Cloning and Characterization of a Thermostable Endolysin of Bacteriophage TP-84 as a Potential Disinfectant and Biofilm-Removing Biological Agent

The obligatory step in the life cycle of a lytic bacteriophage is the release of its progeny particles from infected bacterial cells. The main barrier to overcome is the cell wall, composed of crosslinked peptidoglycan, which counteracts the pressure prevailing in the cytoplasm and protects the cell against osmotic lysis and mechanical damage. Bacteriophages have developed two strategies leading to the release of progeny particles: the inhibition of peptidoglycan synthesis and enzymatic cleavage by a bacteriophage-coded endolysin. In this study, we cloned and investigated the TP84_28 endolysin of the bacteriophage TP-84, which infects thermophilic Geobacillus stearothermophilus, determined the enzymatic characteristics, and initially evaluated the endolysin application as a non-invasive agent for disinfecting surfaces, including those exposed to high temperatures. Both the native and recombinant TP84_28 endolysins, obtained through the Escherichia coli T7-lac expression system, are highly thermostable and retain trace activity after incubation at 100 °C for 30 min. The proteins exhibit strong bacterial wall digestion activity up to 77.6 °C, decreasing to marginal activity at ambient temperatures. We assayed the lysis of various types of bacteria using TP84_28 endolysins: Gram-positive, Gram-negative, encapsulated, and pathogenic. Significant lytic activity was observed on the thermophilic and mesophilic Gram-positive bacteria and, to a lesser extent, on the thermophilic and mesophilic Gram-negative bacteria. The thermostable TP84_28 endolysin seems to be a promising mild agent for disinfecting surfaces exposed to high temperatures.     

罗801块微生物驱油菌种代谢产物分析

为了研究罗801块微生物驱油菌种代谢产物,从代谢产物化学性质的角度探索驱油作用机理,依据微生物代谢规律,应用气相色谱、气质联用仪(气相色谱-质谱GC-MS)、傅立叶变换红外光谱仪等化学分析仪器和手段,建立了一套通用的驱油菌种代谢产物定性定量分析方法:短链脂肪酸和生物气气相色谱分析,长链脂肪酸、醇类、酚类以及生物烃的预处理和GC-MS分析,醛类、酮类的衍生化及GC-MS分析,生物表面活性物质的薄层层析和红外光谱定性分析,脂类化合物的GC-MS定量分析等;介绍了罗801块驱油菌种代谢产物分析结果:罗801块驱油菌种代谢产物共检出近百种化合物,不同菌种代谢产物种类和数量差异较大。驱油菌种代谢产物分析说明了驱油菌种代谢的复杂性,该研究对矿场试验效果评价及微生物驱油机理探索有重要意义。     

Bottom-Up法计算油田注入水中三种细菌的不确定度

为保持地下压力,在油田开采过程中需向地下油层中注水,注入水中最为常见的三种细菌是腐生菌、铁细菌和硫酸还原菌,这些细菌的存在会降低注入水水质并腐蚀管道,影响油田开采。为客观评价三种细菌检测的准确度,采用绝迹稀释法检测技术,利用Bottom-Up法,通过21组数据对三种细菌检测方法的不确定度进行计算。结果表明,绝迹稀释法检测油田注水三种细菌的不确定度分别为:硫酸还原菌±4 mL^-1,腐生菌±6 mL^-1,铁细菌±16 mL^-1。通过Bottom-Up法对检测不确定度进行评估,可真实、准确地反应油田注入水中三种细菌的实际含量范围,为油田注水达标提供技术保障。     

Atomic-Resolution Structures and Mode of Action of Clinically Relevant Antimicrobial Peptides

Global rise of infections and deaths caused by drug-resistant bacterial pathogens are among the unmet medical needs. In an age of drying pipeline of novel antibiotics to treat bacterial infections, antimicrobial peptides (AMPs) are proven to be valid therapeutics modalities. Direct in vivo applications of many AMPs could be challenging; however, works are demonstrating encouraging results for some of them. In this review article, we discussed 3-D structures of potent AMPs e.g., polymyxin, thanatin, MSI, protegrin, OMPTA in complex with bacterial targets and their mode of actions. Studies on human peptide LL37 and de novo-designed peptides are also discussed. We have focused on AMPs which are effective against drug-resistant Gram-negative bacteria. Since treatment options for the infections caused by super bugs of Gram-negative bacteria are now extremely limited. We also summarize some of the pertinent challenges in the field of clinical trials of AMPs.     

