大环内酯类抗生素微生物降解的研究进展

大环内酯类抗生素是一类以大环内酯为母核的广谱抗生素。近些年,由于人们对其不规范的生产和使用,抗生素污染成为了重要的环境问题。大量研究表明,微生物降解是现阶段处理抗生素污染的最理想方法。为进一步推动大环内酯类抗生素生物降解的研究,文中概述了大环内酯类抗生素的环境污染现状、微生物降解菌株、降解酶、降解途径和降解大环内酯类抗生素的微生物处理方法,并对大环内酯类抗生素生物降解亟待解决的瓶颈问题进行了讨论,以期为微生物降解后续研究提供参考。     

酵母甾醇转运蛋白研究进展

甾醇是一类广泛存在于生物体内的环戊烷骈多氢菲衍生物,其不仅是细胞膜的重要组成成分,还具有重要的生理和药理活性。随着合成生物学和代谢工程技术的发展,近些年来应用酵母细胞异源合成甾醇的研究不断深入。但由于甾醇是疏水性大分子,倾向于积累在酵母的膜结构中而引发细胞毒性,一定程度上限制了甾醇产量的进一步提升。因此,揭示酵母中甾醇转运机制,特别是与甾醇转运相关的转运蛋白的工作原理,有助于设计新的策略,解除酵母细胞工厂中的甾醇积累毒性、实现甾醇增产。酵母中甾醇转运主要通过蛋白质介导的非囊泡运输机制来完成,本文归纳了酵母中已报道的5类甾醇转运相关蛋白,即OSBP/ORPs家族蛋白、LAM家族蛋白、NPC样甾醇转运蛋白、ABC转运家族蛋白和CAP超家族蛋白,汇总了这些蛋白对细胞内甾醇梯度分布和稳态维持所起的重要作用。此外,本文还综述了甾醇转运蛋白在酵母细胞工厂中的应用现状。     

氟喹诺酮类抗生素及耐药基因污染控制的研究进展北大核心CSCD

氟喹诺酮类抗生素属于喹诺酮类抗生素,是一类人畜通用的抗生素。近年来,被广泛应用于人类和畜牧、水产等养殖业领域,然而其大量使用,造成在环境中的不断残留和累积,给自然环境和人类健康造成了较大威胁。现有研究表明,微生物降解是有效去除氟喹诺酮类抗生素残留污染的有效方法之一。本文总结和介绍了近年来氟喹诺酮类抗生素微生物降解单株菌和混合菌群、微生物降解酶、降解途径以及微生物降解氟喹诺酮类抗生素的实际应用,并对目前氟喹诺酮类抗生素微生物降解研究中存在的问题进行了分析,以及对未来氟喹诺酮类抗生素微生物降解研究的重点进行了探讨,以期为后续的研究提供参考。     

微生物技术去除抗生素残留污染的研究进展

抗生素进入环境会对生物造成深远的影响,如何去除抗生素的残留引起许多国家的关注。抗生素在环境中主要发生生物降解,而具有抗性的微生物菌株发挥主要的功效,因此近些年利用微生物技术处理抗生素残留污染成为研究热点。本文对具有抗生素降解功能的微生物资源和利用复合菌系处理抗生素残留的生物技术进行概括总结,并对微生物处理技术的不足和发展方向进行展望。     

土壤环境中典型抗生素残留及其与微生物互作效应研究进展

抗生素大量不规范使用,其残留对环境和人类健康造成严重威胁。污水灌溉和生物有机肥的施用使土壤成为抗生素的主要归趋地之一,抗生素残留对土壤微生物产生不同程度的影响。首先综述了土壤抗生素污染现状,进一步论述了土壤抗生素残留对抗性基因诱导和微生物群落结构的影响,重点介绍了微生物方法在去除抗生素污染方面的重要作用,并指出了土壤抗生素污染研究中存在的问题,对今后主要研究方向进行展望。     

环境中雌激素的微生物降解

环境中的雌激素是一类重要的环境内分泌干扰物,微生物降解是去除环境雌激素的主要途径。通过归纳已报道的雌激素降解细菌、总结其降解雌激素的机制、分析雌激素降解途径以及其他真核微生物的雌激素降解作用4个方面,概括阐述了雌激素的微生物降解作用,并对未来的研究方向提出展望。     

