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1.
假单胞菌荧光与非荧光铁载体对铁离子的应答差异   总被引:2,自引:0,他引:2       下载免费PDF全文
假单胞菌既能产荧光铁载体也能产非荧光铁载体.通过对假单胞菌在不同铁离子浓度下,在通用CAS(Chrome azroul S)检测平板、改进的蔗糖-天冬氨酸(SA)平板(MSA)上以及通用液体CAS培养基和MSA培养基内的铁载体产生情况的比较,发现在通用CAS的液体培养基上产生的主要为非荧光铁载体(pyochelin),而在改进的MSA培养基上产生的主要为荧光铁载体(pyoverdine);在铁离子的应答方面,pyoverdine较pyochelin灵敏,较低的铁离子浓度即可抑制荧光铁载体的产生,但是不能抑制非荧光铁载体.  相似文献   

2.
Under iron stress, Legionella pneumophila secretes legiobactin, a nonclassical siderophore that is reactive in the chrome azurol S (CAS) assay. Here, we have optimized conditions for legiobactin expression, shown its biological activity, and identified two genes, lbtA and lbtB, which are involved in legiobactin production. lbtA appears to be iron repressed and encodes a protein that has significant homology with siderophore synthetases, and FrgA, a previously described iron-regulated protein of L. pneumophila. lbtB encodes a protein homologous with members of the major facilitator superfamily of multidrug efflux pumps. Mutants lacking lbtA or lbtB were defective for legiobactin, producing 40 to 70% less CAS reactivity in deferrated chemically defined medium (CDM). In bioassays, mutant CDM culture supernatants, unlike those of the wild type, did not support growth of iron-limited wild-type bacteria in 2',2'-dipyridyl-containing buffered charcoal yeast extract (BCYE) agar and a ferrous iron transport mutant on BCYE agar without added iron. The lbtA mutant was modestly defective for growth in deferrated CDM containing the iron chelator citrate, indicating that legiobactin is required in conditions of severe iron limitation. Complementation of the lbt mutants restored both siderophore expression, as measured by the CAS assay and bioassays, and bacterial growth in deferrated, citrate-containing media. The lbtA mutant replicated as the wild type did in macrophages, amoebae, and the lungs of mice. However, L. pneumophila expresses lbtA in the macrophage, suggesting that legiobactin, though not required, may play a dispensable role in intracellular growth. The discovery of lbtAB represents the first identification of genes required for L. pneumophila siderophore expression.  相似文献   

3.
CAS平板覆盖法检测氢氧化细菌铁载体   总被引:3,自引:1,他引:2  
【目的】用CAS平板覆盖法检测氢氧化细菌铁载体,解决通用CAS琼脂平板法中十六烷基三甲基溴化铵对真菌和某些细菌的生长抑制问题。【方法】将改良的CAS检测培养基覆盖在长满菌落的无铁培养基上,生长抑制问题因微生物未与十六烷基三甲基溴化铵直接接触而解决。【结果】3株氢氧化细菌SDW-5、SDW-9和AaP-13均能产生单菌落,加入CAS检测培养基1 h后,菌落周围产生明显的铁载体晕圈。【结论】本方法成功解决了生长抑制问题,可以作为检测微生物铁载体的通用方法。  相似文献   

4.
A lead-resistant bacterial strain 4EA from soil contaminated with car battery waste from Goa, India was isolated and identified as Pseudomonas aeruginosa. This lead-resistant bacterial isolate interestingly revealed lead-enhanced siderophore (pyochelin and pyoverdine) production up to 0.5 mM lead nitrate whereas cells exhibit a significant decline in siderophore production above 0.5 mM lead nitrate. The bacterial cells also revealed significant alteration in cell morphology as size reduction when exposed to 0.8 mM lead nitrate. Enhanced production of siderophore was evidently detected by chrome azurol S agar diffusion (CASAD) assay as increase in diameter of orange halo, and reduction in bacterial size along with significant biosorption of lead was recorded by scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX). Pseudomonas aeruginosa strain 4EA also exhibits cross tolerance to other toxic metals viz. cadmium, mercury, and zinc besides resistance to multiple antibiotics such as ampicillin, erythromycin, amikacin, cephalexin, co-trimoxazole, mecillinam, lincomycin, ciphaloridine, oleondamycin, and nalidixic acid.  相似文献   

5.
Nine halophilic archaea viz., Halobacterium salinarum, Halobacterium sp.1, Halobacterium sp.2, Halobaculum sp., Halococcus saccharolyticus, Halorubrum saccharovorum, Haloterrigena turkmenica, Halogeometricum sp. and Natrialba sp. isolated from marine salterns around Bhavnagar coast were screened for siderophore production. Five isolates viz., Halococcus saccharolyticus, Halorubrum saccharovorum, Haloterrigena turkmenica, Halogeometricum sp. and Natrialba sp. produced siderophores as evidenced by positive reaction in FeCl3 test, CAS assay and CAS agar plate test. Determination of chemical nature of siderophores by chemical assays and bioassays identified them as carboxylates. Quantification of siderophores indicated Halorubrum saccharovorum to be the maximum siderophore producer (2.62 RE mg/ml) and Halococcus saccharolyticus to be the least (1.33 RE mg/ml). The present study is the first report on siderophore production in Indian haloarchaeal strains. Mechanism of iron assimilation in four non-siderophore isolates still needs to be investigated further.  相似文献   

