Baicalin Represses Type Three Secretion System of Pseudomonas aeruginosa through PQS System

Therapeutics that target the virulence of pathogens rather than their viability offer a promising alternative for treating infectious diseases and circumventing antibiotic resistance. In this study, we searched for anti-virulence compounds against Pseudomonas aeruginosa from Chinese herbs and investigated baicalin from Scutellariae radix as such an active anti-virulence compound. The effect of baicalin on a range of important virulence factors in P. aeruginosa was assessed using luxCDABE-based reporters and by phenotypical assays. The molecular mechanism of the virulence inhibition by baicalin was investigated using genetic approaches. The impact of baicalin on P. aeruginosa pathogenicity was evaluated by both in vitro assays and in vivo animal models. The results show that baicalin diminished a plenty of important virulence factors in P. aeruginosa, including the Type III secretion system (T3SS). Baicalin treatment reduced the cellular toxicity of P. aeruginosa on the mammalian cells and attenuated in vivo pathogenicity in a Drosophila melanogaster infection model. In a rat pulmonary infection model, baicalin significantly reduced the severity of lung pathology and accelerated lung bacterial clearance. The PqsR of the Pseudomonas quinolone signal (PQS) system was found to be required for baicalin’s impact on T3SS. These findings indicate that baicalin is a promising therapeutic candidate for treating P. aeruginosa infections.     

平菇黄腐病病原菌分离与鉴定

本实验主要是对平菇黄腐病病原菌进行研究。从感染黄腐病的平菇幼菇子实体中分离得到2种具平板生长优势的革兰氏阴性杆状细菌(编号为G1和G2),通过对平菇子实体回接感染实验,发现细菌G1感染的平菇子实体病灶与自然感染的黄腐病状况一致,因此认为该菌就是导致平菇黄腐病的主要病原菌。经采用传统的生理生化实验与16s rDNA序列分析以及Biolog微生物自动鉴定系统分析鉴定,确定该菌为荧光假单胞菌(Pseudomonas fluorescens)。     

姜瘟病原菌的分离及其抑制物的筛选

从病姜上用梯度稀释法分离出病原菌 ,经鉴定为青枯假单胞菌 (P) (P .solanacearum) ,通过反复筛选 ,得到两种P的抑制物——— 2 ,4 ,4 三氯 2 羟基 联苯醚 (俗称三氯新 )和 2 ,4 ,4 三氯 5 溴 2 羟基 联苯醚 ,其最小抑菌浓度可达 1× 10 7g/ml。通过对其作用时间、杀灭浓度的研究和电镜结果 ,初步探明了该化合物能引起细菌染色质固缩 ,破坏细菌细胞壁 ,使细胞形态发生变化 ,最后崩解死亡。     

铜绿假单胞菌液体发酵产生絮凝现象的研究

对铜绿假单胞菌液体发酵产生的絮凝现象进行了研究。初步确定其由铜绿假单胞菌产生的生物膜引起,测得生物膜中多糖含量约为6.3%,蛋白质含量约为7.7%。考察了添加颗粒营养物质豆饼粉对絮凝现象的影响,分析了天然群体感应抑制剂水杨酸、丁香酚、儿茶素、姜黄素和大蒜提取物对生物膜和菌浓的影响以及群体感应淬灭酶对菌浓的影响。结果显示,添加颗粒营养物质对絮凝物影响不显著;天然群体感应抑制剂不能显著提高铜绿假单胞菌液体发酵菌浓,但对生物膜的分散具有一定作用;群体感应淬灭酶对铜绿假单胞菌液体发酵浓度无显著影响。     

Confirmation of the Biomethylation of Antimony Compounds

We have evidence that an organic and an inorganic salt of antimony were reduced and methylated biologically by microorganisms in laboratory experiments. The organoantimony compound produced was trimethylstibine [(CH₃)₃Sb] and was detected in a culture headspace. This was confirmed by matching the compound's retention time in capillary gas chromatography, as detected by fluorine-induced chemiluminescence, with a com- mercial standard and by its mass spectrum determined with gas chromatography/ mass spectrometry (GC–MS). (CH₃)₃Sb was detected in the headspace of soil samples amended with either potassium antimonyltartrate or potassium hexahydroxyantimonate and augmented with any one of three different nitrate-containing growth media. The identity of the microorganisms in soil that accomplished this are as yet unknown. Of 48 soil samples amended with these two compounds, 24 produced trimethylstibine. Bioreduction of trimethyldibromoantimony was also detected in a liquid monoculture of Pseudomonas fluorescens K27 which also produced tri- methylstibine. This headspace production of (CH₃)₃Sb was determined to be linked to the culture's cell population as measured by optical density. This microbe, however, did not biomethylate either potassium antimonyltartrate or potassium hexahydroxyantimonate in any experiments we performed. © 1997 John Wiley & Sons, Ltd.     

