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。     

Nano and Microtechnologies for the Study of Magnetotactic Bacteria

Magnetotactic bacteria (MTB) naturally synthesize magnetic nanoparticles that are wrapped in lipid membranes. These membrane‐bound particles, which are known as magnetosomes, are characterized by their narrow size distribution, high colloidal stability, and homogenous magnetic properties. These characteristics of magnetosomes confer them with significant value as materials for biomedical and industrial applications. MTB are also a model system to study key biological questions relating to formation of bacterial organelles, metal homeostasis, biomineralization, and magnetoaerotaxis. The similar size scale of nano and microfluidic systems to MTB and ease of coupling to local magnetic fields make them especially useful to study and analyze MTB. In this Review, a summary of nano‐ and microtechnologies that are developed for purposes such as MTB sorting, genetic engineering, and motility assays is provided. The use of existing platforms that can be adapted for large‐scale MTB processing including microfluidic bioreactors is also described. As this is a relatively new field, future synergistic research directions coupling MTB, and nano‐ and microfluidics are also suggested. It is hoped that this Review could start to bridge scientific communities and jump‐start new ideas in MTB research that can be made possible with nano‐ and microfluidic technologies.     

Heme-dependent and heme-independent nitrite reduction by lactic acid bacteria results in different N-containing products

Seventy strains of lactic acid bacteria were investigated for nitrite reductase activity. Two types of this activity were detected. Type I was found in Lactobacillus plantarum, L. pentosus and Pediococcus pentosaceus. This activity is heme-dependent with ammonia as the sole product. Type II mechanism is heme-independent and reduces nitrite to NO and N₂O.     

Bacteria-Responsive Multidrug Delivery Nanosystem for Combating Long-Term Biofilm-Associated Infections

Microbial biofilm formation on implantable devices causes chronic infections that cannot be treated with existing antimicrobials. Quorum sensing inhibitors (QSIs) have recently emerged as novel antimicrobials for the prevention of biofilm formation. But blocking QS alone is insufficient to inhibit biofilm-associated chronic infections. Herein, chitosan hollow nanospheres are capped by bacteria-responsive β-casein to form a synergistic antifouling nanosystem consisting of a QSI and bactericide. β-casein is degraded by protease in a bacteria-colonized microenvironment in situ thus, QSI and bactericide are released sequentially. The release of QSI sensitises bacteria effectively through reduction of surface hydrophobicity, eDNA content, and lipopolysaccharide production in biofilms, amplifying the chemotherapeutic action of the bactericide. Compared to the uncoated surface, the coated surface inhibits biofilm formation and removes preformed biofilms of Pseudomonas aeruginosa PAO1 and methicillin-resistant Staphylococcus aureus by 1.8 logs and 1.9 logs of biomass inhibition, respectively. The coated catheters are found to stay clean for 30 days under artificial urine flow, while the uncoated catheters are clogged by bacterial biofilms within 5 days. Finally, the long term antifouling activity in vivo is confirmed. Overall, the nanosystem is devoted to making urinary catheters resistant to bacterial biofilm formation for the long term.     

威远页岩气区块某平台配液用水与采出水细菌群落演替规律

目的探究在页岩气生产过程中的关键腐蚀细菌,解析其中细菌潜在的演替规律。方法利用16S rRNA高通量测序分析技术对威远地区页岩气某平台配液用水和采出水菌群进行检测。结果清水配液的细菌结构与采出水、回用返排液完全不同,压裂后细菌的丰富度及多样性降低;关键腐蚀细菌包括弓形杆菌属(Arcobacter)、海细菌属(Marinobacterium)、假单胞菌属(Pseudomonas)等;清水配液中细菌群落是由嗜温、好氧、硫酸盐还原和产酸等功能较弱的细菌为主,而回用返排液中存在大量具有硫代谢、产酸和产生物膜功能的细菌,经压裂后,采出水中以兼性厌氧、厌氧或严格厌氧,即具有硫酸盐还原、硫还原、硫氧化、产酸、产生物膜、铁还原等功能的细菌为主,并鉴定出部分嗜热细菌。结论可为进一步研究集输管道细菌腐蚀及管道防护提供理论与技术支持。     

渤海湾盆地陈家庄油田陈22块微生物异常分布研究

为探索油气藏上方微生物异常分布,按照从线到面的研究思路,采集渤海湾盆地陈家庄油田陈22块油气藏上方土壤样品469个,采用MPN法检测出样品中油气指示微生物的数量并研究其分布特征。结果显示,在联井剖面上,甲烷氧化菌和烃氧化菌2种油气指示微生物异常区与对应油井位置有很高的吻合度,呈顶端异常,剖面南北两端具有明显的背景区,表明了2种油气指示微生物对油气藏烃类微渗漏的指示性是有效的。进一步对本区块油气微生物进行了面上精查,结合地质和钻井信息,解析了微生物异常与下覆油气藏分布的响应关系,结果表明地表土壤中油气微生物对下覆油气藏的分布有很好的指示作用,同时对钻井部署也有一定的参考价值。     

Growth inhibition of Listeria monocytogenes by bacteriocin-producing Staphylococcus equorum SE3 in cheese models

