极地放线菌次级代谢产物及药理活性研究进展CSCD

极地微生物处在南北极严峻、极端的自然环境下,体内的一些“沉默基因”可能会被激活,形成了独特的生存机制和生物合成途径,能够产生化学结构多样、活性显著的次级代谢产物。近年来,从极地放线菌中分离鉴定出一系列结构新颖、活性突出的次级代谢产物。本文综述了1999至2021年间的极地放线菌次级代谢产物及药理活性的研究进展,将极地放线菌来源的104个次级代谢产物按肽类、生物碱类、萜类、大环内酯类、聚酮类、大环内酰胺类等化学类别,着重介绍结构新颖和活性突出的次级代谢产物,为进一步开发利用极地放线菌、研发创新药物提供参考。     

深海来源真菌次级代谢产物研究进展

深海环境复杂多样,微生物为了适应这种极端环境往往会形成独特的代谢途径,进而产生一些具有某种生理活性的结构新颖的次级代谢产物。真菌作为深海环境中的重要微生物类群之一,因其次级代谢产物出新率高、生物活性显著,近年来成为海洋天然产物研究的焦点,倍受研究者关注。本文综述了2004-2017年间发表的217个深海(50 m)真菌来源的新颖次级代谢产物,其来源菌株广泛分布在真菌18个属,主要集中在Penicillium属(30%)、Aspergillus属(24%)、Spiromastix属(13%)和Acremonium属(7%);其结构类型包括聚酮类(99个)、生物碱类(54个)、萜类(50个)、肽类(11个)、其他类(3个);活性研究主要集中在细胞毒性、抗菌、抗病毒、抗污损等方面。     

微生物共培养在新活性化合物挖掘中的研究进展

微生物次级代谢产物结构新颖、活性多样,一直以来都是药物及其先导化合物的重要来源。但近年来在普通微生物纯培养中发现的新活性物质不断减少,重复发现逐渐增加;而微生物共培养因更加接近微生物生长的自然环境,在药物及其先导物挖掘方面发挥着越来越重要的作用。本文分析了近5年来利用真菌vs真菌、真菌vs细菌共培养挖掘新活性化合物的研究现状,以及研究中存在的问题。     

链霉菌来源生物碱及药理活性研究进展

不同来源的链霉菌所产生的次级代谢产物具有结构新颖、复杂多样且生物活性良好,是具有研究潜力的药物资源;生物碱类化合物是链霉菌代谢产物中重要活性成分之一。近十年从链霉菌中已经报道了许多生物碱的成分,本文按菌株来源综述了2007~2017年间报道的链霉菌来源的生物碱及其生物活性,为其他研究生物碱及其活性研究提供指导。     

海洋动物来源微生物的共培养研究进展

近年来,由于一些新疾病的发生和细菌耐药性的出现,微生物来源次级代谢产物的筛选重复率越来越高,微生物一些代谢基因在现有实验室条件下无法表达,所以需要发现新的微生物资源,同时找到激活微生物代谢产物基因的方法。海洋动物体内蕴含着大量的共附生微生物资源,可以产生很多具有生物活性的化合物,是潜在的药用资源。本文综述了近年来海洋动物(海鞘、海绵、珊瑚和海葵等)来源的微生物进行共培养的研究策略,包括共培养菌株的选择、共培养条件、群体感应和信号分子对共培养菌株的影响,以及不同种类微生物间的共培养实例。共培养与单培养相比,增加了次级代谢产物的种类,提高了次级代谢产物的生物活性或产量。共培养的研究有助于发现新的海洋动物来源微生物的活性天然产物,为海洋药物的开发提供新思路。     

微生物来源天然产物中的β-甲基色氨酸单元及其生物合成研究进展

微生物在次级代谢过程中通常会产生结构复杂、活性多样的天然产物。这些天然产物是新药发展的基础,亦可作为先导化合物或重要的药效基团用于药物研发。结构多样的氨基酸单元是参与合成复杂多样天然产物的重要前体。天然产物中的β-甲基氨基酸单元不仅可以赋予其生物活性,还能增强其生物稳定性而不被肽酶水解。本文综述了含有β-甲基氨基酸单元的天然产物,尤其对含有β-甲基色氨酸单元的天然产物生物合成途径进行了阐释。对β-甲基色氨酸单元生物合成途径的理解结合基因组数据有助于进行新结构天然产物的挖掘,并为运用代谢科学理念和合成生物学技术开发含有该单元的新化合物提供理论基础和可操作遗传元件。     