环境中拟除虫菊酯类农药微生物降解技术研究进展

近年来,随着拟除虫菊酯类农药的大量及不合理使用,环境及食品中的农药残留对人类健康造成的负面影响日益显著。微生物降解农药作为去除农药污染安全高效的方法已成为当前研究热点之一。综述了国内外拟除虫菊酯类农药微生物降解菌的种类、降解机制、降解酶及降解菌应用的最新研究进展,并对亟须解决的重要问题进行了展望。     

海洋来源小单孢菌Micromonospora rosaria SCSIO N160中大环内酯类化合物的分离鉴定

放线菌SCSIO N160是从南海海底沉积物中分离到的一株小单孢菌.从Micromonospora rosaria SCSIO N160的发酵液中,我们分离纯化了四个大环内酯类抗生素,通过质谱与核磁共振1H、13C NMR谱的解析,确定为rosamicin(1)、6108B(2)、M-4365 A1(3)和M4365-G1 (4).     

微生物降解磺胺甲恶唑的研究进展

抗生素是一类难降解、低浓度就有高生态毒性效应的化合物,近年来被归为新型环境污染物,其环境残留与去除备受关注。作为广泛使用的抗生素之一,磺胺甲恶唑在水土环境中的残留量不断增加,检出率也越来越高。研究表明,磺胺甲恶唑是少数几种可被微生物降解的抗生素之一,微生物降解法是最具潜力的残留磺胺甲恶唑去除手段。本文总结了磺胺甲恶唑在土壤、沉积物、活性污泥、混合菌群、酶等条件下的降解及已分离的具有降解能力的单菌株对磺胺甲恶唑的降解情况,包括其降解效率、降解条件等,归纳了目前磺胺甲恶唑微生物降解的主要分类,并讨论了影响磺胺甲恶唑降解的两个特有因素。指出从分子生物学及生物信息学角度研究其降解途径,降解菌、降解菌群的人工构建及其在含磺胺甲恶唑污水处理中的应用与效果评价等应为今后磺胺甲恶唑生物降解与应用研究的重点。     

二苯醚类除草剂的微生物降解研究进展

二苯醚类除草剂是一类广谱、高效、高选择性的除草剂,广泛应用于大豆、花生等农田一年生和多年生阔叶杂草的防除。由于该类除草剂不易降解,多年连续使用会导致其在土壤环境中的大量积累。本文概述了二苯醚类除草剂的基本结构及其对生物的影响,总结了降解二苯醚类除草剂的微生物种类、降解途径和降解过程中关键酶及其基因,分析了影响微生物降解二苯醚类除草剂的因素,对二苯醚类除草剂微生物降解未来的研究方向进行了展望,为深入研究二苯醚类除草剂的生物降解提供参考。     

微生物木糖发酵产乙醇的代谢工程

利用木质纤维素发酵生产乙醇具有广泛的应用前景。而自然界中缺少有效转化木糖为乙醇的微生物是充分利用纤维素水解产物、提高乙醇产率、降低生产成本的关键因素。多年来研究者利用分子生物学技术对微生物菌株进行了代谢工程改造,使其能更有效地利用木糖生产乙醇。以下主要对运动发酵单胞菌、大肠杆菌和酵母等候选产乙醇微生物的木糖代谢工程研究进展进行了概述。     

产油微生物利用餐厨垃圾生产油脂的研究进展

餐厨垃圾中含有丰富的营养物质,经生物转化过程可以合成对人类有用的化学品.某些产油微生物可以处理餐厨垃圾生产油脂,同时合成高附加值代谢产物如多不饱和脂肪酸、角鲨烯和类胡萝卜素等.这不仅能够降低生产成本,而且提高了产物的经济价值,具有极大的工业化应用潜力.文中主要概括了目前餐厨垃圾的处理研究现状,综述了产油微生物发酵餐厨垃...     

Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

The role of the carboxyl and amino groups of polyene macrolides in their interactions with sterols and their selective toxicity. A P-NMR study

The permeability induced by amphotericin B and vacidin A derivatives in large unilamellar lipidic vesicles containing various sterols has been studied using the proton-cation exchange method and ³¹P-NMR spectroscopy. Derivatives which have a free ionizable carboxyl group induce biphasic ‘all or none’ permeability typical of channel-forming ionophores, whatever the sterol present. In sterol-free membranes, they have no significant activity. Derivatives which lack a free ionizable carboxyl group exhibit this channel-like mode of action only in membranes containing ergosterol or sterols with an alkyl side like that of ergosterol. In membranes containing cholesterol or sterol whose side-chain is alike, a slow and progressive permeability is observed at high concentrations. This activity is observed in sterol-free membranes as well. Derivatives containing sugars with substituted amino groups always have lower ionophoric activity than those which are unsubstituted. The greatest decrease in activity was observed for N-acetyl derivatives. Substitution of the amino groups has no effect on the mode of action. A model of interaction of polyenes with sterols is presented accounting for the data obtained on vesicles and the observed selective toxicity of polyene derivatives in biological membranes.     

