Epidemiological application of a new bacteriocin typing scheme for Streptococcus mutans

We propose a new bacteriocin typing scheme for Streptococcus mutans (Biotype I) using nine producer strains and a numerical code with three figures. Its application in 75 unrelated S. mutans strains allowed us to type all microorganisms and to obtain a total of 15 bacteriocin types. Its epidemiological use in two family groups allowed us to obtain two bacteriocin types in each one and to show the type relations between the different family components.     

New targets in the search for preventive and therapeutic agents for botulism

Botulism is a severe neuroparalytic disease resulting from exposure to one of the most poisonous toxins to humans. Because of this high potency and the use of toxins as biological weapons, botulism is a public health concern and each case represents an emergency. Current therapy involves respiratory supportive care and anti-toxins administration. As a preventive measure, vaccination against toxins represents an effective strategy but is undesirable due the rarity of botulism and the effectiveness of toxins in treating several neuromuscular disorders. This paper summarizes the current issues in botulism treatment and prevention, highlighting the challenge for future researches.     

Interactions between and within Streptococcus mutans and Streptococcus sobrinus isolated from humans harboring both species

Abstract— The prevalence of Streptococcus mutans and Streptococcus sobrinus was examined in plaque samples from small discrete areas of the buccal tooth surfaces of seven subjects. Strains of S. mutans and S. sobrinus were isolated and tested for bacteriocin-mediated interactions between and within the two species, using the stab inoculation technique. S. mutans and S. sobrinus did not colonize each tooth surface uniformly and, in plaque from small discrete sites, S. mutans and S. sobrinus were either undetected or present in different interspecies proportions. Within the same subject, there were no bacteriocin-mediated interactions between strains of the same mutans species and no difference in bacteriocin activity was found between the strains of S. mutans and S. sobrinus from different sites. When bacteriocin interactions were tested between isolated strains from all seven subjects a somewhat higher inhibition ability was found for producer strains isolated from plaque compared with those isolated from saliva. S. mutans appeared to be more bacteriocinogenic than S. sobrinus . Replacing the glucose in the medium with sucrose enhanced the bacteriocin activity of S. mutans towards other S. mutans strains but reduced the inhibitory interaction towards strains of S. sobrinus .     

唾液链球菌在口臭治疗中的研究进展

口臭主要是指由口腔内厌氧菌发酵产生的挥发性硫化物引起的口腔异味。传统的机械治疗方法和化学治疗方法虽然可以短期内改善口臭状况,但长期疗效不尽如人意。唾液链球菌属于口腔正常菌群,与健康者相比,口臭者口腔中唾液链球菌数量较少。研究表明,唾液链球菌可以产生某种细菌素,对口臭相关细菌有抑制作用。本文综述了唾液链球菌在口臭预防和治疗中的研究进展。     

海洋源细菌素研究现状及展望

细菌素是细菌通过核糖体合成的抗菌肽,通常能抑制分类地位相近的其他细菌的生长。自20世纪20年代以来报道的陆地源细菌素已多达数千例。乳酸链球菌素是研究得最为透彻的陆地源细菌素,且被公认为安全有效的天然食品生物保鲜剂,在欧美的食品工业中具有广泛应用。与陆地源数以千计的细菌素相比,海洋环境中已发现的细菌素尚不足百种。但有些已发现的海洋源细菌素却表现出陆地源细菌素所不具备的独特活性以及较大的应用潜力,如一些海洋源细菌素具有的对革兰氏阴性耐药性菌的拮抗活性,显示出其成为一线抗革兰氏阴性药物多黏菌素替代品的潜在可能。海洋细菌素的研究正受到越来越多的关注。本文从产生菌、样品来源、结构特性等方面对2009年以来报道的海洋细菌素进行了回顾,对海洋细菌素的研究现状及新细菌素的发现手段进行了分析及讨论。展望未来海洋源细菌素的研究,相信随着深海采样技术、海洋细菌培养技术及细菌素研究技术的进步,越来越多的海洋细菌素产生菌将会进入研究视野,更多结构新颖、活性良好的海洋细菌素也将会被发现。     