低温型真菌抗肿瘤活性次级代谢产物研究进展

真菌栖息生境及物种的多样性使其次级代谢产物化学结构和生物活性呈多样性特点,结构与功能多样的真菌次级代谢产物已成为新药先导化合物发现的重要资源。低温型真菌因其独特而恶劣的生存环境进化出特有的适冷特性及代谢途径,使其产生结构新颖、活性显著的次级代谢产物的几率大大提升,已成为药物研发的热点领域。近年来,研究者陆续从高海拔地区、南北极地和深海地带等低温生境分离鉴定出上百种结构新颖的次级代谢产物,并显示出抗肿瘤、抗菌、抗病毒和免疫调节等多种活性。本文对近10年来源于上述生境的低温型真菌抗肿瘤活性次级代谢产物的研究进展进行综述,为其用于创制抗肿瘤新药提供新思路。     

微生物来源天然产物中的β-甲基色氨酸单元及其生物合成研究进展

微生物在次级代谢过程中通常会产生结构复杂、活性多样的天然产物。这些天然产物是新药发展的基础,亦可作为先导化合物或重要的药效基团用于药物研发。结构多样的氨基酸单元是参与合成复杂多样天然产物的重要前体。天然产物中的β-甲基氨基酸单元不仅可以赋予其生物活性,还能增强其生物稳定性而不被肽酶水解。本文综述了含有β-甲基氨基酸单元的天然产物,尤其对含有β-甲基色氨酸单元的天然产物生物合成途径进行了阐释。对β-甲基色氨酸单元生物合成途径的理解结合基因组数据有助于进行新结构天然产物的挖掘,并为运用代谢科学理念和合成生物学技术开发含有该单元的新化合物提供理论基础和可操作遗传元件。     

真菌诱导子在发酵工业中的应用现状及展望

真菌诱导子是一类能诱导植物和微生物产生次级代谢产物的活性物质,它一经识别,将通过信号转导途径,引起相关基因表达发生变化,从而调节次级代谢产物合成途径中相关酶的活性,诱导特定次级代谢产物的积累。近年来国内外在真菌诱导子诱导途径及机制方面进行了深入研究,同时在生物工业领域,尤其在发酵工业中的应用也引起了广泛关注。以下结合本实验室的研究工作,重点介绍了真菌诱导子在植物和微生物细胞次级代谢产物合成方面的应用现状、诱导机制和存在的问题及展望。     

影响变形链球菌生物膜形成因素的研究进展

龋病的发生发展过程中,致龋微生物生物膜(biofilm)形成是龋病发生的首要因素。变形链球菌(Streptococcus mutans)等在口腔生物膜内进行产酸代谢活动是产生龋病的直接原因。因此,控制S.mutans生物膜的形成可以减少龋病的发生、发展。本文就影响变形链球菌生物膜形成的因素研究进展做一综述。     

一株产右旋糖苷酶海洋细菌的筛选鉴定

【目的】筛选鉴定产右旋糖苷酶的海洋细菌,并对其所产右旋糖苷酶的酶学性质及在变异链球菌牙菌斑生物膜中的应用进行初步研究。【方法】利用平板透明圈法从海洋环境中筛选产右旋糖苷酶的细菌,根据菌株形态特征、生理特征及16S rDNA序列确定其分类学地位,采用体外生物膜模型研究该酶对变异链球菌牙菌斑生物膜形成的抑制作用。【结果】从海泥中筛选出一株产右旋糖苷酶的细菌KQ11,初步鉴定为节杆菌(Arthrobacter sp.)。该菌株的最适生长温度为30°C,最适生长pH 7.5,最适生长NaCl浓度为0.4%。右旋糖苷酶的最适作用温度为45°C,最适作用pH为5.5。该酶能有效地抑制变异链球菌牙菌斑生物膜的形成。【结论】菌株KQ11右旋糖苷酶能够抑制变异链球菌牙菌斑生物膜的形成,可望用于漱口液等口腔护理产品中。     

