Coagulase-negative staphylococci species affect biofilm formation of other coagulase-negative and coagulase-positive staphylococci

Coagulase-negative staphylococci (CNS) are considered to be commensal bacteria in humans and animals, but are now also recognized as etiological agents in several infections, including bovine mastitis. Biofilm formation appears to be an important factor in CNS pathogenicity. Furthermore, some researchers have proposed that CNS colonization of the intramammary environment has a protective effect against other pathogens. The mechanisms behind the protective effect of CNS have yet to be characterized. The aim of this study was to evaluate the effect of CNS isolates with a weak-biofilm phenotype on the biofilm formation of other staphylococcal isolates. We selected 10 CNS with a weak-biofilm phenotype and 30 staphylococcal isolates with a strong-biofilm phenotype for this study. We measured biofilm production by individual isolates using a standard polystyrene microtiter plate assay and compared the findings with biofilm produced in mixed cultures. We confirmed the results using confocal microscopy and a microfluidic system with low shear force. Four of the CNS isolates with a weak-biofilm phenotype (Staphylococcus chromogenes C and E and Staphylococcus simulans F and H) significantly reduced biofilm formation in approximately 80% of the staphylococcal species tested, including coagulase-positive Staphylococcus aureus. The 4 Staph. chromogenes and Staph. simulans isolates were also able to disperse pre-established biofilms, but to a lesser extent. We also performed a deferred antagonism assay and recorded the number of colony-forming units in the mixed-biofilm assays on differential or selective agar plates. Overall, CNS with a weak-biofilm phenotype did not inhibit the growth of isolates with a strong-biofilm phenotype. These results suggest that some CNS isolates can negatively affect the ability of other staphylococcal isolates and species to form biofilms via a mechanism that does not involve growth inhibition.     

4种防腐剂对副溶血弧菌生物膜形成的抑制作用

在确定4种防腐剂壳聚糖、山梨酸钾、脱氢乙酸钠和ε-聚赖氨酸对副溶血弧菌(Vibro parahaemolyticus)的最小抑菌浓度(minimum inhibitory concentration,MIC)的基础上,研究其对副溶血弧菌生物膜的抑制作用。采用结晶紫染色法测生物膜形成量,XTT法测生物膜代谢活性,硫酸-苯酚法测定生物膜中胞外多糖的分泌量。结果表明,壳聚糖的MIC最小,为1.25 mg/m L。4种防腐剂在MIC以及亚抑菌浓度条件下对副溶血弧菌生物膜均有明显的抑制作用,不仅抑制生物膜的形成,而且能显著降低细菌的代谢活性,减少胞外多糖的分泌,其中壳聚糖对副溶血弧菌生物膜的抑制作用最强。     

基于高通量测序的郫县豆瓣后发酵期细菌多样性研究

为研究郫县豆瓣后发酵过程中细菌变化规律,揭示其特有"日晒夜露"工艺的发酵本质,采用MiSeq测序分析其从后发酵1周至后发酵6 a期间一共8个时间点的细菌群落演替变化情况。结果表明,郫县豆瓣后发酵过程中共有57个门类群、174个纲类群、321个目类群、535个科类群、921个属类群的细菌参与演替变化。后发酵时间对郫县豆瓣的细菌群落组成具有重要影响,随着后发酵的进行肠杆菌科和链形菌科持续减少,而鞘脂单胞菌科、芽孢杆菌科、梭菌科和消化链球菌科的细菌则出现先增加后减少,其峰值大多出现在1~3 a,但后发酵6 a的郫县豆瓣细菌群落较其他样品呈明显偏低。该方法发现了大量的非培养细菌和未报道细菌,所得细菌多样信息更接近于样品微生态,更能够全面解析自然发酵调味品—郫县豆瓣的细菌多样性,为传统产业的现代化改造和食品质量安全控制提供了科学支撑。     

用于农残快速检测的离心式微流控芯片研制

基于酶抑制原理结合光度分析方法,研制一种预存储生化试剂的离心式微流控芯片。设计制作的一次性微流控CD芯片集成进样、酶抑制反应、显色反应及检测单元,结合自行研制的便携式分析装置,可以同时检测12个样品,能够实现对大批量农产品中有机磷和氨基甲酸酯类农药残留进行现场、快速、高通量检测。结果表明:与传统农残快速测定仪比较,微流控芯片农残速测系统操作单元集成度高,可以实现农残检测流程的自动化,样品及试剂消耗量降至传统速测方法的约1/20,同时检测灵敏度、重复性和准确性整体优于传统农残快速测定仪,可以满足基层非专业人员针对大批量样品农药残留的筛查需求。     

