔嫩梭菌及乳酸杆菌显著性升高 (P<0.05)。 结论 海兔素对大鼠乳腺肿瘤生长具有一定抑制作用,其作用机制可能与修复乳腺癌大鼠肠道屏障相关。