The anti-biofouling effect of Lactobacillus fermentum-derived biosurfactant against Streptococcus mutans

Biofouling in the oral cavity often causes serious problems. The ability of Streptococcus mutans to synthesize extracellular glucans from sucrose using glucosyltransferases (gtfs) is vital for the initiation and progression of dental caries. Recently, it was demonstrated that some biological compounds, such as secondary metabolites of probiotic bacteria, have an anti-biofouling effect. In this study, S. mutans was investigated for the anti-biofouling effect of Lactobacillus fermentum (L.f.)-derived biosurfactant. It was hypothesized that two enzymes produced by S. mutans, glucosyltransferases B and C, would be inhibited by the L.f.-biosurfactant. When these two enzymes were inhibited, fewer biofilms (or none) were formed. RNA was extracted from a 48-h biofilm of S. mutans formed in the presence or absence of L.f. biosurfactant, and the gene expression level of gtfB/C was quantified using the real-time polymerase chain reaction (RT-PCR). L.f. biosurfactant showed substantial anti-biofouling activity because it reduced the process of attachment and biofilm production and also showed a reduction in gtfB/C gene expression (P value?相似文献   

Both lactoferrin and iron influence aggregation and biofilm formation in Streptococcus mutans

Streptococcus mutans, a gram-positive immobile bacterium, is an oral pathogen considered to be the principal etiologic agent of dental caries. Although some researches suggest that trace metals, including iron, can be associated with dental caries, the function of salivary iron and lactoferrin in the human oral cavity remains unclear. The data reported in this study indicates that iron-deprived saliva (Fe3+ < 0.1 microM) increases S. mutans aggregation and biofilm formation in the fluid and adherent phases as compared with saliva (Fe3+ from 0.1 to 1 microM), while iron-loaded saliva (Fe3+ > 1 microM) inhibits both phenomena. Our findings are consistent with the hypothesis that S. mutans aggregation and biofilm formation are negatively iron-modulated as confirmed by the different effect of bovine lactoferrin (bLf), added to saliva at physiological concentration (20 microg/ml) in the apo- or iron-saturated form. Even if saliva itself induces bacterial aggregation, iron binding capability of apo-bLf is responsible for the noticeable increase of bacterial aggregation and biofilm development in the fluid and adherent phases. On the contrary, iron-saturated bLf decreases aggregation and biofilm development by supplying iron to S. mutans. Therefore, the iron-withholding capability of apo-Lf or native Lf is an important signal to which S. mutans counteracts by leaving the planktonic state and entering into a new lifestyle, biofilm, to colonize and persist in the human oral cavity. In addition, another function of bLf, unrelated to its iron binding capability, is responsible for the inhibition of the adhesion of S. mutans free, aggregated or biofilm on abiotic surfaces. Both these activities of lactoferrin, related and unrelated to the iron binding capability, could have a key role in protecting the human oral cavity from S. mutans pathogenicity.     

The role of fructans on dental biofilm formation by Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus

Dental plaque biofilm plays a pivotal role in the progression of dental diseases. Polysaccharides are of great importance in the ecology of the dental biofilm. We studied the effect of fructans, glucans and a mixture of both fructans and glucans, synthesized in situ by immobilized fructosyltransferase or glucosyltransferase, on the adhesion of Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus to hydroxyapatite beads coated with human saliva (sHA). The adhesion of A. viscosus to sHA was found to be fructan-dependent. Adhesion of both S. sobrinus and S. mutans was found to be mediated mainly by glucans, while the adhesion of S. gordonii was found to be both glucan- and fructan-dependent. Treatment with fructanase prior to A. viscosus adhesion resulted in a significant reduction in adhesion to sHA, while adhesion of S. sobrinus, S. mutans and S. gordonii was slightly influenced by fructanase treatment. Treatment with fructanase after adhesion of S. gordonii to sHA resulted in a significant reduction in their adhesion to sHA. Our results show that fructans may play a role in the adhesion and colonization of several cariogenic bacteria to sHA, thus contributing to the formation of dental plaque biofilm.     

