Isolation and identification of low-density polyethylene (LDPE) biodegrading bacteria from waste landfill in Yazd

Microorganisms used as a biodegradation technique can provide economic benefits and can be compatible with the environment. The aim of this study was to isolate low-density polyethylene (LDPE) degrading bacteria. The waste samples were collected from Yazd landfills. Biochemical and molecular tests based on 16S rDNA sequencing were done to identify the superior isolates. Biodegradation rate was measured using weight loss measurement, spectroscopic analysis with Fourier-transform infrared (FTIR) spectroscopy and an investigation of surface morphology changes using scanning electron microscopy (SEM). Two biodegrading isolates were identified as Pseudomonas aeruginosa strain SKN1 and strain SKN2. The weight loss of LDPE strips was measured at 10.32%. SEM micrographs showed the surface degradation and colony formation on LDPE strips. The FTIR spectrum revealed the structural changes on LDPE strip surfaces. Bio-decomposition was observed to have taken place and the bacterial strains had a special ability to biodegrade LDPE wastes.     

Phenol degradation by isolated bacterial strains: kinetics study and application in coking wastewater treatment

BACKGROUND: In biological treatment of coking wastewater, phenol may decrease the treatment efficiency because of its high concentration and toxicity to microorganisms. Bioaugmentation has been regarded as a good improvement of the traditional biological treatment using isolated degrading strains. In this study, two phenol degrading strains, Pseudomonas sp. PCT01 and PTS02, were isolated and investigated for degradation ability and application to real coking wastewater treatment. RESULTS: Complete phenol degradation was achieved after 18 h inoculation in medium containing 229‐461 mg L^?1 of phenol for both strains. The presence of phenol, pyridine and other compounds in mixed substrate or in coking wastewater prolonged the degradation to 20‐32 h with an initial phenol concentration of 160‐280 mg L^?1. The study of degradation kinetics yielded a two‐stage model to describe the effect of the initial phenol concentration and inhibitory compounds on phenol degradation. The highest degradation rate constant of the second stage, 1.25 h^?1 for PCT01 and 0.75 h^?1 for PTS02, was obtained at low phenol concentration in a single substrate. CONCLUSION: It was found that both strains could degrade phenol effectively and maintain their phenol degradation ability in coking wastewater, and therefore could be used for bioaugmentation treatment of coking wastewater. Copyright © 2011 Society of Chemical Industry     

全国27所医院多重耐药鲍曼不动杆菌及铜绿假单胞菌对12种抗菌药物的敏感性

目的　研究医院感染相关多重耐药鲍曼不动杆菌（multi-drug resistant Acinetobacter baumannii,MDR-AB）及多重耐药铜绿假单胞菌（multi-drug resistant Pseudomonas aeruginosa, MDR-PA）对12种抗菌药物的敏感性。方法　收集2011年8月至2012年7月全国27所教学医院分离的医院感染相关MDR-AB及MDR-PA菌株。所有菌株均分离自有明确感染意义的临床标本，严格排除痰及筛查性拭子。菌株收集后统一在微生物实验室采用微量肉汤稀释法，测定其对12种抗菌药物的最小抑菌浓度（minimum inhibitory concentration，MIC），并同时用CLSI M100-S24及M100-S23/S21鲍曼不动杆菌和铜绿假单胞菌的碳青霉烯类新旧折点进行对比分析。结果　本研究共收集到MDR-AB 664株，未发现全耐药鲍曼不动杆菌；收集到MDR-PA 268株，其中有4株全耐药铜绿假单胞菌。外科病房及ICU病房是多重耐药菌株的主要来源。MDR-AB对黏菌素的敏感率最高，为96.8%；替加环素的敏感率为72.6%，其余药物的敏感率均低于55%。MDR-PA对黏菌素的敏感率仅为72.4%，但对阿米卡星的敏感率（64.2%）明显高于MDR-AB（16.7%）。在CLSI折点改变后，MDR-AB对亚胺培南及美罗培南的敏感率仅分别下降了1.3%和0.6%，但MDR-PA对亚胺培南及美罗培南的敏感率分别下降了5.5%和8.6%。ICU病房来源的MDR-AB及MDR-PA对碳青霉烯酶类药物敏感率都明显低于外科及其他病房。不同地域来源多重耐药菌株的耐药谱有所差异。结论　黏菌素和替加环素对MDR-AB有良好的抗菌活性，黏菌素及阿米卡星对MDR-PA抗菌活性较好。     

Structures of the N-Terminal Domain of PqsA in Complex with Anthraniloyl- and 6-Fluoroanthraniloyl-AMP: Substrate Activation in Pseudomonas Quinolone Signal (PQS) Biosynthesis

Pseudomonas aeruginosa, a prevalent pathogen in nosocomial infections and a major burden in cystic fibrosis, uses three interconnected quorum-sensing systems to coordinate virulence processes. At variance with other Gram-negative bacteria, one of these systems relies on 2-alkyl-4(1H)-quinolones (Pseudomonas quinolone signal, PQS) and might hence be an attractive target for new anti-infective agents. Here we report crystal structures of the N-terminal domain of anthranilate-CoA ligase PqsA, the first enzyme of PQS biosynthesis, in complex with anthraniloyl-AMP and with 6-fluoroanthraniloyl-AMP (6FABA-AMP) at 1.4 and 1.7 Å resolution. We find that PqsA belongs to an unrecognized subfamily of anthranilate-CoA ligases that recognize the amino group of anthranilate through a water-mediated hydrogen bond. The complex with 6FABA-AMP explains why 6FABA, an inhibitor of PQS biosynthesis, is a good substrate of PqsA. Together, our data might pave a way to new pathoblockers in P. aeruginosa infections.     