The anti-listerial activity of Staphylococcus equorum SE3 isolated from cheese brine was tested in two different model cheese systems to ascertain its potential for use as a protective culture for smear cheese ripening. Co-cultivation of Listeria monocytogenes L129 and the antilisterial S. equorum SE3 was performed on “milk agar” or “modified milk agar” (model cheese surface systems). S. equorum inoculated at concentrations of 10⁶ cfu/cm² completely inhibited growth of L. monocytogenes inoculated at 10–500 cfu/cm² on modified milk agar within 24 h of incubation, in the negative controls L129 grew to >10⁷ cfu/cm². At a higher inoculation level, growth inhibition was still more than 7 log units after 24 h. L. monocytogenes strains of different serotypes were also inhibited. Co-cultivation of S. equorum SE3 with other smear bacteria or yeasts, however, showed no growth inhibition of these important ripening microorganisms. The antilisterial effect was not diminished on the modified milk agar when co-cultivation was performed with the added smear cheese microbiota. However, on milk agar with no adjuncts (“green cheese model”), only a slight (<1 log unit) growth inhibition of L. monocytogenes was observed. Addition of peptides or amino acids to milk agar could restore growth inhibition of listeriae at different levels.     

Combined treatment with chlorine dioxide gas,fumaric acid,and ultraviolet-C light for inactivating Escherichia coli O157:H7 and Listeria monocytogenes inoculated on plums

Combined non-thermal treatment with chlorine dioxide (ClO₂) gas, ultraviolet-C (UV-C) light, and fumaric acid was performed to inactivate Listeria monocytogenes and Escherichia coli O157:H7 inoculated on plums. Plums were treated with ClO₂ gas (15 and 30 ppmv), fumaric acid (0.1, 0.3, and 0.5%), and by UV-C irradiation (3, 5, and 10 kJ/m²). The single treatments with 15 or 30 ppmv ClO₂ gas, 0.5% fumaric acid, and 10 kJ/m² UV-C decreased the population of L. monocytogenes by 1.78, 2.00, 1.65, and 1.62 log CFU/g, respectively, and the population of E. coli O157:H7 by 1.73, 1.81, 1.34, and 2.07 log CFU/g, respectively. In addition, combined treatments reduced the populations of the pathogenic bacteria more than each treatment alone. In particular, the combined treatment with ClO₂ gas (30 ppmv) for 20 min, fumaric acid (0.5%), and UV-C (10 kJ/m²) decreased the populations of L. monocytogenes and E. coli O157:H7 by 6.26 and 5.48 log CFU/g, respectively. These results suggest that combined treatment with ClO₂ gas, UV-C light, and fumaric acid may be a useful hurdle technology to enhance the microbiological safety of plums.     

Consumption patterns,bacteriological quality and risk factors for Salmonella contamination in meat-based meals consumed outside the home in Kigali,Rwanda

Meat-based meals are consumed as a source of animal proteins and constitute one of the leading vehicles for food borne infections in humans. The main objective of this study was to determine the consumption pattern and the bacteriological quality of meat-based meals consumed outside households in Kigali. A survey on meat consumption patterns was carried out in 400 households by using a questionnaire, whereas different meat-based meals were sampled from 150 snack bars and restaurants. Enumeration of hygiene indicator bacteria (total mesophilic bacteria and Escherichia coli) and the qualitative detection of Salmonella were carried out by using conventional culture methods. The results indicated that goat was the type of meat that was consumed the most outside the home in Kigali and the meat intake varied significantly (p ≤ 0.05) with the social category of the household. The average levels of total aerobic bacteria and E. coli in meat-based meals were found to be 4.7 and 1.4 log cfu/g, respectively, whereas Salmonella was detected in 11.7% of all meat-based meals. Eight factors mostly linked to the cooking treatments and hygienic handling practices for cooked meals were found to be significantly (p ≤ 0.05) associated with the risk of Salmonella occurrence in meat-based meals consumed outside the home in Kigali. The findings from this study strongly suggest the need for proper cooking and/or improvements in hygiene in the establishments selling ready-to-eat meat-based meals in Kigali, particularly those located in rural localities.     

Antibacterial activity of cranberry juice concentrate on freshness and sensory quality of ready to eat (RTE) foods

Ready-to-eat (RTE) foods are not further treated before consumption in such a way that may significantly reduce the microbial load, therefore the risk of foodborne disease must be considered. In this regard, the use of natural antimicrobial compounds is an interesting method to be considered. On this topic, the antibacterial activity of cranberry juice concentrate (CJC) have been evaluated in vitro and in situ against 3 foodborne pathogenic bacteria. Results showed a high antimicrobial effect with a noticeable inhibition capacity against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium. Acid sensitivity studies of bacteria indicated that at the same pH level (pH = 2.4) in presence of organic acid solution (citric and quinic acids), cranberry juice concentrate showed greater antibacterial effects than the acids due to their phenolic compounds. In situ studies showed 2.5, 1.8 and 5 log reduction of E. coli, L. monocytogenes and S. typhimurium, respectively in presence of cranberry juice concentrate, on pre-cut red peppers after 7 days of storage at 4 °C. A total inhibition of L. monocytogenes on fresh cranberry fruits in primary day of storage, was observed. Cranberries treated with CJC also showed a 3 log reduction of S. typhimurium after 4 days of storage at 4 °C. The results suggest that CJC can be an effective preservation, source of natural antibacterial, to protect the RTE foods from foodborne pathogens contamination without effecting on sensorial properties of treated samples and allow to maintain the freshness, sensory and the nutritional quality of RTE foods.