An alternative physiological role for the EmhABC efflux pump in Pseudomonas fluorescens cLP6a.
An alternative physiological role for the EmhABC efflux pump in Pseudomonas fluorescens cLP6a.
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DOI：
10.1186/1471-2180-11-252
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发表时间：
2011-11-15
期刊：
影响因子：
4.2
通讯作者：
Foght JM
中科院分区：
文献类型：
--
作者：
Adebusuyi AA;Foght JM
外排泵属于细菌中的抗性-结节-分裂(RND)超家族，与抗生素耐药性和溶剂耐受性有关，但其生理作用尚不清楚。EmhABC是荧光假单胞菌cLP6a中的一种RND型外排泵，它分泌疏水抗生素、染料和包括菲在内的多环芳烃。测定了温度、抗生素等物理化学因素对EmhABC活性和表达的影响，以推测EmhABC在菌株cLP6a中的生理作用(S)，并与EmhB干扰菌株cLP6a-1进行比较。用~(14)C-菲进行的外排实验表明，EmhABC活性受培养温度的影响。与28℃培养的细胞相比，10℃培养的cLP6a细胞菲排出增加，35℃培养的细胞菲排出减少。生长温度的变化和四环素的存在显著改变了cLP6a细胞的膜脂肪酸。在35°C培养的cLP6a细胞中，膜脂肪酸的改变和膜通透性的增加与emhABC的表达增加约30倍相关，并与细胞外游离脂肪酸的增加有关。与菌株cLP6a-1相比，EmhABC的存在促进了荧光假单胞菌cLP6a在超适温度下的生长。综上所述，这些观察结果表明EmhABC外排泵可能参与了膜应激效应的管理，例如由于不利的孵化温度所造成的影响。膜损伤或磷脂代谢导致的脂肪酸外流可能是荧光假单胞菌cLP6a中EmhABC外排泵的主要生理作用。
Efflux pumps belonging to the resistance-nodulation-division (RND) superfamily in bacteria are involved in antibiotic resistance and solvent tolerance but have an unknown physiological role. EmhABC, a RND-type efflux pump in Pseudomonas fluorescens strain cLP6a, extrudes hydrophobic antibiotics, dyes and polycyclic aromatic hydrocarbons including phenanthrene. The effects of physico-chemical factors such as temperature or antibiotics on the activity and expression of EmhABC were determined in order to deduce its physiological role(s) in strain cLP6a in comparison to the emhB disruptant strain, cLP6a-1. Efflux assays conducted with 14C-phenanthrene showed that EmhABC activity is affected by incubation temperature. Increased phenanthrene efflux was measured in cLP6a cells grown at 10°C and decreased efflux was observed at 35°C compared with cells grown at the optimum temperature of 28°C. Membrane fatty acids in cLP6a cells were substantially altered by changes in growth temperature and in the presence of tetracycline. Changed membrane fatty acids and increased membrane permeability were associated with ~30-fold increased expression of emhABC in cLP6a cells grown at 35°C, and with increased extracellular free fatty acids. Growth of P. fluorescens cLP6a at supra-optimal temperature was enhanced by the presence of EmhABC compared to strain cLP6a-1. Combined, these observations suggest that the EmhABC efflux pump may be involved in the management of membrane stress effects such as those due to unfavourable incubation temperatures. Efflux of fatty acids replaced as a result of membrane damage or phospholipid turnover may be the primary physiological role of the EmhABC efflux pump in P. fluorescens cLP6a.
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