Antimicrobial packaging of raw beef,pork and turkey using silver‐zeolite incorporated into the material

This study determined the efficacy of silver‐zeolite impregnated into wrapping paper to reduce the bacterial growth on raw beef, pork and turkey cuts. This was compared with that of regular butcher paper. The samples were inoculated with Pseudomonas putida (psychrotrophic spoilage bacterium) and stored on 4% silver‐zeolite and regular butcher paper for up to 4 days at 4 °C and 10 °C. Results showed that P. putida on the beef, pork and turkey samples did not increase in numbers after exposure to all paper packaging at 4 °C during the 4 days of storage. At 10 °C storage temperature, logarithmic growth patterns for the organisms were seen on all paper packaging. However, the growth rate was slower for the organisms on the silver‐zeolite paper. Storage on the silver‐zeolite paper accounted for one log cfu/sample mean reduction in viable cell count for the beef, pork and turkey samples when compared with the samples stored on the butcher paper at 3 days.     

Chemical Signals of Synthetic Disaccharide Derivatives Dominate Rhamnolipids at Controlling Multiple Bacterial Activities

Microbes secrete molecules that modify their environment. Here, we demonstrate a class of synthetic disaccharide derivatives (DSDs) that mimics and dominates the activity of naturally secreted rhamnolipids by Pseudomonas aeruginosa. The DSDs exhibit the dual function of activating and inhibiting the swarming motility through a concentration‐dependent activity reversal that is characteristic of signaling molecules. Whereas DSDs tethered with a saturated farnesyl group exhibit inhibition of both biofilm formation and swarming motility, with higher activities than rhamnolipids, a saturated farnesyl tethered with a sulfonate group only inhibits swarming motility but promote biofilm formation. These results identified important structural elements for controlling swarming motility, biofilm formation, and bacterial adhesion and suggest an effective chemical approach to control intertwined signaling processes that are important for biofilm formation and motilities.     

海洋环境中假单胞菌对聚氨酯清漆涂层分解的影响

目的 研究在海洋环境中假单胞菌对聚氨酯清漆涂层分解作用的影响。方法 将聚氨酯清漆涂层样品分别浸泡于无菌海水与含假单胞菌的海水中,对浸泡环境不同的样品利用电化学阻抗谱（EIS）评价涂层防腐性能,使用扫描电子显微镜（SEM）和傅里叶变换红外光谱（FTIR）,观察对比涂层的表面形貌,并表征其分子结构变化。结果 1 h~35 d时,在无菌海水及假单胞菌海水中,样品Nyquist图的容抗弧直径以及Bode图的低频端阻抗模量均减小。与此同时,假单胞菌海水中浸泡样品的Nyquist图容抗弧直径与Bode图低频端阻抗模量的减小量明显大于无菌海水中的减小量。无菌海水浸泡的等效电路在1~48 h时为1个时间常数,5~35 d时增加为2个时间常数;假单胞菌海水浸泡的等效电路在1~48 h时只有1个时间常数,5~29 d时为2个时间常数,35 d时增加为3个时间常数。浸泡36 h时,无菌海水中浸泡样品的涂层电阻值为8.23× 107 Ω?cm2,而假单胞菌海水中样品的涂层电阻为5.14×107 Ω?cm2;至35 d时,无菌海水中样品的涂层电阻降为5.61×106 Ω?cm2,假单胞菌海水中样品的涂层电阻降至7.03×105 Ω?cm2。假单胞菌海水中样品的涂层电阻在36 h~35 d的减小量明显大于无菌海水中的减小量。由SEM结果可以观察到,浸泡30 d后,无菌海水中浸泡样品的表面光滑完整,而在含假单胞菌海水中的样品表面附着了大量细胞及其代谢产生的生物膜,并出现了大量微孔与粉化痕迹。通过FTIR结果可以发现,浸泡在假单胞菌海水中的样品的N—H和醚基中的C—O含量明显比无菌海水中浸泡的样品要低。结论 电化学结果表明,假单胞菌显著降低了涂层的腐蚀抗性,并导致了涂层的分解。SEM和FTIR的分析结果证明,假单胞菌通过破坏聚氨酯分子中的N—H和醚基中的C—O,造成了涂层的分解。     

一项微生物能力验证的多种方法检测结果分析

为确保微生物能力验证结果的准确报出,本实验室采用了多种方法进行CNAS T 0710的铜绿假单胞菌(Pseudomonas aeruginosa)和金黄色葡萄球菌(Staphylococcus aureus)的能力验证比对检验,结果表明:以上多种检测方法的测试结果相吻合,均显示5份样品中有2份检出铜绿假单胞菌,2份检出金黄色葡萄球菌。最终5份样品测试均取得满意结果,在分析比较中也总结出各种检验方法的优缺点。