6.
AIMS: To evaluate the suitability of chrome azurol S (CAS) agar plate assay as a quantitative methodology for siderophore production. METHODS AND RESULTS: Aspergillus species (A. flavus, A. niger, A. tamarii) were inoculated in the CAS-agar plates and the siderophores production was determined and expressed as CAS-reaction rate (mm per day). All the species showed positive CAS reaction with different rates depending on culture conditions and A. flavus showed the highest CAS-reaction rate. The siderophore production in solid medium expressed as CAS-reaction rate was correlated with siderophore production in liquid medium. CONCLUSIONS: The use of CAS-agar plate assay was modified and the evaluation of CAS reaction in mm per day made it possible to study and quantify the effect of several variables on the siderophore production by Aspergillus fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: We describe the CAS-agar plate assay as a quantitative methodology, which make it possible to select and evaluate the siderophore production by several microorganisms (fungi and bacteria) according to different culture conditions.  相似文献   

7.
A well-known and widely used method for detection of siderophore production by microorganisms in solid medium is the universal chrome azurol S (CAS)-agar plate assay. However, the high toxicity of CAS-blue agar medium caused by the presence of a detergent impedes its utilization with many varieties of fungi and Gram-positive bacteria. To solve this problem, a modification of the CAS-agar plate assay was made by incorporating the CAS-blue dye in a medium with no contact with the microorganisms tested. Half of each plate used in our experiments was filled with the most appropriate culture medium for each type of microorganism and the other half with CAS-blue agar. This modification allowed us to study several strains of fungi (basidiomycetes, deuteromycetes, ascomycetes and zygomycetes) and bacteria (Gram positive and negative), some of them appearing for the first time in the literature. All the microorganisms grew properly and reacted in different manners to the CAS assay. Some strains of wood-decaying basidiomycetes (mainly white-rot fungi) and Aspergillus species produced the fastest color-change reactions in the CAS-blue agar. This modified method could facilitate optimization of culture conditions, since both CAS-blue agar and growth medium were prepared and added in the Petri plate separately.  相似文献   

8.
高灵敏假单胞菌铁载体的平板检测方法   总被引:6,自引:1,他引:5  
CAS蓝色检测平板是一种筛选、检测各类细菌铁载体的常用方法,而蔗糖-天冬酰氨培养基被用于假单胞菌产铁载体规律的研究。用天冬氨酸替代天冬酰氨,将CAS蓝色检测液与蔗糖-天冬氨酸培养基(MSA培养基)相结合,得到一种改进的MSA-CAS检测平板。通过对假单胞菌属7个种8个株进行荧光与非荧光铁载体检测方面的比较研究,结果表明MSA-CAS检测平板假单胞菌铁载体的检测灵敏度比通用CAS检测平板高,而且在检测荧光铁载体方面具有荧光背景低、荧光铁载体晕圈明显和晕圈与背景的对比度大的优点。  相似文献   

9.
Universal chemical assay for the detection and determination of siderophores   总被引:145,自引:0,他引:145  
A universal method to detect and determine siderophores was developed by using their high affinity for iron(III). The ternary complex chrome azurol S/iron(III)/hexadecyltrimethylammonium bromide, with an extinction coefficient of approximately 100,000 M-1 cm-1 at 630 nm, serves as an indicator. When a strong chelator removes the iron from the dye, its color turns from blue to orange. Because of the high sensitivity, determination of siderophores in solution and their characterization by paper electrophoresis chromatography can be performed directly on supernatants of culture fluids. The method is also applicable to agar plates. Orange halos around the colonies on blue agar are indicative of siderophore excretion. It was demonstrated with Escherichia coli strains that biosynthetic, transport, and regulatory mutations in the enterobactin system are clearly distinguishable. The method was successfully used to screen mutants in the iron uptake system of two Rhizobium meliloti strains, DM5 and 1021.  相似文献   

10.
Thirty-one bradyrhizobial and rhizobial strains infecting pigeon pea were screened for siderophore production using Chrome Azurol S (CAS) agar plate as well as a CAS assay solution. Of a total of 31 strains only 23 showed siderophore production. Of the 23 siderophore-positive strains, 21 strains showed the production of hydroxamate while 6 strains showed the presence of catechol type of siderophore. A large variation in the quantity of hydroxamate and catechol produced by different rhizobial strains was observed (1.03–3.73 μg hydroxamate N per mg protein; 0.19–3.43 μmol/L of catechol per mg protein). Maximum nodule biomass was produced by strain PP-11 (CC-1020); strain G-14 formed minimum nodule biomass. Nitrogen contents of low, moderate and high siderophore-producing strains were 11.4, 15.4, 20.9 mg per plant, respectively, iron contents were 1445, 1768 and 2003 ppm, respectively. Siderophore production was related to N2-fixing efficiency.  相似文献   

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