用全DNA转化法构建多功能石油降解菌

以嗜蜡的不动杆菌４－１ 作为受体菌,经溶菌酶破壁后,用嗜胶的假单胞菌Ｚ１７ 的全ＤＮＡ 转化,经再生后用只含高胶油的选择培养基筛选出转化子不动杆菌ＺＨ２０．破壁及再生的最佳条件为：溶菌酶浓度１．５ｍ ｇ／ｍ Ｌ,３７℃水浴保温４０ｍ ｉｎ,破壁率为９３．８％ ,再生率达到３０．２％ ;转化条件为：３０％ ＰＥＧ６０００,５０ｍ ｍ ｏｌ／ＬＣａＣｌ２ ,于３７℃保温２０ｍ ｉｎ．ＺＨ２０ 具有嗜高胶油和高蜡油的双重性状,５０℃条件下使高胶油粘度降低２２．２％ ,使高蜡油的凝固点降低２．５℃,且保持了受体菌的耐热和耐盐性能．液蜡培养基连续传代１０ 次,性能稳定．     

筛选假单胞菌株M18防治大棚黄瓜枯萎病害

设计了一种新的高效筛选程序,从植物根际土壤中分离出一株具有ＡＣＣ脱氨酶活性的促生拮抗双功能假单胞菌株Ｍ１８．在培养皿中,Ｍ１８能有效地抑制黄瓜枯萎病菌以及多种其他枯萎病原菌和植物病原菌的生长．Ｍ１８活菌浸种处理春黄瓜种子以及在大棚定植后根际土壤浇灌的试验中,与对照组相比,黄瓜枯萎病的株发病率降低７０％～８０％,霜霉病的发病率和病情指数都同时平均下降７０％左右,黄瓜产量提高２０％以上,每公顷可增加产值０．９万元以上,Ｍ１８的生物防治效果达到极显著程度．     

红罗非鱼"突眼病"病原的初步研究

从患“突眼病”的红罗非鱼眼球中分离出RT -E980 1菌 ,经人工感染试验确认为致病菌 .该菌大小为 (0 .6～ 1.0 ) μm× (1.3～ 2 .8) μm ,短杆状 ,单个、成对或链状 ,端生 3～ 4根鞭毛 ,革兰氏染色阴性 ,无芽孢 ,氧化葡萄糖产酸、不产气 ,氧化酶、过氧化氢酶试验阳性 ,MR、VP、H2 S反应阴性 ,能在SS、麦康凯培养基上生长 ,认为该菌系假单胞菌属(Pseudomonas)的种类 .药敏试验表明该菌对氟哌酸、环丙沙星、氟嗪酸、丁胺卡那霉素、庆大霉素、新霉素等敏感 .     

Berberine Derivatives as Pseudomonas aeruginosa MexXY-OprM Inhibitors: Activity and In Silico Insights

The natural alkaloid berberine has been demonstrated to inhibit the Pseudomonas aeruginosa multidrug efflux system MexXY-OprM, which is responsible for tobramycin extrusion by binding the inner membrane transporter MexY. To find a structure with improved inhibitory activity, we compared by molecular dynamics investigations the binding affinity of berberine and three aromatic substituents towards the three polymorphic sequences of MexY found in P. aeruginosa (PAO1, PA7, and PA14). The synergy of the combinations of berberine or berberine derivatives/tobramycin against the same strains was then evaluated by checkerboard and time-kill assays. The in silico analysis evidenced different binding modes depending on both the structure of the berberine derivative and the specific MexY polymorphism. In vitro assays showed an evident MIC reduction (32-fold and 16-fold, respectively) and a 2–3 log greater killing effect after 2 h of exposure to the combinations of 13-(2-methylbenzyl)- and 13-(4-methylbenzyl)-berberine with tobramycin against the tobramycin-resistant strain PA7, a milder synergy (a 4-fold MIC reduction) against PAO1 and PA14, and no synergy against the ΔmexXY strain K1525, confirming the MexY-specific binding and the computational results. These berberine derivatives could thus be considered new hit compounds to select more effective berberine substitutions and their common path of interaction with MexY as the starting point for the rational design of novel MexXY-OprM inhibitors.     

Process Engineering for Production of Chiral Hydroxycarboxylic Acids from Bacterial Polyhydroxyalkanoates

An efficient process for the production of (R)‐hydroxycarboxylic acids (RHAs) from polyhydroxyalkanoates (PHAs) was developed. It involved the synthesis of PHA in bacteria, followed by bringing the culture broth directly to a pH optimal for in vivo PHA degradation, thus avoiding cell collection by centrifugation and pellet resuspension. The optimal pH was maintained to allow maximal release of RHAs. Using this process, cells having a dry weight (w) of 1.8 g · L⁻¹ and 45% (w/w) PHA exhibited a linear PHA degradation rate of about 0.059 g · L⁻¹ · h⁻¹ in the first 9 h. Concomitantly, RHAs were released with a rate of 0.057 g · L⁻¹ · h⁻¹. Further incubation of up to 15 h resulted in almost 90% (w/w) degradation of PHA. Based on this approach in combination with chemostat and a plug flow reactor a continuous process for the production of RHAs could be achieved.