Roles of salivary components in Streptococcus mutans colonization in a new animal model using NOD/SCID.e2f1-/- mice

Streptococcus mutans plays an important role in biofilm formation on the tooth surface and is the primary causative agent of dental caries. The binding of S. mutans to the salivary pellicle is of considerable etiologic significance and is important in biofilm development. Recently, we produced NOD/SCID.e2f1(-/-) mice that show hyposalivation, lower salivary antibody, and an extended life span compared to the parent strain: NOD.e2f1(-/-). In this study we used NOD/SCID.e2f1(-/-) 4 or 6 mice to determine the roles of several salivary components in S. mutans colonization in vivo. S. mutans colonization in NOD/SCID.e2f1(-/-) mice was significantly increased when mice were pre-treated with human saliva or commercial salivary components. Interestingly, pre-treatment with secretory IgA (sIgA) at physiological concentrations promoted significant colonization of S. mutans compared with sIgA at higher concentrations, or with human saliva or other components. Our data suggest the principal effects of specific sIgA on S. mutans occur during S. mutans colonization, where the appropriate concentration of specific sIgA may serve as an anti-microbial agent, agglutinin, or an adherence receptor to surface antigens. Further, specific sIgA supported biofilm formation when the mice were supplied 1% sucrose water and a non-sucrose diet. The data suggests that there are multiple effects exerted by sIgA in S. mutans colonization, with synergistic effects evident under the condition of sIgA and limited nutrients on colonization in NOD/SCID.e2f1(-/-) mice. This is a new animal model that can be used to assess prevention methods for dental biofilm-dependent diseases such as dental caries.     

Reduction of saliva-promoted adhesion of Streptococcus mutans MT8148 and dental biofilm development by tragacanth gum and yeast-derived phosphomannan

The aim of this study was to investigate materials which reduce saliva-promoted adhesion of Streptococcus mutans onto enamel surfaces, and their potential in preventing dental biofilm development. The effects of hydroxyapatite (HA) surface pretreatment with hydrophilic polysaccharides on saliva-promoted S. mutans adhesion in vitro and de novo dental biofilm deposition in vivo were examined. Saliva-promoted adhesion of S. mutans MT8148 was significantly reduced by pretreatment of the HA surface with tragacanth gum (TG) and yeast-derived phosphoglycans. Extracellular phosphomannan (PM) from Pichia capsulata NRRL Y-1842 and TG reduced biofilm development on lower incisors in plaque-susceptible rats when administered via drinking water at concentrations of 0.5% and 0.01%, respectively. The inhibitory effect of TG on de novo dental biofilm formation was also demonstrated when administered via mouthwash in humans. It is concluded that TG and yeast-derived PM have the potential for use as anti-adherent agents and are effective in reducing de novo dental biofilm formation.     

Cell Density Modulates Acid Adaptation in Streptococcus mutans: Implications for Survival in Biofilms

Streptococcus mutans normally colonizes dental biofilms and is regularly exposed to continual cycles of acidic pH during ingestion of fermentable dietary carbohydrates. The ability of S. mutans to survive at low pH is an important virulence factor in the pathogenesis of dental caries. Despite a few studies of the acid adaptation mechanism of this organism, little work has focused on the acid tolerance of S. mutans growing in high-cell-density biofilms. It is unknown whether biofilm growth mode or high cell density affects acid adaptation by S. mutans. This study was initiated to examine the acid tolerance response (ATR) of S. mutans biofilm cells and to determine the effect of cell density on the induction of acid adaptation. S. mutans BM71 cells were first grown in broth cultures to examine acid adaptation associated with growth phase, cell density, carbon starvation, and induction by culture filtrates. The cells were also grown in a chemostat-based biofilm fermentor for biofilm formation. Adaptation of biofilm cells to low pH was established in the chemostat by the acid generated from excess glucose metabolism, followed by a pH 3.5 acid shock for 3 h. Both biofilm and planktonic cells were removed to assay percentages of survival. The results showed that S. mutans BM71 exhibited a log-phase ATR induced by low pH and a stationary-phase acid resistance induced by carbon starvation. Cell density was found to modulate acid adaptation in S. mutans log-phase cells, since pre-adapted cells at a higher cell density or from a dense biofilm displayed significantly higher resistance to the killing pH than the cells at a lower cell density. The log-phase ATR could also be induced by a neutralized culture filtrate collected from a low-pH culture, suggesting that the culture filtrate contained an extracellular induction component(s) involved in acid adaptation in S. mutans. Heat or proteinase treatment abolished the induction by the culture filtrate. The results also showed that mutants defective in the comC, -D, or -E genes, which encode a quorum sensing system essential for cell density-dependent induction of genetic competence, had a diminished log-phase ATR. Addition of synthetic competence stimulating peptide (CSP) to the comC mutant restored the ATR. This study demonstrated that cell density and biofilm growth mode modulated acid adaptation in S. mutans, suggesting that optimal development of acid adaptation in this organism involves both low pH induction and cell-cell communication.     