血链球菌细菌素对牙龈卟啉单胞菌生长曲线及细胞内钙离子浓度的影响

目的：研究血链球菌细菌素对牙龈卟啉单胞菌（Porphyromonas gingivalis P．g）生长曲线的影响。探讨血链球菌细菌素对牙龈卟啉单胞菌细胞内钙离子浓度的影响。方法：通过低温高速离心，超声破碎等方法提取血链素，使血链素作用P．g，于37℃厌氧培养：采用微量液体对倍稀释法测定血链素对P．g的最小抑菌浓度（MIC）。选用不同浓度的血链素作用P．g，分别于0、4、8、12、16、20、24、48h时测定各组细菌悬液在590nm波长处的A值，并绘制生长曲线。用Fluo-3／AM负载P．g细胞内钙离子，在激光共聚焦显微镜下观察Ca抖荧光强度变化。结果：血链素对P．g有显著抑制作用，其MIC为0．0625g／L。血链素作用后，P．g的生长曲线在8～16h发生显著改变，对数生长期被延迟了8h。血链素作用后，P．g细胞内钙离子浓度显著降低，与对照组相比差异具有统计学意义（P〈0．01）。结论：血链球菌细菌素对牙龈卟啉单胞菌有明显的抑制作用，在本实验范围内，随着血链素浓度的升高其抑制作用逐渐增强。血链球菌细菌素可导致牙龈卟啉单胞菌细胞膜钙离子通透性增强。     

Lactobacillus plantarum bacteriocin is associated with intestinal and systemic improvements in diet-induced obese mice and maintains epithelial barrier integrity in vitro

We investigated the Lactobacillus plantarum bacteriocin plantaricin EF (PlnEF) system for its contributions to L. plantarum mediated benefits in a mouse model of diet-induced obesity. C57BL/6J mice on a high-fat diet (HFD) were administered a rifampicin resistant mutant of L. plantarum NCMIB8826 (NICMB8826-R) or an isogenic ΔplnEFI mutant strain, LM0419, every 48 h for nine weeks. Mice fed wild-type L. plantarum, but not LM0419, reduced their consumption of the HFD starting three weeks into the study and exhibited an overall 10% reduction in weight gain. The responses were independent of glucose homeostasis, as both NCMIB8826-R and LM0419 fed mice had improved oral glucose tolerance compared to sham controls. Although bacteriocins have antibacterial properties, the ileal, cecal, and fecal microbiota and cecocolic metabolomes were unchanged between mice fed either wild-type L. plantarum or the ΔplnEFI mutant. Instead, only mice fed NCMIB8826-R showed an increased production of ZO-1 in ileal tissues. To verify a potential role for the plantaricin EF system in supporting intestinal epithelial function, synthesized PlnEF peptides were applied to Caco-2 cell monolayers challenged with TNF-α and IFN-γ. The combination of PlnE and PlnF were required to prevent sustained cytokine-induced losses to Caco-2 cell para- and transcellular permeability and elevated IL-8 levels. In conclusion, this study shows that probiotic L. plantarum ameliorates the effects of obesogenic diets through a mechanism that involves the plantaricin EF system and likely includes L. plantarum – induced fortification of the intestinal epithelium.     

Novel antimicrobial peptide discovery using machine learning and biophysical selection of minimal bacteriocin domains

Bacteriocins, the ribosomally produced antimicrobial peptides of bacteria, represent an untapped source of promising antibiotic alternatives. However, bacteriocins display diverse mechanisms of action, a narrow spectrum of activity, and inherent challenges in natural product isolation making in vitro verification of putative bacteriocins difficult. A subset of bacteriocins exert their antimicrobial effects through favorable biophysical interactions with the bacterial membrane mediated by the charge, hydrophobicity, and conformation of the peptide. We have developed a pipeline for bacteriocin-derived compound design and testing that combines sequence-free prediction of bacteriocins using machine learning and a simple biophysical trait filter to generate 20 amino acid peptides that can be synthesized and evaluated for activity. We generated 28,895 total 20-mer candidate peptides and scored them for charge, α-helicity, and hydrophobic moment. Of those, we selected 16 sequences for synthesis and evaluated their antimicrobial, cytotoxicity, and hemolytic activities. Peptides with the overall highest scores for our biophysical parameters exhibited significant antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa. Our combined method incorporates machine learning and biophysical-based minimal region determination to create an original approach to swiftly discover bacteriocin candidates amenable to rapid synthesis and evaluation for therapeutic use.     

Dental caries is a preventable infectious disease

Dental caries is the most common infectious disease affecting humans. The principal causative agents are a group of streptococcal species collectively referred to as the mutans streptococci of which Streptococcus mutans and Streptococcus sobrinus are the most important agents of human caries. This review outlines what is currently known about these ubiquitous pathogens and discusses novel methods for elimination of these bacteria from dental plaque.