Studies on the production of actinomycin-D by Streptomyces griseoruber– a novel source

Aims:  To isolate and characterize bioactive metabolites produced by a micro-organism isolated from a soil sample associated with the roots of a medicinal plant, Azadirachta indica .
Methods and Results:  Morphological, cultural, physiological and 16S rRNA homology studies revealed that the organism showed 99% similarity with Streptomyces griseoruber NBRC 12873. One bioactive metabolite (Py2) isolated from the fermented broth was characterized as actinomycin-D (act-D). It showed high activity against various Gram-positive and Gram-negative bacterial cultures, Mycobacterium tuberculosis H37Rv and human neoplastic cells in vitro using standard protocols.
Conclusions:  The isolated strain S. griseoruber produced act-D predominantly (210 mg l⁻¹, c. 88% of the crude) under nonoptimized growth conditions.
Significance and Impact of the Study:  Streptomyces griseoruber may be exploited as a potential source for the commercial production of act-D, as this strain is not reported to produce act-D. Further investigations on the strain for commercial application will be of immense pharmaceutical importance.     

Genetic engineering of doxorubicin production in Streptomyces peucetius: a review

The genetics and biochemistry of daunorubicin and doxorubicin production by Streptomyces peucetius is reviewed, with a focus on how such information can be used for the genetic engineering of strains having improved titers of these two antitumor antibiotics. Received 23 February 1999/ Accepted in revised form 22 March 1999     

Transbilayer distribution of sterols in mycoplasma membranes: a review

The polyene antibiotic, filipin, binds to 3 beta-hydroxysterols. The initial rate of filipin-sterol association, monitored in a stopped-flow spectrophotometer, was first order in each reacting partner. The ratio of rate constants in intact mycoplasma cells relative to isolated, unsealed membranes provides an estimate of sterol distribution in the membrane bilayer. Cholesterol is distributed symmetrically in the bilayer of M. gallisepticum cells from the early exponential phase. However, in the M. capricolum membrane two-thirds of the unesterified cholesterol is localized in the outer leaflet; alkyl-sterols are distributed predominantly in the external monolayer. Cholesterol is translocated rapidly in the bilayer of M. capricolum cells. Exogenous phospholipids incorporated into the membrane had no effect on the cholesterol distribution in M. capricolum.     

Enabling glucose/xylose co-transport in yeast through the directed evolution of a sugar transporter

The capacity to co-transport glucose and xylose into yeast has remained a technical challenge in the field. While significant efforts have been made in transporter engineering to increase xylose transport rates, glucose-based inhibition still limit most of these transporters. To address this issue, we further engineer sugar transporter proteins to remove glucose inhibition and enable glucose/xylose co-transport. Specifically, we start with our previously derived CiGXS1 FIM mutant strain and subjugate it to several rounds of mutagenesis and selection in a hexose metabolism null strain. Through this effort, we identify several mutations including N326H, a truncation in the C-terminal tail, I171F, and M40V as additionally dominant for reducing glucose inhibition. The resulting transporter shows substantially improved xylose transport rates in the presence of high quantities of glucose including up to 70 g/L glucose. Moreover, the resulting transporter enables co-utilization of glucose and xylose with glucose rates on par with a wild-type transporter and xylose rates exceeding that of glucose. These results demonstrate that major facilitator superfamily hexose transporters can be rewired into glucose-xylose co-transporters without functional inhibition by either substrate. These results enhance the potential of using lignocellulosic biomass as a feedstock for yeast.     

Pest management services through conservation of biological control agents: review,case studies and field experiences

ABSTRACT

Conservation biological control is an approach to enhance the efficacy of natural enemies by ensuring their availability in an agro-ecosystem on a long temporal scale. An increased survival often leads to better fecundity and improved behaviour of the natural enemies, which in turn ensures sustainable pest management. This paper, apart from being a concise review of conservation biological control, deals with selected India-specific case studies and field experiences on habitat manipulation and refugia. Results from a Bengaluru-based study during 2012–2015 on conservation biological control in an organic mango ecosystem are also presented. It also dwells briefly on conservation of insectivorous birds and touches upon conservation biocontrol with respect to entomopathogenic microorganisms and plant disease antagonists.