Multiple Streptococcus mutans Genes Are Involved in Biofilm Formation

Streptococcus mutans has been strongly implicated as the principal etiological agent in dental caries. One of the important virulence properties of these organisms is their ability to form biofilms known as dental plaque on tooth surfaces. Since the roles of sucrose and glucosyltransferases in S. mutans biofilm formation have been well documented, we focused our attention on sucrose-independent factors. We have initially identified several mutants that appear to be defective in biofilm formation on abiotic surfaces by an insertional inactivation mutagenesis strategy applied to S. mutans. A total of 27 biofilm-defective mutants were isolated and analyzed in this study. From these mutants, three genes were identified. One of the mutants was defective in the Bacillus subtilis lytR homologue. Another of the biofilm-defective mutants isolated was a yulF homologue, which encodes a hypothetical protein of B. subtilis whose function in biofilm formation is unknown. The vast majority of the mutants were defective in the comB gene required for competence. We therefore have constructed and examined comACDE null mutants. These mutants were also found to be attenuated in biofilm formation. Biofilm formation by several other regulatory gene mutants were also characterized using an in vitro biofilm-forming assay. These results suggest that competence genes as well as the sgp and dgk genes may play important roles in S. mutans biofilm formation.     

A proteomic approach for exploring biofilm in Streptococcus mutans

Biofilm formation by Streptococcus mutans is considered as its principal virulence factor, causing dental caries. Mutants of S. mutans defective in biofilm formation were generated and analyzed to study the collective role of proteins in its formation. Mutants were characterized on the basis of adherence to saliva-coated surface, and biofilm formation. The confocal laser microscopy and scanning electron microscopy images showed that the control biofilms had cluster of cells covered by layer of exo-polysaccharide while the biofilms of mutants were thin and spaced. Two-dimensional protein electrophoresis data analysis identified 57 proteins that are either up (44 proteins) or down (13 proteins) regulated. These data points to the importance of up and down regulated proteins in the formation of biofilm in Streptococcus mutans.     

Streptococcus mutans and oral streptococci in dental plaque

The human oral microbial biota represents a highly diverse biofilm. Twenty-five species of oral streptococci inhabit the human oral cavity and represent about 20 % of the total oral bacteria. Taxonomy of these bacteria is complex and remains provisional. Oral streptococci encompass friends and foes bacteria. Each species has developed specific properties for colonizing the different oral sites subjected to constantly changing conditions, for competing against competitors, and for resisting external agressions (host immune system, physico-chemical shocks, and mechanical frictions). Imbalance in the indigenous microbial biota generates oral diseases, and under proper conditions, commensal streptococci can switch to opportunistic pathogens that initiate disease in and damage to the host. The group of "mutans streptococci" was described as the most important bacteria related to the formation of dental caries. Streptococcus mutans, although naturally present among the human oral microbiota, is the microbial species most strongly associated with carious lesions. This minireview describes the oral streptococci ecology and their biofilm life style by focusing on the mutans group, mainly S. mutans. Virulence traits, interactions in the biofilm, and influence of S. mutans in dental caries etiology are discussed.