Next‐Generation Sequencing Analyses of Bacterial Community Structures in Soybean Pastes Produced in Northeast China

Fermented soybean foods contain nutritional components including easily digestible peptides, cholesterol‐free oils, minerals, and vitamins. Various fermented soybean foods have been developed and are consumed as flavoring condiments in Asian regions. While the quality of fermented soybean foods is largely affected by microorganisms that participate in the fermentation process, our knowledge about the microorganisms in soybean pastes manufactured in Northeast China is limited. The current study used a culture‐independent barcoded pyrosequencing method targeting hypervariable V1/V2 regions of the 16S rRNA gene to evaluate Korean doenjang and soybean pastes prepared by the Hun Chinese (SPHC) and Korean minority (SPKM) populations in Northeast China. In total, 63399 high‐quality sequences were derived from 16 soybean paste samples collected in Northeast China. Each bacterial species‐level taxon of SPHC, SPKM, and Korean doenjang was clustered separately. Each paste contained representative bacterial species that could be distinguished from each other: Bacillus subtilis in SPKM, Tetragenococcus halophilus in SPHC, and Enterococcus durans in Korean doenjang. This is the 1st massive sequencing‐based study analyzing microbial communities in soybean pastes manufactured in Northeast China, compared to Korean doenjang. Our results clearly showed that each soybean paste contained unique microbial communities that varied depending on the manufacturing process and location.     

Molecular Cloning and Characterizations of Xylanase Inhibitor Protein from Wheat (Triticum Aestivum)

Xylanase inhibitor proteins (XIPs) were regarded to inhibit the activity of xylanases during baking and gluten‐starch separation processes. To avoid the inhibition to xylanases, it is necessary to define the conditions under which the inhibition takes place. In this study, we cloned the XIP gene from 2 different variety of Triticum aestivum, that is, Zhengmai 9023 and Zhengmai 366, and investigated the properties of XIP protein expressed by Pichia pastoris. The results showed that the 2 XIP genes (xip‐9023 and xip‐366) were highly homologous with only 3 nucleotide differences. XIP‐9023 showed the optimal inhibition pH and temperature were 7 °C and 40 °C, respectively. Inhibition of xylanase by XIP‐9023 reached the maximum in 40 min. At 50% inhibition of xylanase, the molar ratio of inhibitor: xylanase was 26:1. XIP‐9023 was active to various fungal xylanases tested as well as to a bacterial xylanase produced by Paenibacillus sp. isolated from cow rumen.     

Effect of raspberry pomace extracts isolated by high pressure extraction on the quality and shelf‐life of beef burgers

Raspberry pomace extracts isolated with supercritical carbon dioxide (SCE) and pressurised ethanol/water (ETE) were tested in beef burgers. Only ETE additives effectively inhibited lipid oxidation and the growth of microorganisms, as it was observed by measuring the changes of thiobarbituric acid reactive substances, bacterial counts and the content of O₂ and CO₂ during storage in the modified atmosphere package. ETE additives also demonstrated some meat colour preservation effects, which were assessed by the intensity of hamburger colour and metmyoglobin concentration. However, ETE additives did not alter burger's taste at the applied concentrations (up to 1%). It may be concluded that the most effective extracts possessing strong antioxidant and antimicrobial activity may be isolated from raspberry pomace by the pressurised liquid extraction with a hydroethanolic solvent; such extracts may be considered as promising additives in meat products for improving their stability and enriching with beneficial to health phytochemicals.     