膳食纤维抗肿瘤作用研究

该文在对近年国内外有关膳食纤维研究文献的研究基础上,总结膳食纤维在抗肿瘤方面机理及对食品中致癌物代谢影响。     

黄铁矿烧渣微生物脱硫

在烧渣生物脱硫的试验.论研究了矿浆浓度、Fe³⁺浓度及pH值对游离T.f菌浓度和脱硫率的影响.证明烧渣脱硫是T.f.菌直接浸出作用和由细菌而产生的Fe³⁺间接浸出作用的联合;脱硫速率和菌种氧化活性受到吸附在固相上和液相中细菌生长情况、矿浆浓度、pH值和Fe³⁺的影响;三价铁离子的添加可影响菌种活性,抑制浸出的进行,且易在矿物表面产生沉淀,降低氧化率.烧渣生物脱硫后,可达到铁精矿标准.     

Whole soybean as probiotic lactic acid bacteria carrier food in solid-state fermentation

For the purpose of preparing lactic acid bacteria (LAB) carrier food, the solid-state fermentation of whole soybean was performed using Bifidobacterium animalis 937, Lactobacillus casei Zhang and Lactobacillus plantarum P-8 mixed with Bacillus subtilis natto, respectively. The physicochemical properties, the amino nitrogen content and peptide molecular weight distribution of the fermented whole soybean products were examined during this process. After 48 h of fermentation, the viable counts of the three samples were 1.41 × 10⁸ CFU/g (B. animalis 937), 1.74 × 10¹⁰ CFU/g (L. casei Zhang) and 2.19 × 10¹⁰ CFU/g (L. plantarum P-8), with the pH declined rapidly from 6.32 to 5.78, 5.60 and 5.44 at the early stage of the fermentation and increased to 6.71, 6.47 and 6.60 at the later stage of the fermentation. The fermentation caused a sharply increase in the content of the free amino nitrogen from 99.7 μmol/g to 301.9 μmol/g, 390.1 μmol/g and 529.1 μmol/g in the solid fermented soybean products, due to the multiplication of microorganism and the effect of enzyme system. Furthermore, the levels of soybean peptide with molecular weight less than 1000 Da increased 30.7%, 71.2% and 81.3% relative to that of the control group at 48 h. The result of the present work implied that whole soybean fermented by LAB can provide the different probiotics for the host, and there is potential to develope nutritious fermented soybean products.     

Cereal‐based fermented foods in developing countries: ancient foods for modern research

Cereal‐based fermented foods are major contributors to energy intake in developing countries (DC). Their microbiota is dominated by lactic acid bacteria and has been extensively investigated. Diversity studies have been facilitated by molecular methods enabling genotyping of isolates; the rapid development of ‘omics’ approaches should facilitate more comprehensive studies to describe the relation between microbial diversity, cell physiology and product characteristics. Also, the link between the food microbiota and health benefits, in particular in nutrition, should be investigated. There is a need to encourage researches in the field of DC cereal‐based foods in direction of more mechanistic approaches.     

Characterization and Technological Properties of Lactic Acid Bacteria Isolated from Traditional Argentinean Goat’s Milk Products

A total of 286 lactic acid bacteria isolated from goat’s dairy products in northwest of Argentina were characterized. Lactobacilli (38%) and cocci (62%) were identified according to morphological, physiological, and relevant technological properties. L. plantarum (14%) and Enterococcus (34%) were the predominant species. S. thermophilus, Pediococcus and L. plantarum were the highest acid producers. Eight strains of L. fermentum produced bacteriocins or metabolites similar to bacteriocins. The API-ZYM test was applied to 39 isolates. Eight strains were selected from their both technological properties and enzymatic activities for use as starter or adjunct culture in the manufacture of artisanal goat cheeses.     

A survey on bacteria isolated as hydrogen sulfide-producers from marine fish

Aim of the work was to identify sulfide-producers isolated from tuna and swordfish and to evaluate some physiological characteristics, particularly those that could be related to spoiling potential.16S rDNA sequencing revealed Shewanella baltica as the main species, followed by Serratia spp. and other Shewanella species, while RAPD- and rep-PCR analyses indicated the presence of several biotypes. Shewanella baltica and Shewanella putrefaciens showed rapid growth at 4 and 8 °C, production of TMA and H₂S, amino acids decarboxylation and proteolytic activity also at refrigeration temperatures, therefore being potentially able to modify texture and sensory characteristics of finfish. Extracellular DNAse activity and growth in presence of high salt concentrations can provide a competitive advantage in unfavourable environments.Our data provide new insights into specific metabolic features of Shewanella spp., rarely studied before, such as extracellular DNAse activity and amino acid decarboxylating activity. Moreover, our results highlight the clear necessity of more specific media and research methods to count H₂S-producing bacteria.