Effects of bacterial direct-fed microbials on ruminal characteristics,methane emission,and milk fatty acid composition in cows fed high- or low-starch diets

This study investigated the effects of bacterial direct-fed microbials (DFM) on ruminal fermentation and microbial characteristics, methane (CH₄) emission, diet digestibility, and milk fatty acid (FA) composition in dairy cows fed diets formulated to induce different ruminal volatile fatty acid (VFA) profiles. Eight ruminally cannulated dairy cows were divided into 2 groups based on parity, days in milk, milk production, and body weight. Cows in each group were fed either a high-starch (38%, HS) or a low-starch (2%, LS) diet in a 55:45 forage-to-concentrate ratio on a dry matter (DM) basis. For each diet, cows were randomly assigned to 1 of 4 treatments in a Latin square design of (1) control (CON); (2) Propionibacterium P63 (P63); (3) P63 plus Lactobacillus plantarum 115 (P63+Lp); (4) P63 plus Lactobacillus rhamnosus 32 (P63+Lr). Strains of DFM were administered at 10¹⁰ cfu/d. Methane emission (using the sulfur hexafluoride tracer technique), total-tract digestibility, dry matter intake, and milk production and composition were quantified in wk 3. Ruminal fermentation and microbial characteristics were measured in wk 4. Data were analyzed using the mixed procedure of SAS (SAS Institute Inc., Cary, NC). The 2 diets induced different ruminal VFA profiles, with a greater proportion of propionate at the expense of acetate and butyrate for the HS diet. Greater concentrations of total bacteria and selected bacterial species of methanogenic Archaea were reported for the HS diet, whereas the protozoa concentration in HS decreased. For both diets, bacterial DFM supplementation raised ruminal pH (+0.18 pH units, on average) compared with CON. Irrespective of diet, P63+Lp and P63+Lr increased ruminal cellulase activity (3.8-fold, on average) compared with CON, but this effect was not associated with variations in ruminal microbial numbers. Irrespective of diet, no effect of bacterial DFM on ruminal VFA was observed. For the LS diet, supplementing cows with P63+Lr tended to decrease CH₄ emission (26.5%, on average, when expressed per kilogram of milk or 4% fat-corrected milk). Only P63 supplementation to cows fed the HS diet affected the concentration of some milk FA, such as cis isomers of 18:1 and intermediates of ruminal biohydrogenation of polyunsaturated FA. Overall, bacterial DFM could be useful to stabilize ruminal pH. Their effects on CH₄ production mitigation and milk FA profile depended on DFM strain and diet and should be confirmed under a greater variation of dietary conditions.     

Illumina高通量测序技术分析中周羌稞养生酒窖泥细菌多样性

以不同窖龄（5年、10年、20年和30年）的中周羌稞养生酒窖泥为研究对象,利用Illumina高通量测序技术对窖泥细菌16S rRNA V4～V5区进行测序,分析其细菌多样性。结果表明,窖泥中细菌多样性（Shannon指数）和丰富度（Chao指数）随着窖龄的增加而显著提高（P＜0.05）。不同窖龄窖泥的细菌群落组成存在差异,盐扁菌科（Haloplasmataceae）、乳酸杆菌科（Lactobacillaceae）,瘤胃球菌属（Ruminococcaceae）和梭菌属（Clostridium）为不同窖龄窖泥的共有细菌;类芽孢杆菌属（Paemibacillus）、芽孢杆菌属（Bacillus）、消化球菌科（Peptococcaceae）、喜盐芽孢杆菌属（Haloballus）和链球菌属（Streptococcus）只出现在30年窖龄窖泥中;PCA结果分析表明,相同窖龄窖泥中的细菌具有更高的相似性,说明窖龄是影响窖泥细菌群落组成的重要因素之一。     

浙江地区中温大曲贮存过程细菌群落多样性及功能预测分析

利用16S rRNA高通量测序和理化分析技术分别解析浙江地区中温大曲贮存过程中细菌群落多样性和理化特征演替,并结合生物信息学方法预测菌群功能。结果表明,大曲贮存90 d后,pH和含水量显著降低（P<0.05）,酸度显著升高（P<0.05）,且贮存前后细菌群落多样性和结构组成差异显著（P<0.05）。乳酸杆菌属（Lactobacillus）和魏斯式菌属（Weissella）是大曲贮存期间的绝对优势属,其相对丰度范围分别为47.56%～63.44%和25.16%～42.77%。魏斯式菌属相对丰度与含水量和pH呈正相关,而酸度与乳酸杆菌属、醋酸杆菌属（Acetobacter）和克罗彭斯特菌属（Kroppenstedtia）相对丰度呈正相关。此外,功能预测结果表明中温大曲贮存期间的基因功能主要与代谢、遗传信息处理和环境信息处理等功能相关。